Tesi sul tema "Laser cascade quantique"
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Chassagneux, Yannick. "Photonique pour les lasers à cascade quantique térahertz". Phd thesis, Université Paris Sud - Paris XI, 2009. http://tel.archives-ouvertes.fr/tel-00740111.
Grouiez, Bruno Parvitte Bertrand Zéninari Virginie. "Applications des lasers à cascade quantique pulsés à l'étude de l'atmosphère". Reims : S.C.D. de l'Université, 2008. http://scdurca.univ-reims.fr/exl-doc/GED00000980.pdf.
Laffaille, Pierre. "Lasers à cascade quantique moyen infrarouge à base d'InAs". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2013. http://tel.archives-ouvertes.fr/tel-01021281.
Grouiez, Bruno. "Applications des lasers à cascade quantique pulsés à l’étude de l’atmosphère". Reims, 2008. http://www.theses.fr/2008REIMS025.
This thesis work presents atmospheric applications using Quantum Cascade lasers (QCL) emitting in mid-Infrared. Parts I & II present the context of my thesis work, the principle of QCL and the study of _1 band of SO2 around 9 μm by continuous wave operation QCL. In the third part, we present the first method we have employed to command the laser which is also the most popular in pulsed operation. This one consists of operating the laser with a short pulse duration (_ 10 ns). This method has been applied to the study of NH3 and has put in evidence many troubles which limit considerably the interest in spectroscopic applications. In the fourth part, the command of QCL using long pulses (> 500 ns) is presented. We demonstrate the possibility to record an intra-pulse spectrum in about one microsecond. This technic has been applied to the study of SO2 in 9 μm region and the results have been compared with results obtained by continuous wave operation. The conclusion of our previous works (in parts III & IV) drove us to consider a third way with intermediatesize pulse width (< 100 ns). This is presented in the fifth part. This method has solved many troubles of this kind of laser and furthermore it has put into the light the most importants points about "rapid passage" effects
Jumpertz, Louise. "Photonique non-linéaire dans les lasers à cascade quantique moyen infrarouges". Electronic Thesis or Diss., Paris, ENST, 2016. https://pastel.hal.science/tel-03689516.
Mid-infrared quantum cascade lasers are unipolar semiconductor lasers, which have become widely used sources for applications such as gas spectroscopy, free-space communications or optical countermeasures. Applying external per-turbations such as optical feedback or optical injection leads to a strong modification of the quantum cascade laser prop-erties. Optical feedback impacts the static properties of mid-infrared Fabry-Perot and distributed feedback quantum cas-cade lasers, inducing power increase, threshold reduction, modification of the optical spectrum, which can become either single- or multimode, and enhanced beam quality of broad-area transverse multimode lasers. It also leads to a different dynamical behavior, and a quantum cascade laser subject to optical feedback can oscillate periodically or even become chaotic: this work provides the very first analysis of optical instabilities in the mid-infrared range. A numerical study of optical injection furthermore proves that quantum cascade lasers can injection-lock over a few gigahertz, where they should experience enhanced stability and especially improved modulation bandwidth. Furthermore, some promising dynamics appear outside the locking range with periodic oscillations at a tunable frequency or high-intensity events. A quantum cascade laser under external control could therefore be a source with enhanced properties for the usual mid-infrared applications, but could also address new applications such as tunable photonic oscillators, extreme events gen-erators, chaotic LIDAR, chaos-based secured communications or unpredictable countermeasures
Le, Biavan Nolwenn. "Vers un laser à cascade quantique à base d’oxyde de zinc". Thesis, Université Côte d'Azur (ComUE), 2019. http://www.theses.fr/2019AZUR4070.
The Terahertz domain (THz), situated between the visible and microwave energy range, turns out to be very promissing in terms of applications. However its application potential is not fully used because of the lack for compact sources able to cover a large part of its energy range. Quantum Cascade Lasers (QCL) are good candidates for this purpose, because there are both compact and highly tunable. But in the THz range, the existing QCLs suffer from the operation temperature limitation ( 200K ), which is very restricting from the application viewpoint. It comes from an intrinsic property of the materials commonly used to build QCLs: the LO-phonon energy. As a consequence a strong competition between the LO-phonon transition and the QCL radiative transition arise at room temperature, which hinder the lasing efficiency. To tackle this issue, we choose to make use of ZnO, because its LO-phonon energy is twice larger compared to the aforementioned materials, thus enabling to keep the lasing action efficient at room temperature. Even if ZnO and its related alloys are not new in the field of semiconductor science, they are totally exotic for the QCL field. Indeed, QCL are built from highly periodic heterostructures, from which all the key device properties come from. Therefore, the heterostructure should be controlled at the monolayer scale and this precision should be reproducible on hundred of periods, which made QCL growth an indubitabble challenge. This thesis aims at take up this challenge by bringing ZnO/(Zn, Mg)O heterostructures to this ultime degree of control. We are growing ZnO/(Zn, Mg)O heterostructures on ZnO substrates with a new molecular beam epitaxy system and we demonstrate that the heterostructures quality matche the QCL material requirements. This first step enables us to demonstrate the observation of intersubband transitions in the mid-infrared range until room temperature, as well as their coupling within asymmetric quantum well structures. Complete cascade structures were also grown and lead to the first demonstration of a ZnO based Quantum Cascade Detector in the infrared range until room temperature. QCL structures were also grown and shows very good heterostructure control as stated by scanning transmission electron microscopy experiments
Mammez, Marie-Hélène. "Détection hétérodyne de molécules d'intérêt atmosphérique à l'aide de lasers à cascade quantique". Thesis, Reims, 2016. http://www.theses.fr/2016REIMS027/document.
Infrared heterodyne sensing is a technique which has been developed primarily toimprove the detectivity of infrared detectors, particularly in the 8 − 12 μm window. This technique has long been closely associated with the use of gas lasers. The fields of application were mainly astrophysical and atmospheric studies. Due to the complexity of implementation and the size of this type of instrument, ew other applications could have been envisaged. Recent progress in the field of semiconductor lasers (Quantum Cascade Laser - QCL - cover a large part of the infrared spectrum) enable to consider new developments and new applications for infrared heterodyne sensing, for example for the remote detection and identification of atmospheric molecules, such as pollutants. The main advantages of heterodyne sensing concern spectral and directional selectivity of the instrument. It is applicable in civil sector to atmospheric molecules such as ozone and carbon dioxide, and for the military one to detect hazardous species. A heterodyne receiver has been developed with a QCL emitting at around 10 μm and a temperature stabilized black body. To this end, several systems were considered: a system based on lens, another one based on off-axis parabolic mirrors and a last one based on mid-infrared optical fibers. Meanwhile, a heliostat has also been developed in order to do atmospheric measurements
Loghmari, Zeineb. "Lasers à cascades quantiques InAs / AISb au-delà de 10µm : émission mono-fréquence et génération du THz par différence de fréquences". Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS088.
Applications such as gas spectroscopy or medical imaging require light sources emitting in the mid- and far infrared (10 µm<λ < 28 µm) as well as in the THz (λ > 60µm). High-performance, continuous wave regime (CW) and single-frequency emission components are essential for this type of application. Quantum cascade lasers (QCLs) are the only sources that can cover this wide range of wavelengths thanks to their inter-sub-band transitions. However, the performance of LCQs in this wavelength range is often limited by non-radiative transitions. The latter generate mechanisms such as photon absorption by TO phonons or electron relaxation by LO phonons. As a result, laser emission in CW and at room temperature becomes particularly difficult. The objective of this thesis is the development of InAs/AlSb LCQs above 10 µm for single-frequency emission and THz generation by frequency difference. A key point in this work is the use of the InAs/AlSb material system. Their advantage is based on the low effective mass. It is 0.023m0 for InAs compared to 0.041m0 for InGaAs and 0.067m0 in GaAs.First, the development of LCQ active regions based on InAs/AlSb emitting at 11µm was carried out. This work made it possible to produce single-frequency DFB sources emitting continuously at 295K and which were used in QEPAS spectroscopy for ethylene sensing. This LCQ has also been transferred to Silicon (Si) substrate. He has demonstrated the world's most efficient LCQ grown directly on Si substrate. The wavelength range ≥ 11µm was also explored. First, by using a dielectric waveguide where this study leads to an active region design at 20µm whose performances exceed the state of the art in the world with continuous operation up to 240K. Then, these technologies were also exploited by using metal-metal waveguides. In this part, the limits of this waveguide were tested. This made it possible to produce a dual-frequency DFB CQL with a metal-metal waveguide emitting two wavelengths in the far infrared for the generation of THz by difference frequency. In this context, the non-linearity of this type of active region has been optimized. The extraction of the THz wave was also studied
Mammez, Dominique. "Détection de molécules gazeuses d’intérêt atmosphérique par spectrométrie infrarouge avec laser à cascade quantique largement accordable". Thesis, Reims, 2013. http://www.theses.fr/2013REIMS003/document.
As the study of the atmosphere is growing strongly in response to environmental issues, the needs in terms of laser sources for spectroscopy of complex molecules require the development of widely tunable sources. The PhD work presented in this manuscript is focused on the implementation of quantum cascade lasers in external cavity (EC-QCL). Part of this work deals with the characterization of a commercial EC-QCL source and its application to gas detection by photoacoustic spectrometry. Measurements were performed on carbon dioxide in exhaled air and butane. The central part of this thesis consists in the development of ECQCL sources based on quantum cascade laser chips from III-V Lab. The aim is to obtain widely tunable sources that can be used for the detection of complex molecules. This includes simulation, design and implementation of external cavity systems. Two EC-QCL sources were implemented. The first one is a pulsed laser emitting around 4,5μm. The second one emits around 7,5μm and is operated at room temperature in continuous wave mode. This laser was used to record the spectra of acetone and phosphoryl chloride
Gilles, Clément. "Optique intégrée pour sources largement accordables moyen-infrarouge". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS009/document.
In the mid-infrared, arrays of distributed feedback quantum cascade lasers have been developed as a serious alternative to obtain extended wavelength operation range of laser-based gas sensing systems. Narrow-linewidth, single mode operation and wide tunability are then gathered together on a single chip with high compactness and intrinsic stability. In order to benefit from this extended wavelength range in a single output beam, the key challenge resides in the combination of different technologies to merge the output of different sources via the use of mid-IR photonic integrated circuits (PIC). The PIC can be split into three main blocks: the passive waveguide platform, the beam combiner and the active/passive coupler. For beam handling and guiding, we report fabrication and characterization of deeply etched InP/InGaAs/InP waveguides with state of the art performances. We fabricate and characterize multiplexers based on echelle and arrayed waveguide gratings on InP and SiGe platforms. A 60-to-1 spectral multiplexer operating in the 7-to-8.5 µm range is demonstrated. An advanced multiplexing scheme using interleaved and cross-order operations is also exposed. Finally, we realize quantum cascade laser arrays on InP and silicon. We design, fabricate and characterize an adiabatic coupler to efficiently and monolithically integrate active and passive waveguides. Heterogenous and hybrid integration are also considered with the demonstration of a tunable source using laser array and InP-based multiplexer
Ferré, Simon. "Nouvelles architectures et optimisations pour la montée en puissance des lasers à cascade quantique moyen infrarouge". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066488/document.
Quantum cascade lasers (QCLs) are semiconductor laser sources able to produce high output power in mid-infrared range. Target applications are remote spectroscopy and optical counter-measure. Their performances are still limited by electronic transport, optical behavior and thermal load dissipation. First, this work has lead to a better comprehension of the features limiting the QCLs performances. Optical and thermal properties of the materials the QCLs are made of have been measured. By simulation, we have shown the impact of the device and submount's geometries on the performances. Second, we have studied some methods to shape the beam in order to increase the luminance of the QCL. We have then demonstrated that coupling with optic fibers, or using tapered QCLs reduces the divergence of the QCL. In addition, we have obtained very high peak and average powers with broad area (BA) QCLs, while keeping a good far-field quality. Finally, we have shown that it is possible to shape the beam emitted by BA QCLs by optical feedback. Lastly, we have proposed new methods to conceive monolithically phase-locked QCL arrays. On top of experimental results on uniform QCL arrays, we have shown the limits of non-uniform arrays. Finally, we have patented a solution based on amorphous silicon antiguides to phase-lock a large number of QCLs
Petitjean, Yoann. "Modélisation dynamique et caractérisation de lasers à cascade quantique Térahertz refroidis à l'hélium liquide". Toulouse, ISAE, 2010. http://www.theses.fr/2010ESAE0020.
Sow, Papa lat tabara. "Développement d'un spectromètre laser à cascade quantique pour des applications en spectroscopie de haute résolution et en métrologie des fréquences". Thesis, Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCD011/document.
This thesis is devoted to the developpement of a laser spectrometer quantum cascade to frequency metrology and high-resolution spectroscopy. The objective of this work is to developp a new tool for projects in our group : Measuring the Boltzman constant and test of non conservation of parity. Thus the new source was characterized by measuring its spectral density noise, amplitude noise and its emission line width. The phase locking of the QCL on the CO2 laser has achived spectroscopy NH and MTO, molecules of interest for the projects of the group mentioned aboive respectively
Ouerghemmi, Ezzeddine. "Étude physique des limites en puissance des lasers à cascade quantique". Phd thesis, Ecole Polytechnique X, 2011. http://pastel.archives-ouvertes.fr/pastel-00605931.
Ouerghemmi, Ezzedine. "Étude physique des limites en puissance des lasers à cascade quantique". Palaiseau, Ecole polytechnique, 2011. http://pastel.archives-ouvertes.fr/docs/00/60/59/31/PDF/manuscrit_ezzeddine_Ouerghemmi.pdf.
This thesis work is devoted to the theoretical and experimental study of the limiting factors of quantum cascade lasers (QCL) output power. It exposes a global modeling of their electro-optical properties. Laser operation is described in particular by including the electronic structure, non-radiative electron scattering mechanisms and the electron-photon coupling along the laser cavity. This model allowed us to successfully reproduce all the characteristics (current and optical power as a function of the applied voltage) of a QCL over the whole range of operating temperatures. This model was used to calculate the electron temperature in QCL. It showed that scattering by LO phonons is the only mechanism by which the gas of electron can transfer energy towards the lattice. Elastic scattering mechanisms are sources of energy for the electron gas. Two physical parameters allow to fully describe the electron temperature in the device: the electronic thermal resistance of the heterostructure and the temperature current coupling factor. Taking into account the electron-photon coupling shows that it may influence the electronic distribution over energy levels. Therefore, the gain of the active zone of the laser is reduced in the presence of this coupling. This effect, called gain saturation, plays an important role on the output performances of QCL. Minimizing this effect can increase the maximum power output of the laser by a factor of two. This study allowed us to propose new design rules of active regions to improve the QCL output performances. The experimental characterization of some of these structures has validated the approach we have followed towards performances improvement
Destic, Fabien. "Imagerie térahertz utilisant des lasers à cascade quantique : application au contrôle non destructif de matériaux". Thesis, Toulouse, ISAE, 2014. http://www.theses.fr/2014ESAE0019/document.
Quantum Cascade Lasers (QCL) are "new" THz sources that have enjoyed remarkable progress in terms of power, operating temperature and beam quality. QCLs are used in continuous wave THz imaging setups applied to Non Destructive Testing of materials. A first qualitative application of NDT allows us to highlight defects in the fibers impregnation by resin or damages caused by an impact on composite materials. Transmission and reflection images at 3.8 THz are compared with a NDT ultrasonic technique. A second quantitative application relates to the water concentration in two hydrophobic polymeric materials: polystyrene and polypropylene. Establishing a relationship between the transmittance of the sample and mass water content enables us to draw up a quantified mapping of the latter. These maps are necessary for the understanding of the water diffusion process in polymeric materials
Dross, Frédéric. "Sources laser à cascade bipolaire pour la modulation directe". Paris, ENST, 2004. http://www.theses.fr/2004ENST0017.
We report on the improvement of the opto-RF link characteristics by the use of directly-modulated bipolar cascade laser sources. A theoretical as well as experimental study enables to improve by a factor n2 the RF link gain with the use of n discrete lasers. In addition, we improve by 3 dB the relative intensity noise of a laser source composed of two discrete lasers. To circumvent bandwidth limitations, we study, through the development of a rate equation model, and through the improvement of a self-consistent transport model, the influence of monolithically cascading several active junctions into a single-transverse-mode bipolar cascade structure. Eventually, the developed models are used to design the component and we present some characterizations. Due to the low tunnel junction conductivity, the device exhibits an important current spreading. In addition, the carrier distribution in the biased cavity increases the optical internal loss. Despite these limitations, we obtain a quantum internal differential efficiency greater than 100% and a single-transverse-mode bipolar cascade laser with enhanced external differential efficiency
Maysonnave, Jean. "Dynamique ultrarapide de lasers à cascade quantique Terahertz - le graphène comme émetteur Terahertz". Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066360/document.
The terahertz (THz) range is a region of the electromagnetic spectrum which lies at the limit between the electronic and optical domain. Currently, THz applications suffer from the lack of sources and detectors. In this context, this thesis focuses on the fundamental study and the development of new functionalities of different THz sources, usingTHz time-domain spectroscopy (TDS) as a base. This powerful tool enables to acquire the temporal profile of a THz electric field and is used to explore the THz emission properties of quantum cascade lasers (QCLs) and graphene.In the first part, the ultrafast response of QCLs is investigated. A phase control of the electric field of THz QCLs via injection seeding is realised and optimised. This enables the measurement of the amplitude and temporal profile of the laser emission. Throughthese experiments and simulations, a quantitative description of the gain dynamics can be accessed. This information is critical for modelocking. Finally, a fast modulation of the gain of QCLs is realized and leads to short pulses generation (15 ps) in a modelocked regime. These studies open the way for using QCLs as powerful sources in TDS.In the second part, THz radiation generation from graphene under optical excitation is demonstrated by a second order non-linear process. The THz emission results from themomentum transfer from the photons to the electrons of graphene (photon drag). As well as broadband THz generation, novel bandstructure properties of graphene can be explored such as the different dynamics between the photogenerated electrons and holes
Ndebeka-Bandou, Camille. "Etude théorique de l'absorption par porteurs libres dans les structures à cascade quantique". Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066185/document.
The demand to produce reliable THz detectors and emitters has lead to a signicant improvement of the Quantum Cascade Lasers (QCLs). First demonstrated in 1994 in the mid-infrared range, these unipolar semiconductor lasers are one of the most promising photonic sources for THz emission. Nevertheless, various optical loss phenomena limit their performances and the improvement of these devices is intensively researched. Among the possible loss sources, the Free Carrier Absorption (FCA), that arises from intra- and inter-subband oblique transitions activated by any disorder source destroying the translational invariance in the layer plane, has to be accurately modeled. FCA is well documented for bulk materials where the semiclassical Drude model can be used. For QCLs, this model predicts FCA coefficients that are comparable or larger than the actual QCL gains. This work presents a quantum modeling of FCA in quantum cascade structures following two theoretical approaches : a perturbative expansion at the first order in the disorder potential and a numerical diagonalization of Hamiltonian in presence of disorder. These calculations show that FCA is very small in QCLs and radically differs from the semiclassical Drude result. Moreover, they point out the different contributions to the absorption spectrum and the possibility of ajusting the absorption linewidth and lineshape by dopant engineering. Important disorder-induced localization effects have been identified as well as their non negligible influence on the electronic scattering rates
Joint, François. "Ultra compact ans sensitive Terahertz Heterodyne receiver based on quantum cascade laser and hot electron bolometer". Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEO025/document.
We demonstrate an ultra-compact Terahertz (THz) heterodyne detec- tion system based on a quantum cas- cade laser (QCL) as local oscillator and a hot electron bolometer (HEB) for the mixing. It relies on a new opti- cal coupling scheme where the local oscillator signal is coupled through the air side of the planar HEB an- tenna, while the signal to be de- tected is coupled to the HEB through the lens. This technique allows us to suppress the beam splitter usu- ally employed for heterodyne mea- surements. The mixer is a Niobium Nitride HEB with a log-spiral planar antenna on silicon and mounted on the back of a plano-convex silicon lens. We have developed a low power consumption and low beam di- vergence 3rd-order distributed feed- back laser with single mode emis- sion at the target frequency of 2.7 THz to be used as local oscillator for the heterodyne receiver. The cou- pling between the QC laser and the the HEB has been further optimized, using a dielectric hollow waveguide that reliably increases the laser beam directivity up to 55 dBi. Upon the high beam quality, sufficient output power in a single mode at the tar- geted frequency and low power dissi- pation of our local oscillator, we have build an ultra compact THz hetero- dyne receiver with sensitivity close to the state of the art at 2.7 THz
Maysonnave, Jean. "Dynamique ultrarapide de lasers à cascade quantique Terahertz - le graphène comme émetteur Terahertz". Electronic Thesis or Diss., Paris 6, 2014. http://www.theses.fr/2014PA066360.
The terahertz (THz) range is a region of the electromagnetic spectrum which lies at the limit between the electronic and optical domain. Currently, THz applications suffer from the lack of sources and detectors. In this context, this thesis focuses on the fundamental study and the development of new functionalities of different THz sources, usingTHz time-domain spectroscopy (TDS) as a base. This powerful tool enables to acquire the temporal profile of a THz electric field and is used to explore the THz emission properties of quantum cascade lasers (QCLs) and graphene.In the first part, the ultrafast response of QCLs is investigated. A phase control of the electric field of THz QCLs via injection seeding is realised and optimised. This enables the measurement of the amplitude and temporal profile of the laser emission. Throughthese experiments and simulations, a quantitative description of the gain dynamics can be accessed. This information is critical for modelocking. Finally, a fast modulation of the gain of QCLs is realized and leads to short pulses generation (15 ps) in a modelocked regime. These studies open the way for using QCLs as powerful sources in TDS.In the second part, THz radiation generation from graphene under optical excitation is demonstrated by a second order non-linear process. The THz emission results from themomentum transfer from the photons to the electrons of graphene (photon drag). As well as broadband THz generation, novel bandstructure properties of graphene can be explored such as the different dynamics between the photogenerated electrons and holes
Ndebeka-Bandou, Camille. "Etude théorique de l'absorption par porteurs libres dans les structures à cascade quantique". Electronic Thesis or Diss., Paris 6, 2014. http://www.theses.fr/2014PA066185.
The demand to produce reliable THz detectors and emitters has lead to a signicant improvement of the Quantum Cascade Lasers (QCLs). First demonstrated in 1994 in the mid-infrared range, these unipolar semiconductor lasers are one of the most promising photonic sources for THz emission. Nevertheless, various optical loss phenomena limit their performances and the improvement of these devices is intensively researched. Among the possible loss sources, the Free Carrier Absorption (FCA), that arises from intra- and inter-subband oblique transitions activated by any disorder source destroying the translational invariance in the layer plane, has to be accurately modeled. FCA is well documented for bulk materials where the semiclassical Drude model can be used. For QCLs, this model predicts FCA coefficients that are comparable or larger than the actual QCL gains. This work presents a quantum modeling of FCA in quantum cascade structures following two theoretical approaches : a perturbative expansion at the first order in the disorder potential and a numerical diagonalization of Hamiltonian in presence of disorder. These calculations show that FCA is very small in QCLs and radically differs from the semiclassical Drude result. Moreover, they point out the different contributions to the absorption spectrum and the possibility of ajusting the absorption linewidth and lineshape by dopant engineering. Important disorder-induced localization effects have been identified as well as their non negligible influence on the electronic scattering rates
Mappe, fogaing Irene. "Mesures par spectrométrie laser des flux de N2O et CH4 produits par les sols agricoles et viticoles". Thesis, Reims, 2013. http://www.theses.fr/2013REIMS017/document.
Since the industrial revolution, emissions of greenhouse gases (GHG) responsible for global warming, mainly anthropogenic, continue to increase. Among these gases, the main concerned are carbon dioxide (CO2 ), nitrous oxide (N2O ) and methane (CH4 ).In my thesis, we will focus mainly on N2O and CH4 , which despite their smaller quantities in the atmosphere, have a global warming potential higher than the CO2. These anthropogenic gas emissions are sufficient to cause climatic change in the short or medium term. It is therefore necessary to understand the phenomena linked to these emissions.Many European networks such as Euroflux, CarboEuroflux, NitroEurope, CarboEurope GHG-Europe and ICOS have actively contributed to the understanding and quantification of greenhouse gases emissions. However it remains considerable uncertainty about the inter-annual balance sheets of these emissions. To better assimilate the temporal variability of N2O and CH4 emissions, it is necessary to measure continuously over time in terms of ecosystems, soil types, and to have performance measurement tools. The GSMA with its expertise in instrumentation, has developed a spectrometer using a quantum cascade laser, QCLAS (Quantum Cascade Laser Absorption Spectrometer), designed to measure in situ gas flow produced by the soil. As in any experiment, QCLAS measurements may be contaminated by noise. These noises can cause biases in fluxes determination. This is why we will focus on signal proccessing methods such as wavelet transform, singular value decomposition, with the purpose of extracting useful signal informations and significantly improving the signal to noise ratio and the dispersion of measurements. This thesis is organized in three main parts: The first part is devoted first to conventional techniques for gas measurements, where we will introduce the instrument QCLAS. Then, we will examine three usual techniques of flow measurement namely: the technique of closed chambers, Eddy correlation and relaxed Eddy accumulation. The second part will focus on the different procedures and treatment methods to optimize experimental measurements. The last part will focus on the various measurements campaigns made with QCLAS. These applications demonstrate the robustness of QCLAS as well as its ability to perform field measurements
Oustinov, Dimitri. "Etude de lasers à cascade quantique par spectroscopie térahertz dans le domaine temporel". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2011. http://tel.archives-ouvertes.fr/tel-00601157.
Renaudat, Saint-Jean Margaux. "Laser à cascade quantique dans un guide micro-onde pour la réalisation d'un peigne de fréquence". Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCC094.
Quantum cascade lasers (QCLs) are unipolar compact devices based on optical transitions in quantum wells between the quantized states of the conduction band. Their emission wavelength, easily tailored thanks to quantum engineering, can cover the entire range of the mid-infrared spectrum. The work presented in this thesis deals with the design and the study of new cavity architectures for the realization of a frequency comb. Aim of the work is to improve the stability and the control of the intermode frequency spacing of Fabry-Perot QCL emitting at 9 ktm. By merging microwave and semiconductor laser technologies, we demonstrate the generation of a stable frequency comb, integrating a microstrip line in the QCL cavity. A comparative study of the new architecture and standard design has been carried out. The stability of the spacing between the modes has been characterized by measuring the microwave component of the optical signal at the round-trip frequency of photons in the cavity (13. 7 GHz). Full width at half maximum of this signal is seventeen times lower than that measured for a standard QCL with similar optical power, evidence of improved stability in the optical cavity. Through the injection of a stable microwave signal at the round-trip frequency, we control and stabilize the frequency comb over a range of the order of MHz with an injected power of 10 mW. The performance of direct modulation of the devices has been also investigated : the measured bandpass of the microstrip laser is three times higher than the standard laser at 10 GHz
Péré-Laperne, Nicolas. "Etude des structures à cascade quantique sous champ magnétique - Application aux lasers THz et aux détecteurs infrarouges". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://tel.archives-ouvertes.fr/tel-00414749.
Simeni, Simeni Marien. "Quantum cascade laser absorption studies of nitric oxide production by nanosecond pulsed discharges in air and in combustible mixtures". Thesis, Châtenay-Malabry, Ecole centrale de Paris, 2015. http://www.theses.fr/2015ECAP0033/document.
Atmospheric pressure plasmas have numerous potential applications. These applications include for instance biomedicine, material processing, environmental biodecontamination and plasma-assisted combustion. The versatility of plasma discharges results from their ability to produce high quantities of active species without increasing the temperature of the gas appreciably. Nanosecond Repetitively Pulsed discharges (NRP) have received great attention owing to their capacity to generate high electron densities, which lead to the creation of a high density of active species such as atomic oxygen. Optical Emission Spectroscopy (OES) showed that excited nitric oxide (NO) was released by NRP discharges in air or in air/fuel mixtures.Although NRP discharges have already been the object of several investigations, the kinetic mechanisms of NO production by NRP discharges at atmospheric pressure remain somewhat unclear. This is one of the motivations for the investigations conducted in this thesis. In addition, NRP discharges were found to produce large amounts of atomic oxygen, which is of great interest for applications such as plasma-assisted combustion. It was shown in particular that thanks to this high production of active species, NRP discharges can effectively stabilize lean flames at atmospheric pressure. However, the production of NO in NRP discharges and in plasma-stabilized flames remains to be investigated. This is the second purpose of this thesis.Absolute and in-situ NO density measurements in atmospheric pressure plasma or/and flame environments are very challenging. Fluorescence-based techniques such as Laser Induced Fluorescence (LIF) require complex calibration methods. These techniques also require the knowledge of the quenching rates of the excited states (particularly at atmospheric pressure), which strongly depend on the temperature, density and nature of the species and can be very different for plasma or/and flame environments. Other techniques, such as chemiluminescence probe sampling also have quenching and calibration issues, and ex-situ UV and IR absorption-based gas analyzers can lead to errors, in particular for radicals.In this study, we developed Quantum Cascade Laser Absorption Spectroscopy (QCLAS) for in-situ nitric oxide absolute density measurements in open-air and in combustion environments. This technique overcomes the difficulties of the previous ones by using high-resolution (10-3 cm-1) rotational-vibrational absorption spectroscopy. This technique presents the advantages of high spectral selectivity, no calibration requirement, and high sensitivity. Two experimental setups were developed to measure NO densities and temperature, (1) within a NRP discharge in air, with 300-µm spatial resolution, and (2) downstream of NRP discharges in air and in plasma-assisted methane/air flames, using multi pass cell. [...]
Maisons, Grégory. "Réalisation de source lasers monomodes innovantes émettant dans le moyen infrarouge : application à la spectroscopie". Phd thesis, Grenoble, 2010. http://www.theses.fr/2010GRENY058.
This thesis work is focused on the top metal grating applied to the Quantum Cascade Lasers operating in the mid-infrared range of the electromagnetic spectrum. Physic phenomena involved in such structure have been understood thank to simple models which have been powerful tools to design devices. Results are confirmed by numerical studies based on the more complex S-matrix formalism. This study leads to several realizations: (i) The processing of single-mode sources with a precise control of the wavelength. The originality of these devices comes from the low loss interaction of the electromagnetic field with the metal. This configuration enables the processing of room temperature continuous wave distributed feedback (DFB) QCLs. (ii) The development of low divergence new devices, based on the combining of a first-order and a second order grating. (iii) The demonstration of the capability of a QCL optically coupled to a high finesse cavity (OF-CEAS : Optical-Feedback Cavity-Enhanced Absorption Spectroscopy) for the high sensitive molecular spectroscopy. All these developments have demonstrated the high maturity level of the top metallic grating, well adapted to the quantum cascade laser for their integration in spectroscopic systems
Wang, Feihu. "Ultrafast terahertz pulse generation from quantum cascade lasers". Electronic Thesis or Diss., Paris 6, 2016. http://www.theses.fr/2016PA066752.
THz quantum cascade lasers (QCLs) are foundational semiconductor devices for laser action in the THz range. Considerable developments have been made in the last decade in terms of temperature operation and high output power. THz QCLs can also possess extremely large spectral bandwidths, rendering them suitable for ultrashort THz pulse generation through modelocking, with pulse widths of a few picoseconds theoretically obtainable. However, to date, the generation of THz pulses from QCLs has been limited to 10 - 20 ps, despite several years of research effort. In this thesis, this bottleneck in QCL technology is investigated and overcome. Several milestones have been achieved that permitted the realization of ultrashort pulse generation from QCLs. Current state-of-the-art performances are shown, using narrow spectral bandwidth QCLs in single-plasmon waveguides, and where modelocking results in 20 ps long THz pulses at low temperatures (10K). This is followed by, for the first time, mode-locking of broad spectral bandwidth QCLs in sub-wavelength metal-metal waveguides at ‘high’ temperatures (77K). Even with large spectral bandwidths, the shortest pulses achieved were only 11 ps and we show that the index dispersion and the electrical modulation are the critical factors. Finally, these effects are compensated through a Gires-Tournois interferometer and an extra loss mechanism, respectively, integrated monolithically onto a QCL. This approach permits to generate pulses as short as 4 ps, with the potential to go considerably further to the sub-picosecond or single cycle regime
Abadie, Claire. "Détecteurs et lasers THz à base d'antennes accordables en fréquence". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS145/document.
Optoelectronic devices are crucial for many applications in everyday life: computers, smartphones, connected objects in general.The THz range (0.1-10 THz) still remains industrially unexploited because of the intrinsic difficulties to produce or generate THz photons. However, many applications exist for THz radiation : in the medical field for example, for the sensitive detection of gases, or for the imaging of concealed objects in the visible range.This thesis focuses on quantum well photodetectors (QWIPs) and quantum cascade lasers (QCLs) operating in the THz range in order to develop compact, fast and sensitive devices (but operating at cryogenic temperatures).We used Split Ring Resonators (SRR), inspired by metamaterial research, in order to design and develop subwavelength tunable THz detectors with an external inductance.Concerning lasers, this thesis studies THz micro-lasers using microdisk resonators with the aim of designing and manufacturing lasers operating on the fundamental electromagnetic mode (dipolar mode). The future perspective of this work is to build an entirely sub-wavelength and fast laser in the THz spectral range
Nguyen, Van Hoang. "Transistor Quantique InAs à Electrons Chauds : Fabrication submicronique et étude à haute fréquence". Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20084/document.
This work aims to develop a new high speed transistor in a vertical transport configuration that exploits the favourable transport properties of III-V semiconductor heterostructures based on InAs. This transistor is similar to a heterojunction bipolar transistor (HBT), but has theoretical assets to overcome the fundamental high speed limits of electron transport in HBT. Our approach uses the concept of hot electron transistor in an original InAs/AlSb quantum heterostructure, that we called a quantum hot electron transistor (QHET) or quantum cascade transistor (QCT). This research was almost done in Southern Electronics Institute (IES) under supervision of Dr. Roland Teissier and other work was realized in Micro-Nanotechnology Electronics Institute (IEMN) under supervision of Dr. Mohamed Zaknoune. The QHET is a unipolar vertical transport device made of a InAs/AlSb quantum heterostructure. Its first advantage over npn HBTs is the low base sheet resistance of 250 Ω/□ , accessible with moderate n-type doping levels (typically 1018 cm-3), which is a key parameter for high speed operation. Secondly, electron transport in the short (typically 100nm) bulk InAs collector is mostly ballistic with calculated transit times much shorter than in InP-based devices. We already developed the design and technology of QHET and demonstrated its resonant transports at cryogenic temperature and its improved static operation in smaller device. From these results, we come to develop our QHET structures to achieve high current gain. Using quantum design of thin base, the current gain is about 15. We fabricated QHET with emitter width scaled down to 0.3µm, using a state of the art electron beam lithography process. The junctions are defined using selective chemical etching. The base contact is self-aligned on the emitter contact. We achieved base resistance lower than 50Ω, comparable to state of the art HBTs. The small dimension allowed reaching the high current density regime of up to 1 MA/cm² required for high frequency operation. The static current gain is about 10, but could be increased up to 14 using a new quantum design. The collector breakdown voltage is greater than 1.2 V.Towards high frequency measurement, the substrate must be non-conducting material but InAs substrate is not available. Two technologies were proposed: transferred substrate and metamorphic substrate. For transferred substrate technology, we obtained a response of cutoff frequency of 77 GHz for FT and 88 for FMAX. For metamorphic substrate technology, we performed the growth of the transistor structures on a semi-insulating GaAs substrate. We used a thin GaSb buffer layer for metamorphic growth of the active part of the transistor, with an adequate growth procedure that allows forming mainly 90° misfit dislocations at the interface between the GaAs and GaSb. This technique permits more convenient and reliable processing of the devices, as compared to use of the more standard AlSb thick buffer layer. The frequency response was determined from S-parameters measured with a network analyser up to a frequency of 70 GHz. The measured gains, after de-embedding of the connection parasitic for a device with 0.5x4µm² emitter for JC=350kA/cm² (Ic= 6.0mA, Ib= 0.7mA, Vce=1.3V). The frequency dependence is not conventional on this device, with a resonance in the current gain close to 10 GHz and a slope different from -20 dB/decade for Mason's unilateral gains. Nevertheless, we could extract the cut-off frequencies FT=172 GHz from H21 and FMAX =230 GHz using -20dB/decade extrapolation of maximum stable gain (MSG). The present results confirmed the validity of this novel device concept. In addition, this is the first demonstration of the ability of a hot electron transistor to operate at high frequency at room temperature
Shen, Fengjiao. "Development of a laser heterodyne radiometer for atmospheric remote sensing". Thesis, Littoral, 2019. http://www.theses.fr/2019DUNK0542.
The measurement of vertical concentration profiles of atmospheric trace gases provides a better insight into air pollution, ozone destruction and climate change as well as a way to validate chemical models and satellite observations. To that end, laser heterodyne radiometer (LHR) offers significant benefits in terms of high spectral resolution, high sensitivity and high vertical resolution in conjunction with a compact instrumental size deployable for field applications. The aim of this thesis is to develop a fully transportable mid-infrared (mid-IR) LHR instrument for ground-based remote sensing of key trace gases in the atmospheric column. In order to test our design and characterize its performance, a proof of concept (PoC) mid-IR LHR receiver was first developed. Its field test was carried out on the QualAir platform of the University Pierre et Marie Curie (UPMC) with the help of a heliostat of the TCCON-Paris station (TCCON : Total Carbon Column Observing Network). LHR absorption spectrum of CH₄ in the atmospheric column was extracted from the solar radiation using the developed ground-based LHR receiver and it is good agreement with the spectrum measured by the TCCON-Paris station. After this field test validation, a fully transportable mid-IR LHR instrument was developed and deployed on the roof of the IRENE platform of the University of Littoral-Côte d'Opale (ULCO) in Dunkirk. LHR spectrum of CH₄ and N₂O in the atmospheric column was measured and in good agreement with the TCCON FT-IR spectrum of CH₄ and N₂O, as well as in good agreement with the atmospheric transmission modelling. The fully transportable mid-IR LHR instrument developed in this PhD work has high potential use in measurement of vertical concentration profiles of key atmospheric species on spacecraft, on airbone or on ground-based platform
Boulley, Laurent. "Développement de dispositifs à base de dioxyde de vanadium VO ₂ et de méta-surfaces dans le moyen infrarouge : applications passives et intégration sur des lasers à cascade quantique". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS150.
The thesis work presented in this manuscript deals with the development of vanadium dioxide VO₂ and meta-surfaces based devices in the mid-infrared for passive applications and an integration on quantum cascade lasers (QCL).This work enabled the elaboration of new deposition conditions for the VO₂ phase change material by pulsed laser ablation at temperatures compatible with III-V heterostructures used in optoelectronics. The characterizations of the VO₂ coated thin films show a change in reflectivity and in electric conductivity between the insulating state at low temperature and the metallic state at high temperature around 68°C (341 K).Developments were then carried out on the use of a meta-surfaces array in order to obtain an homogeneous layer of resonant effective refractive index. These meta-surfaces are constituted by split-ring resonators, whose resonance frequency can be adjusted by choosing their geometric parameters and the materials they are made of. An optical modulation of more than 100cm-1 of the resonance peak has been obtained during the phase transition with meta-surfaces deposited on a VO₂ layer. This result is very promising for the conception of monolithic, robust, compact, frequency tunable devices and whose optical properties only depend on the VO₂ layer temperature.Finally, this work studies the functionalization of mid-infrared QCL (7-8 µm) with VO₂ and meta-surfaces layers. It aims at understanding the influence of the integrated layers on the emission properties. In order to ensure a good interaction between these layers and the laser guided mode while having low optical losses, new waveguides were modeled, then the first VO₂ based QCL have been demonstrated and a maximum operating temperature of 334 K has been measured
Pistore, Valentino. "Modelocking of THz quantum cascade lasers : dispersion control and non-linearities". Electronic Thesis or Diss., Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2019SORUS302.pdf.
THz QCLs are nowadays considered a promising platform for the generation of intense and ultrashort THz pulses. Owing to their fast gain recovery time, passive modelocking of THz QCLs has so far proved to be difficult. On the contrary, active modelocking with a microwave modulation has been successfully applied. The pulse duration, however, has been arduous to reduce despite years of research. In 2017, THz pulses as short as 4ps have been generated by our group with the application of an integrated structure (a GTI) aiming to reduce the chromatic dispersion. The research in this thesis starts from this point.In particular, I present dispersion engineering in THz QCLs in order to obtain very short pulses even from relatively narrow-band devices. This is achieved using proven active modulation methods that can tune the QCL emission from high to low dispersion regimes. I also show that THz QCLs can present a strong amplitude modulation of their emission profile and that they can spontaneously emit pulses as a result of a self-locking mechanism, contrary to the expected frequency modulated response. As a consequence, this indicates that the fast gain recovery time is not a limiting factor for the generation of pulses. I also show this passive self-locking scheme for passive pulse generation in the framework of the first demonstrations of harmonic modelocking of THz QCLs. Finally, a new phenomenon is presented where the modes of a free running THz QCL can beat together to generate free space microwave emission
Bielsa, Franck. "Spectroscopie vibrationnelle à deux photons de l'ion H2+ : développement d'une source laser à 9.166 microns". Paris 6, 2007. https://tel.archives-ouvertes.fr/tel-00199877.
Abajyan, Pavel. "Génération et contrôle de peignes de fréquences optiques dans les lasers à cascade d'interbande (ICL)". Electronic Thesis or Diss., Sorbonne université, 2024. http://www.theses.fr/2024SORUS024.
Optical frequency combs (OFCs) are coherent light sources that emit a broad spectrum of discrete, perfectly spaced modes, each with an absolute frequency measurable with the precision of an atomic clock.OFCs in the mid-infrared (MIR 3-12 μm) have recently become of great interest to molecular spectroscopy by the presence of strong absorption of molecular vibration and rotation modes in the spectroscopic "fingerprint" region. Nevertheless, the operation of the OFC in the crucial mid-infrared region (MWIR 3-6 μm) remains significantly underdeveloped compared to other parts of the MIR.In this work, we present an in-depth experimental study of a new generation of interband cascade laser (ICL) and their potential for OFCs in MWIR. The thesis provides proof of the OFC regime both by high-frequency beatnote spectroscopy (BN), and by the new technique of temporal reconstruction of the ultrafast dynamics of these lasers, this making it possible to "visualize" the control of the type of operation of the OFC in ICL. In particular, was carried out the optoelectrical characterization of a set of ICLs with a range of geometries, with the aim of studying low group delay dispersion (GDD) ICLs at longer wavelengths than those previously studied: an ICL operating at 3.8 μm with a 2-section architecture, ICLs operating at 4.1 μm, and another generation of ICL operating at a wavelength of 4.2 μm designed with a wide spectral gain. OFC regime formation and GDD are linked and important for understanding the fundamental mechanisms of OFC formation. ICLs were studied using optical and electrical BN spectroscopy. Passive mode locking (PML) (or free running) and active mode locking (AML) were demonstrated. For 2-section ICLs, where the ICL is divided into a long part and a short part for a single cavity, the exact effect of the small section on the BN has been explained: allows to (a) control very finely the intracavity GDD, (b) introducing losses and showing that we converge towards PML behavior.This work then feeds into the case of ICLs operating at longer wavelengths in a single section cavity and where the GDD is expected to be less. In the particular case of the ICLs operating at 4.1 μm, we demonstrate a strong optical BN, which can be injection locked by radio frequency (RF) injection at the round trip frequency of the ICL, showing the first-steps of active modelocking. This injection locking was achieved using a simple single-section laser architecture with very low waveguide dispersion, and showing that adapting the ICL waveguide for RF operation is not a fundamental requirement. In the final part of the thesis, we show the implementation of the "Shifted Wave Interference Fourier Transform Spectroscopy" (SWIFTS) technique, used in two different configurations, to reconstruct the laser's temporal intensity profile at ultrafast timescales. This permits to demonstrate the nature of OFC generated in these ICLs. Indeed, we show that the ICL operates in the frequency modulation (FM) regime when free-running and transits towards an amplitude modulation (AM) regime when actively modelocked. Interestingly, we also show that ICLs can generate short pulses of ~6.7 ps in free-running operation, despite FM operation, and highlight the control of the pulse width and peak intensity via RF injection. This permits to compress the free-running pulses by a factor of 2.3 to obtain sub-3 ps pulses.This work constitutes an important step in the creation and control of OFCs in the MWIR region. The prospects are to broaden the spectral bandwidth of ICLs and generate high-power ultrashort pulses in the MWIR and beyond
Lemoine, Paul-Arthur. "Etudes de l'émission thermique et de lasers à cascade quantique dans l'infrarouge par microscopie optique en champ proche à pointe diffusante". Châtenay-Malabry, Ecole centrale de Paris, 2008. http://www.theses.fr/2008ECAP1089.
We present a novel setup based on apertureless near-field scanning optical microscopy (ANSOM) designed for detecting infrared thermal radiation at the surface of a photonic structure with a resolution far beyond the diffraction limit which is close to 5µm in the infrared frequencies). This new instrument is a powerful means to obtain optical information with a resolution equal to 100nm. The system is based on a home-made ANSOM. It is an atomic force microscope (AFM) combined with infrared optics. The AFM uses a tungsten tip in tapping mode to provide a topographic image of the sample and to scatter evanescent waves. As the sample is heated by a hot plate, temperature excites thermal radiation from the surface, which is scattered by the AFM tip in the near-field. Light scattered by the tip is then collected and focused on an infrared detector, producing a near field infrared thermal image. We performed observations on gold geometric patterns deposited on a SiC substrate. The sample is heated up to 180°C. We imaged interferences of gold plasmons and demonstrated the first direct experimental proof of the spatial coherence of thermal radiation in near field. We also realized study of the surface of an quantum cascade laser. These devices present an evanescent field at their top surface proportional to the field present inside the cavity. By scattering this evanescent field, our system gives access to the Fabry-Perot interference fringes inside the laser cavity
Zhao, Zhenyu. "Spectroscopie térahertz ultrarapide et propriétés optiques non-linéaires de nanostructures semiconductrices". Paris 6, 2008. http://www.theses.fr/2008PA066264.
Bielsa, Franck. "Spectroscopie vibrationnelle à deux photons de l'ion H2+: développement d'une source laser à 9,166µm". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2007. http://tel.archives-ouvertes.fr/tel-00199877.
Tran, Dang Bao An. "Widely tunable and SI-traceable frequency-comb-stabilised mid-infrared quantum cascade laser : application to high precision spectroscopic measurements of polyatomic molecules". Thesis, Sorbonne Paris Cité, 2019. http://www.theses.fr/2019USPCD060.
The thesis consists in developing a high-resolution mid-infrared spectrometer traceable to primary frequency standards and providing a unique combination of resolution, tunability, detection sensitivity and frequency control. A quantum cascade laser (QCL) emitting at 10.3 µm is phase locked to an optical frequency comb stabilized to a remote 1.55 µm ultra-stable reference developed at LNE-SYRTE, monitored against primary frequency standards and transferred to LPL via an active noise compensated fibre link. This results in a 0.1 Hz QCL linewidth, a stability below 10⁻¹⁵ at 1 s and an uncertainty on its absolute frequency below 4 × 10⁻¹⁴. Moreover, the setup allows the QCL to be widely scanned over 1.4 GHz while maintaining the highest stabilities and precision. This QCL was used to carry out saturated absorption spectroscopy of several molecules in a compact multipass cell. We demonstrated statistical uncertaintyon line-center frequencies at the kHz level and sub-10 kHz systematic uncertainty. We have recorded several singular K-doublets and many rovibrational transitions of methanol, in particular weak transitions and weak doublets - unreported so far. Precise parameters modelling trioxaneh ave been determined with only a few tens of rovibrational transitions recorded at unprecedented accuracy. The quadrupole hyperfine structure of an ammonia transition has been resolved for thefirst time. This setup constitutes a key element for the project aiming at the first observation of parity violation in molecules currently held at LPL, and, more generally, for various fields of physics, from atmospheric and interstellar physics to fundamental physics beyond the standard model
Bloom, Guillaume. "Combinaison cohérente de lasers à cascade quantique". Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00678958.
Becker, Cyrille. "Lasers à cascade quantique : étude physique et ingénierie de la structure quantique". Palaiseau, Ecole polytechnique, 2002. http://www.theses.fr/2002EPXX0040.
Karr, Jean-Philippe. "Optique quantique dans les microcavités semi-conductrices. Spectroscopie de l'ion moléculaire H2+". Habilitation à diriger des recherches, Université d'Evry-Val d'Essonne, 2008. http://tel.archives-ouvertes.fr/tel-00347825.
J'aborde dans la deuxième partie mes activités théorique et expérimentale autour de la spectroscopie de l'ion H2+. Le but de l'expérience, qui a débuté en 2003 à l'université d'Evry, est de mesurer la fréquence d'une transition vibrationnelle à deux photons sans effet Doppler, et de la comparer à des prédictions théoriques précises pour en déduire une nouvelle détermination du rapport mp/me. Je décris les progrès des calculs de haute précision sur l'ion H2+ (niveaux d'énergie non relativistes, structure hyperfine), ainsi que le dispositif expérimental mis en place et les perspectives de l'expérience.
Zhao, Zhen-Yu. "Spectroscopie Térahertz Ultrarapide et Propriétés Optiques Non-Linéaires de Nanostructures Semiconductrices". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://tel.archives-ouvertes.fr/tel-00300727.
1. Le développement de la spectroscopie Térahertz dans le domaine temporel (THz-TDS) et son utilisation pour mesurer le gain d'un laser à cascade quantique GaAs/AlGaAs.
2. L'étude des effets de 3ième ordre en optique non linéaire dans des verres de Tellure dopés en nanocristaux AgCl, par "Z-scan" et mélange à quatre ondes (DFWM).
A cette fin, nous avons d'abord construit un montage de spectroscopie Térahertz dans le domaine temporel avec deux sources de rayonnement différentes : la rectification optique dans un cristal non-lineaire <110> ZnTe et par ailleurs des antennes interdigités photoconductrices.
Dans un premier temps, nous avons étudié la compétition entre la rectification optique, la génération de second harmonique, l'absorption à deux photons, et l'absorption par les porteurs libres. Le faisceau pompe subit une absorption à deux photons et le rayonnement THz émis est diminué, dans les conditions de focalisation, par l'absorption des porteurs libres. La réduction de l'émission THz dans les conditions de focalisation est expliquée, à condition de tenir compte des effets de la diffraction de la source THz sub-longueur d'onde.
Dans un deuxième temps, nous avons étudié les propriétés de l'émission THz dans le domaine temporel et spectral d'un nouveau type d'antenne photoconductive interdigitée basée sur du GaAs semi-isolant, en fonction de la densité de porteurs et dans une gamme de température allant de 4.2K à 270K. Les propriétés de l'émission THz sont linéaires pour de faibles tensions appliquées mais révèlent des effets de saturation pour des tensions importantes en raison de la diffusion inter-vallées de la bande Γ à la bande L. Les performances THz saturent aussi pour de fortes excitations laser à raison de l'écrantage des charges. La dynamique des porteurs à été étudiée expérimentalement pour différentes températures. Le spectre THz de l'émission se déplace vers les basses fréquences lorsque la température augmente. L'influence de la mobilité électronique est discutée.
Dans une troisième partie, après avoir comparé les deux méthodes de génération THz ci-dessus et décidé d'utiliser les antennes photoconductives comme source d'excitation pour notre montage THz-TDS, nous avons étudié le gain et les pertes d'un laser à cascade quantique (LCQ) fonctionnant à 2.9 THz. Nous avons étudié les variations du gain en fonction du courant injecté, à différentes températures. Nous avons mesuré les spectres d'amplitude et de phase THz, permettant une détermination directe du gain. A la fréquence de fonctionnement du LCQ, nous mesurons un gain de 6.5cm-1. Des effets comme le « clampage » du gain et l'affinement spectral du gain sont observés et discutés.
Pour finir, nous avons étudié le coefficient de polarisabilité d'ordre 3 des verres de Tellure (80TeO2-20Nb2O5) dopés en nanocristaux AgCl. Nous avons produit des échantillons par les techniques fonte-trempe et traitement thermique. Les résultats de la caractérisation révèlent qu'un traitement plus long augmente la tailles des nanocristaux qui donne lieu à l'apparition de plus de défauts et une plus grande déformation du réseau cristallin des nanocristaux aux interfaces avec le verre. Des états électroniques piégés apparaissent sous l'effet de la déformation de la structure cristalline. Une forte absorption à deux photons et une absorption des états électroniques piégés réduit le seuil de la limitation optique. Le coefficient polarisabilité non linéaire χ(3) augmente à cause de la formation des défauts et des états électronique localisés.
Leuliet, Aude. "Simulation du transport dans les lasers à cascade quantique". Paris 7, 2010. http://www.theses.fr/2010PA077070.
Quantum cascade lasers (QCLs) are unipolar semiconductor devices based on the electronic transitions in the conduction band of a multiple quantum wells Systems and on resonant tunnelling. They are the only coherent semiconducting sources in the mid infrared to allow ambient temperature operation. The thesis aims at calculating the current in QCLs. After a short introduction on QCLs, the thesis is divided into 3 parts. The first part details the different diffusion processes taking place in the active region and determines which are the most important processes. The second part contains a study of QCLs under strong magnetic fields (up to 45 Teslas). This allow a more precise determination of processes taking place in the active region. The last part describes the calculation of the current in the QCL, based on the diffusion determined in the first chapters
Naurois, Guy-Maël de. "Combinaison monolithique de lasers à cascade quantique par couplage évanescent". Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112423/document.
During the last 10 years, the quantum cascade lasers performances in the mid-infrared have been considerably improved: the wall plug efficiency has reached values superior to 20%, with output power up to 5W in continuous wave operation, at room temperature. Those values have been achieved due to the reduction of the temperature sensibility of the lasers, with characteristic temperature T0 reaching 300K. The output power is now limited to the injected power, which is proportional to the gain region size. This thesis reports an innovating solution consisting on beam combining an array of narrow emitters, monolithically. We experimentally demonstrate for the first time devices of up to 32 emitters of 2µm width emitting in phase by evanescent coupling. Moreover, we show record thermal resistance. Those results highlight the possibility to fabricate high power sources (superior to 10 W) in the mid-infrared, with a good beam quality
Bahriz, Michaël. "Lasers à cascade quantique et leurs applications aux cristaux photoniques". Phd thesis, Université Paris Sud - Paris XI, 2008. http://tel.archives-ouvertes.fr/tel-00285503.
De, Naurois Guy-Maël. "Combinaison monolithique de lasers à cascade quantique par couplage évanescent". Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00829111.
Houver, Sarah. "Optique non-linéaire résonante dans les lasers à cascade quantique". Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066046/document.
Quantum cascade lasers (QCLs) are powerful terahertz (THz) and mid-infrared (MIR) sources. Their emission relies on intersubband transitions i.e. transitions between confined electronic states in the conduction band of these semiconductor nanostructure-based lasers.This PhD thesis presents a fundamental study of resonant nonlinear optics in QCLs. Nonlinear frequency mixing between a THz or MIR QCL photon and a near infrared (NIR) pump has been shown within the QCL cavity. Nonlinearities from the QCL active region, composed of a set of quantum wells, can be enhanced owing to a NIR excitation that is resonance with interband transitions, and with the QCL photon in resonance with intersubband transitions. These resonant excitations permit a strong exaltation of the nonlinear susceptibility, allowing an efficient interaction without considerations of phase matching. Previous studies, limited to cryogenic temperatures, have shown nonlinear frequency mixing between a GaAs based THz QCL and an 800 nm NIR beam.This thesis presents an original work highlighting that resonant nonlinear optics in QCLs can be extended to the MIR, and to telecom range pump excitations, at room temperature. Furthermore, previously limits related to absorption at resonant excitations have also been partially overcome, by proposing a geometry in reflection.As well as proving an in-depth understanding of interband and intersubband nonlinearities in QCLs, this work paves the way to potential applications such as all optical wavelength shifting for telecommunications, and the up-conversion of THz and MIR photons into thetechnologically mature NIR range
Houver, Sarah. "Optique non-linéaire résonante dans les lasers à cascade quantique". Electronic Thesis or Diss., Paris 6, 2017. http://www.theses.fr/2017PA066046.
Quantum cascade lasers (QCLs) are powerful terahertz (THz) and mid-infrared (MIR) sources. Their emission relies on intersubband transitions i.e. transitions between confined electronic states in the conduction band of these semiconductor nanostructure-based lasers.This PhD thesis presents a fundamental study of resonant nonlinear optics in QCLs. Nonlinear frequency mixing between a THz or MIR QCL photon and a near infrared (NIR) pump has been shown within the QCL cavity. Nonlinearities from the QCL active region, composed of a set of quantum wells, can be enhanced owing to a NIR excitation that is resonance with interband transitions, and with the QCL photon in resonance with intersubband transitions. These resonant excitations permit a strong exaltation of the nonlinear susceptibility, allowing an efficient interaction without considerations of phase matching. Previous studies, limited to cryogenic temperatures, have shown nonlinear frequency mixing between a GaAs based THz QCL and an 800 nm NIR beam.This thesis presents an original work highlighting that resonant nonlinear optics in QCLs can be extended to the MIR, and to telecom range pump excitations, at room temperature. Furthermore, previously limits related to absorption at resonant excitations have also been partially overcome, by proposing a geometry in reflection.As well as proving an in-depth understanding of interband and intersubband nonlinearities in QCLs, this work paves the way to potential applications such as all optical wavelength shifting for telecommunications, and the up-conversion of THz and MIR photons into thetechnologically mature NIR range