Добірка наукової літератури з теми "Polarization photodetectors"

AbstractThis article reviews the optical polarization properties of unstrained and strained GaN films with a nonpolar orientation. In unstrained a -plane GaN films, the A exciton becomes completely linearly polarized perpendicular to the c-axis, whereas the B and C excitons are only partially polarized. In m -plane or a -plane GaN films under anisotropic in-plane compressive strain, all three interband transitions between the three uppermost valence bands and the conduction band can become linearly polarized for sufficiently large strain values. The complete linear polarization can be directly observed in reflection, transmission, or photoreflectance by a polarization-dependent energy gap. This complete linear polarization can be used to realize polarization-sensitive photodetectors in the ultraviolet spectral range, which do not need a polarization filter in front of the photodetector. By combining a polarization filter and photodetector or two photodetectors from the same material with their c-axes oriented perpendicular to each other, a narrowband photodetection configuration can be achieved in the ultraviolet spectral range with a band width below 8 nm. Since both realizations are also polarization sensitive, a configuration with four photodetectors is necessary to achieve narrow-band sensitivity regardless of the polarization state of the incident light. At the same time, the configuration with four photodetectors allows for the determination of the absolute angle of polarization.

Single silicon nanowire-based MSM photodetectors show ultra high responsivity (>10⁴ A W⁻¹) in the near-infra-red region, even at zero bias. The observed photoresponse is sensitive to the polarization of the exciting light, allowing the device to act as a polarization-dependent photodetector.

We report a GaN based metal–semiconductor–metal (MSM) infrared photodetector enabled with azimuthally distributed sub-wavelength gratings fabricated on one of the working electrodes. Under illumination, hot electron transfer is introduced by the plasmonic resonance in the infrared waveband formed at the interface of Au/GaN. Without the help of using any external optical polarizers, the device is able to detect radial polarization vortices in the form of photocurrents with a prescribed response spectrum. The detector exhibits a 10%–90% rise and fall time of 0.9 ms under modulated light, much faster than that of conventional ultraviolet GaN MSM photodetectors based on the band edge absorption. This work provides a viable way to measure spatially variant polarization beams with a compact plasmonic photodetectors fabricated from wide bandgap semiconductors.

Photodetectors are the essential building blocks of a wide range of optical systems. Typical photodetectors only convert the intensity of light electrical output signals, leaving other electromagnetic parameters, such as the frequencies, phases, and polarization states unresolved. Metasurfaces are arrays of subwavelength structures that can manipulate the amplitude, phase, frequency, and polarization state of light. When combined with photodetectors, metasurfaces can enhance the light-matter interaction at the pixel level and also enable the detector pixels to resolve more electromagnetic parameters. In this paper, we review recent research efforts in merging metasurfaces with photodetectors towards improved detection performances and advanced detection schemes. The impacts of merging metasurfaces with photodetectors, on the architecture of optical systems, and potential applications are also discussed.

Abstract Tin sulfide semiconductor nanowires (NWs) have been widely investigated for photodetection applications because of their good optical and electrical properties. Herein, we synthesized n-type SnS2 NWs and then fabricated SnS2 NW photodetectors with a ferroelectric polymer side-gate. The strong electric field induced by ferroelectric polymer can effectively suppress the dark current and improve the detectivity in SnS2 NW photodetectors. The photodetectors after polarization depletion exhibit a high photoconductive gain of 4.0 × 105 and a high responsivity of 2.1 × 105 A W−1. Compared with devices without polarization depletion, the detectivity of polarization-depleted photodetectors is improved by at least two orders of magnitude, and the highest detectivity is 1.3 × 1016 Jones. Further, the rise and fall time are 56 and 91 ms respectively, which are about tens of times faster than those without polarization depletion. The device also shows a good spectral response from ultraviolet to near-infrared. This study demonstrates that ferroelectric materials can enhance optoelectronic properties of low-dimensional semiconductors for high-performance photodetectors.

Abstract The in-plane anisotropy of transition metal trichalcogenides (MX3) has a significant impact on the molding of materials and MX3 is a perfect choice for polarized photodetectors. In this study, the crystal structure, optical and optoelectronic anisotropy of one kind of quasi-one-dimensional (1D) semiconductors, ZrSe3, are systematically investigated through experiments and theoretical studies. The ZrSe3-based photodetector shows impressive wide spectral response from ultraviolet (UV) to near infrared (NIR) and exhibits great optoelectrical properties with photoresponsivity of 11.9 mA·W-1 and detectivity of ~106 at 532 nm. Moreover, the dichroic ratio of ZrSe3-based polarized photodetector is around 1.1 at 808 nm. This study suggests that ZrSe3 has potential in optoelectronic applications and polarization detectors.

AbstractThe integration of quantum well infrared photodetectors with plasmonic cavities has allowed for demonstration of sensitive photodetectors in the mid-infrared up to room-temperature operating conditions. However, clear guidelines for optimizing device structure for these detectors have not been developed. Using simple stripe cavity detectors as a model system, we clarify the fundamental factors that improve photodetector performance. By etching semiconductor material between the stripes, the cavity resonance wavelength was expected to blue-shift, and the electric field was predicted to strongly increase, resulting in higher responsivity than unetched stripe detectors. Contrary to our predictions, etched stripe detectors showed lower responsivities, indicating surface effects at the sidewalls and reduced absorption. Nevertheless, etching led to higher detectivity due to significantly reduced detector dark current. These results suggest that etched structures are the superior photodetector design, and that appropriate sidewall surface treatments could further improve device performance. Finally, through polarization and incidence angle dependence measurements of the stripe detectors, we clarify how the design of previously demonstrated wired patch antennas led to improved device performance. These results are widely applicable for cavity designs over a broad range of wavelengths within the infrared, and can serve as a roadmap for improving next-generation infrared photodetectors.

Self-powered photodetectors have the advantages of high sensitivity, sustainability, and small size and have become a research hotspot in advanced optoelectronic systems. However, the low output photocurrent density seriously hinders the practical application of ferroelectric self-powered photodetectors. Herein, the high-efficiency photoelectric detection performance of the Bi1-xHoxFeO3 ferroelectric self-powered photodetector is realized by doping Ho. The responsivity (R) and detectivity (D*) can reach 0.0159 A/W and 1.94 × 1011 Jones under monochromatic light with a wavelength of 900 nm. Meanwhile, the R and D* can reach 0.022 A/W and 2.65 × 1011 Jones under sunlight. These excellent photodetection performances are attributed to the high short-circuit current density (Jsc). When the Ho content is 6%, the output photocurrent reaches up to 0.81 mA/cm2. The systematic structure and photo-electric characteristic analysis suggest that the decrease in the band gap leads to the generation of a larger photocurrent while the ferroelectric polarization is reduced slightly. This work provides a new way to obtain high-performance self-powered photodetectors.

Photodetectors are a kind of semiconductor devices that convert incoming light to an electrical signal. Photodetectors are classified based on their different structure, fabrication technology, applications and different sensitivity. Infrared photodetectors are widely used in many applications such as night vision, thermal cameras, remote temperature sensing, and medical diagnosis etc.   All detectors have material inside that is sensitive to incoming light. It will absorb the photons and, if the incoming photons have enough energy, electrons will be excited to higher energy levels and if these electrons are free to move, under the effect of an external electric field, a photocurrent is generated.   In this project Fourier Transform Infrared (FT-IR) Spectroscopy is used to investigate a new kind of photodiodes that are based on self-assembled semiconductor nanowires (NWs) which are grown directly on the substrate without any epi-layer. The spectrally resolved photocurrent (at different applied biases) and IV curves (in darkness and illumination) for different temperatures have been studied respectively. Polarization effects (at low and high Temperatures) have been investigated.  The experiments are conducted for different samples with high concentration of NWs as well as with lower concentration of NWs in the temperature range from 78 K (-195ºC) to 300 (27ºC). These photodiodes are designed to work in near infrared (NIR) spectral range.   The results show that the NW photodetectors indeed are promising devices with fairly high break down voltage, change of photocurrent spectra with polarized light, low and constant reverse saturation current (Is). The impact of different polarized light on photocurrent spectra has been investigated and an attempt has been made to clarify the observed double peak of InP photocurrent spectrum. Our investigations also include a comparison to a conventional planar InP p-i-n photodetector.

This thesis deals with the precise measurement of distances in nanometer range at ultrasonic frequencies for the purposes of vibrometry. The paper is primary focused on~nanometric displacement measurement methods. First the thesis deals with the physical phenomena based on light in the theoretical section. This includes interference of light, index of refraction, polarization, interferometry and more. Understanding of these physical laws is crucial for design and assembling of the interferometer. Subjects of interferometric method for precise and fast measurement of the nanometric displacement and vibration are discussed. Interferometer components such as lasers, photodetectors and optical elements are described are described in the final part of this section. Practical section of thesis can be divided into two parts. The design and assembling issues are discussed in the first section. Many problems which I had to solve are described. Control software and implementation of the signal processing is the subject of the second part. I met with particular problems such as phase unwrapping. I solved this problem of discontinuous phase field with user written algorithm. Finally the graphical user interface was created. Using assembled interferometer and written software application I measured vibration of Langevin transducer on ultrasonic frequencies.

Les semi-conducteurs bidimensionnels possèdent de nombreuses propriétés fonctionnelles intéressantes telles qu’électriques, optiques, magnétiques, thermiques etc., qui permettent des applications potentielles notamment dans les dispositifs optoélectroniques ultraminces, transparents et hautement intégrés. La synthèse de nouveaux matériaux bidimensionnels et l’exploration de leurs performances optimales, ainsi que le développement de leurs applications font l’objet d’une intense activité de recherche dans le domaine des matériaux. Cette thèse s’inscrit dans la recherche de nouveaux matériaux bidimensionnels. Un premier axe vise à injecter un courant polarisé en spin dans une structure semi-conductrice bidimensionnelle à base de MoS₂ en vue de contrôler la polarisation de l’émission optique. L’objectif est ici d’élaborer une couche ferromagnétique de CoFeB à aimantation perpendiculaire capable d’injecter des électrons polarisés sans champ magnétique, et sur une grande surface. L’obtention de tels émetteurs optique polarisés doit s’accompagner du développement de photodétecteurs de lumière polarisée à base de matériaux bidimensionnels. C’est l’objet des deux autres axes de cette thèse dans lesquels la photo-détection basée sur les nouveaux semi-conducteur GeAs et des alliages d’éléments des groupes IV-VI tels que SnS et ZnSnS est étudiée. Concernant l’injecteur de spin, on s’intéresse à la fabrication des structures Ta/CoFeB/MgO ayant une large anisotropie magnétique perpendiculairement à l’axe de croissance. Un point important est la réalisation d’un dépôt homogène couvrant toute la surface de la monocouche de MoS₂ sous-jacente, constituant l’émetteur de lumière. En optimisant l’épaisseur de la couche de CoFeB et la température du recuit, on obtient une grande énergie d’anisotropie magnétique perpendiculaire valant 0.975 mJ/m². Par l’analyse des propriétés structurales et chimiques de l’hétérostructure, il est montré que l’insertion de MgO entre le métal ferromagnétique et le matériau bidimensionnel peut efficacement bloquer la diffusion des atomes du ferromagnétique. Il est également montré que la couche de Ta joue un rôle critique « d’absorption » des atomes de B de la couche de CoFeB ce qui induit l’aimantation perpendiculaire. D’après les calculs ab initio, l’épaisseur de MgO peut être ajustée pour modifier la structure de bande de MoS₂, allant d’un gap indirect avec pour une couche de MgO de 7 monocouches (MCs) à un gap direct pour une couche de MgO de 3 MCs. L’effet de proximité introduite par le Fe conduit à une modification de la bande de valence au point Γ pour 3 MCs, alors que celle-ci est négligeable pour 7 MCs. Afin d’obtenir un photodétecteur sensible à la polarisation, on s’intéresse à des cristaux ayant une structure anisotrope. La nature anisotrope intra-planaire du cristal IV-V de GeAs est investiguée par spectrométrie d’absorption résolue en polarisation entre 400 et 2000 nm. Les échantillons nanométriques bidimensionnels obtenus de GeAs démontrent bien un dichroïsme linéaire et une photo-détection sensible à la polarisation. Les ratios dichroïques obtenus par des mesures de photocourant atteignent des valeurs élevées de Ipmax/Ipmin ~ 1.49 à 520 nm et de Ipmax/Ipmin ~ 4.4 à 830 nm. Les cartographies de photo-courant suggèrent que la dépendance du courant avec la polarisation trouve son origine majoritairement aux interfaces électrode/GeAs qui présentent un caractère de type Schottky. Des alliages à base d’éléments des groupes IV-VI tels que SnS et ZnSnS ont également été caractérisés. Il est démontré que SnS présente une mobilité des porteurs valant 37,75 cm²•V⁻¹•S⁻¹ et une photo-réponse de 310,5 A/W. En raison de l’absorption optique anisotrope, le photo-courant est dépendant de la direction de polarisation de la lumière incidente, émise à 808 nm. L’absorption optique en bord d’absorption présente une sensibilité à la polarisation avec le plus haut ratio dichroïque atteint valant 3,06 à 862 nm. [...]
Two-dimensional (2D) semiconductor materials exhibit overwhelming electrical, optical, magnetic, thermal and other advantages, which enables their great potential applications in ultra-thin, transparent and highly integrated optoelectronic devices. Searching new two-dimensional materials and exploring their optimal performance, as well as expanding the practical application of two-dimensional materials have been the cores of the researches of two-dimensional materials. This thesis focuses on the vertical magnetic control of the CoFeB film on a large-area single-layer MoS₂ film, which could expand the potential of two-dimensional materials in spin optical detectors, the Polarized Photodetection (anisotropy) based on noval two-dimensional semiconductor GeAs, and the optical characterizations of group IV-VI compounds like SnS and ZnSnS alloys. This paper introduces them in detail through the following three parts: 1. We research the fabrication of the Ta/CoFeB/MgO structures with large perpendicular magnetic anisotropies (PMA) on the full coverage MoS₂ monolayers. By optimizing the thickness of the CoFeB layer and the annealing temperature, a large perpendicular interface anisotropy energy of 0.975 mJ/m² has been obtained at the CoFeB/MgO interface. By analyzing the structural and the chemical properties of the heterostructure, it is found that the insertion of MgO between the ferromagnetic metal (FM) and the 2D material can effectively block the diffusion of the FM atoms into the 2D material, and that the Ta layer plays a critical role to efficiently absorb B atoms from the CoFeB layer to establish the PMA. From the results of ab initio calculations, the MgO thickness can be tuned to modify the MoS₂ band structure, from an indirect bandgap with 7 MLs MgO layers to a direct bandgap with 3 MLs MgO layers. The proximity effect induced by Fe results in a splitting of 10 meV in the valence band at the Γ point of the 3MLs MgO structure while it is negligible for the 7MLs MgO structure. 2. we research the anisotropic optical characterization of a group IV-V compound, Germanium Arsenic (GeAs), with anisotropic monoclinic structure. The in-plane anisotropic optical nature of GeAs crystal is further investigated by the polarization-resolved absorption spectroscopy (400-2000 nm) and the polarization-sensitive photodetectors. In the visible-to-near-infrared range, the 2D GeAs nanoflakes demonstrate the distinct perpendicular optical reversal with an angle of 75~80 degrees on both of the linear dichroism and the polarization-sensitive photodetection. Obvious anisotropic features and the high dichroic ratio of Ipmax/Ipmin ~ 1.49 at 520 nm and Ipmax/Ipmin ~ 4.4 at 830 nm are measured by the polarization-sensitive photodetection. The polarization-dependent photocurrent mapping implied that the polarized photocurrent mainly occurred at the Schottky photodiodes at the electrode/GeAs interface. 3. We research optical characterizations of group-IV-VI compounds like SnS and ZnSnS alloys. SnS nanosheets exhibit carrier mobility of 37.75 cm²·V⁻¹·s⁻¹, photoresponsivity of 310.5 A/W and external quantum efficiency of 8.56×104% at 450 nm. Optical absorption around the absorption edge presents obvious polarization sensitivity with the highest optical absorption dichroic ratio of 3.06 at 862 nm. Due to the anisotropic optical absorption, the polarized photocurrent appears upon the periodic change affected by the polarized direction of the incident light at 808 nm. The ZnSnS alloys combine the advantageous optical parameters of SnS and ZnS₂, which belong to the direct band structure of n-type 2D semiconductors. The carrier mobility of the alloy is 65 cm² V⁻¹ S⁻¹ and the on/off ratio under white-LED illumination is as high as 51

Conventional image sensors achieve color imaging using absorptive organic dye filters. These face considerable challenges however in the trend toward ever higher pixel densities and advanced imaging methods such as multispectral imaging and polarization-resolved imaging. In this dissertation, we investigate the optical properties of vertical silicon nanowires with the goal of image sensor applications. First, we demonstrate a multispectral imaging system that uses a novel filter that consists of vertical silicon nanowires embedded in a transparent medium. Second, we demonstrate pixels consisting of vertical silicon nanowires with integrated photodetectors. We show that their spectral sensitivities are governed by nanowire radius, and perform color imaging. In addition, we demonstrate polarization-resolving photodetectors consisting of silicon nanowires with elliptical cross sections. Finally, we discuss a dual detector device. Each pixel consists of vertical silicon nanowires (incorporating photodetectors) formed above a silicon substrate (that also incorporates a photodetector). Our method is very practical from a manufacturing standpoint because all filter functions are defined at the same time through a single lithography step. In addition, our approach is conceptually different from current filter-based methods, as absorbed light in our device is converted to photocurrent, rather than discarded. This ultimately presents the opportunity for very high photon efficiency.
Engineering and Applied Sciences

The polarization of light is one of the most remarkable phenomena in nature and has led to many discoveries in the optical-telecommunications sphere. The master's thesis describes the basic knowledge about polarized light, which includes the types of light polarization, the issue of Poincaré sphere, polarizing ellipse, etc. Emphasis is also placed on the measurement of optical power, where the analysis of various types of photodetectors and also polarimeters was performed. In the practical part of this work, the design of the workplace itself is described in the diagrams. Also, all devices in the workplace are analyzed and subsequently demonstrated measurement in several scenarios. The final chapter is a discussion with the measured results and graphical dependencies, comparison and analysis of results.

2D Transition-Metal Dichalcogenides (TMDs) have been widely considered as a promising material for future optoelectronics due to the strong light-matter interaction, fantastic electronic properties and environmental stability. However, the relatively large bandgap and low mobility of conventional TMDs (such as MoS2 and WS2) limit their applications in infra optoelectronics and high-speed photodetection. In this chapter, we introduce a new type of group-10 noble TMDs (NTMDs), which exhibit outstanding properties such as unique structural phase, widely tunable energy gap and high mobility. Till now, various NTMDs-based photodetectors have been realized with ultrabroad detection waveband (200 nm to 10.6 μm), fast response time, high responsivity and detectivity, and polarization sensitivity. NTMDs have been excellent potential candidates for next-generation photodetection devices with high-performance, wafer-scalability and flexibility.

Abstract The present chapter develops the theory of interband, intersubband, and excitonic optical processes for semiconductor QWRs, in the same line as in earlier two chapters. The simple rectangular structure and analytical methods are considered first, followed by semi-analytical theories for practical structures. The classification of the one-dimensional nanostructures in terms of growth mechanisms that is, by epitaxial methods and by other chemical methods is next introduced and some examples of top-down and bottom-up methods are given. A few important physical processes and characteristics of nanowires, namely, polarization anisotropy in absorption and emission, and giant birefringence are then discussed. Finally, some of the application areas of nanowires, as light sources, photodetectors, solar cells, and in laser cooling are briefly mentioned.

Infrared optical detection devices such as photodetectors, solar cells, cameras, and microbolometers are becoming smaller in size with a tiny active area in the range of a few micrometers or even nanometers. That comes at the expense of a smaller aperture area of the device, and in turn inefficient collection of infrared energy. Therefore, infrared plasmonic optical antennas are becoming essential to efficiently collect optical energy from free space and concentrate it down to the device’s tiny area. However, it is desirable to develop plasmonic antennas with a broad bandwidth, polarization insensitivity, wide field-of-view, and reasonable plasmonic losses. That ensures collection of most incident infrared radiation and enhancement of power absorption efficiency. In this chapter, some types of plasmonic antennas are explored with an emphasis on innovative type of optical antenna called Bundt Optenna. We investigate Bundt Optenna design and optimization. This antenna has a novel shape that looks like a Bundt baking pan and it is made of gold. Several Bundt unit cells can be arranged in a periodic array that is placed on top of a thin-film infrared absorbing layer. The Bundt Optenna utilizes surface plasmons to squeeze both electric and magnetic fields of infrared radiation down to a 50 nm wide area, thus enhancing absorption efficiency within an underneath thin-film layer. The Optenna demonstrates polarization insensitivity and ultra-broad bandwidth with a large fractional bandwidth within the near, short-wave, and mid-wave infrared bands. It also shows a remarkable enhanced power absorption efficiency and a wide field-of-view.

Abstract In a heterodyne detection system (Martin and Wickramasinghe 1987), shown schematically in Fig. 7.1, the first beam splitter divides into two components. One passes through an acousto-optic modulator that shifts the beam frequency by Om , and the other is reflected onto a mirror as a reference beam. The beam with the shifted frequency, serving as the signal beam, passes through a polarizing beam splitter, a quarter-wave plate, and finally, a microscope objective that focuses it onto the lever supporting the force-sensing tip. The lever reflects the beam back through the microscope objective and quarter-wave plate, which rotates the polarization on the two passes by 90°. The polarizing beam splitter then deflects the beam through an analyzer that adjusts the relative power of the beam incident on the photodetector. The reference beam is deflected by a second mirror, passes through the polarizing beam splitter and analyzer, and is incident on the same photodetector. The reference and signal beams interfere on the photodetector, which generates a current consisting of a spectrum of frequencies. The photocurrent is fed into a single side-band receiver driving a phase-sensitive detector that provides the signal used to display the force acting on the tip.

A dual-polarization (DP) coherent receiver which is insensitive to local oscillator (LO) polarization is proposed and experimentally demonstrated using a single metasurface and five photodetectors. Self-coherent 50-GBd DP-QPSK transmission is accomplished with arbitrary LO polarizations.

A dual-photodetector PIC with an integrated inverse-designed polarization rotator-splitter for polarization demultiplexing is presented. The PIC has a responsivity of 0.15 A/W at 1550 nm and a polarization extinction ratio better than 13 dB for both paths.

Information stored on magneto-optic disks is typically read using a linearly polarized laser beam whose state of polarization is altered by the Faraday and/or polar Kerr effects upon reflection from the recording medium. Polarization sensitive optics are used to convert these media induced polarization changes into irradiance variations at photodetectors. Because the magneto-optic polarization effects are small (typically less than one degree of polarization rotation in the reflected beam) it is essential that the optical system introduce little additional polarization change if the recorded signal is to be recovered faithfully. This paper describes a polarization model that is used to predict the effects that real optical elements will have on the readout signals, noise, and ultimately, the signal to noise ratio of a magneto-optic recording system.