Journal articles: 'Pulsed laser excitation'

1

Chen, Defu, Ying Wang, Buhong Li, Huiyun Lin, Xuechun Lin, and Ying Gu. "Effects of pulse width and repetition rate of pulsed laser on kinetics and production of singlet oxygen luminescence." Journal of Innovative Optical Health Sciences 09, no. 06 (August 2016): 1650019. http://dx.doi.org/10.1142/s179354581650019x.

Full text

Abstract:

Pulsed and continuous-wave (CW) lasers have been widely used as the light sources for photodynamic therapy (PDT) treatment. Singlet oxygen (1O2) is known to be a major cytotoxic agent in type-II PDT and can be directly detected by its near-infrared luminescence at 1270[Formula: see text]nm. As compared to CW laser excitation, the effects of pulse width and repetition rate of pulsed laser on the kinetics and production of 1O2 luminescence were quantitatively studied during photosensitization of Rose Bengal. Significant difference in kinetics of 1O2 luminescence was found under the excitation with various pulse widths of nanosecond, microsecond and CW irradiation with power of 20[Formula: see text]mW. The peak intensity and duration of 1O2 production varied with the pulse widths for pulsed laser excitation, while the 1O2 was generated continuously and its production reached a steady state with CW excitation. However, no significant difference ([Formula: see text]) in integral 1O2 production was observed. The results suggest that the PDT efficacy using pulsed laser may be identical to the CW laser with the same wavelength and the same average fluence rate below a threshold in solution.

APA, Harvard, Vancouver, ISO, and other styles

2

Fisher, Wait G., and Eric A. Wachter. "Improved Signal Processing in Multi-Photon Imaging." Microscopy and Microanalysis 6, S2 (August 2000): 800–801. http://dx.doi.org/10.1017/s1431927600036497.

Full text

Abstract:

Multi-photon excitation has been used in microscopy for nearly a decade, providing a number of demonstrated advantages over other methods for fluorescence imaging. Because excitation is achieved using longer, less energetic light, photodamage and photobleaching of the sample are reduced. Furthermore, since excitation occurs only at the focal point, this approach allows the practical collection of three-dimensionally resolved fluorescence images of live cells. However, due to the small two-photon cross-section of most fluorophores, pulsed lasers are required to generate detectable signal levels. This is due to the quadratic dependence of twophoton absorption on the instantaneous power of the laser. Typically, these lasers are pulsed at very high repetition frequencies, on the order of 106 pulses per second with pulse durations of a few hundreds of femtoseconds. For example, a titanium:sapphire (Ti:S) laser mode-locked at 76 Mhz can provide up to 100,000 watts of instantaneous power and is ideal for exciting two-photon events.

APA, Harvard, Vancouver, ISO, and other styles

3

Razhev, Aleksandr, Dmitriy Churkin, and Alexey Zavyalov. "Pulsed Inductive Molecular Hydrogen Laser." Siberian Journal of Physics 4, no. 3 (October 1, 2009): 12–19. http://dx.doi.org/10.54362/1818-7919-2009-4-3-12-19.

Full text

Abstract:

A pulsed inductive discharge molecular H2 laser has been created for the first time. The excitation system of a toroidal pulsed inductive discharge for molecular hydrogen electron levels excitation was developed. Generation at two wavelengths of 0,89 and 1,12 m was obtained. The spectral, temporal and energy parameters of laser emission under various pressures and pumping conditions were investigated. The maximum pulse power of 6,7 kW was achieved. The measured pulse duration was 18 ± 1 ns. In the cross-section, the laser radiation had the ring shape with an external diameter of 33 mm and thickness of 4 mm.

APA, Harvard, Vancouver, ISO, and other styles

4

Georges, Joseph. "Continuous-Wave-Laser versus Pulsed-Laser Excitation for Crossed-Beam Photothermal Detection in Small Volume Applications: Comparative Features." Applied Spectroscopy 59, no. 9 (September 2005): 1103–8. http://dx.doi.org/10.1366/0003702055012645.

Full text

Abstract:

Crossed-beam thermal lens spectrometry can be implemented using continuous-wave- (cw) laser or pulsed-laser excitation. In both cases, the signal depends on the position of the sample with respect to the probe beam waist, the size of the excitation beam, the beam-size ratio into the sample, and the power or energy of the excitation beam. However, due to differences in the rate of formation and relaxation of the thermal lens, both methods exhibit distinct key features. Optimization of the experimental setup and understanding the thermal lens signal are more complicated under cw-laser excitation than with pulsed-laser excitation. Unlike that observed under pulsed excitation, the effect of the excitation beam waist, of the sample size, and of the flow rate are closely related to the effective size of the thermal element and depend on the chopping frequency. Although the intrinsic sensitivities are almost the same, the performance can significantly differ depending on the chopping frequency or pulse repetition rate, which should be high enough to allow fast data collection and efficient signal averaging.

APA, Harvard, Vancouver, ISO, and other styles

5

Fotiou, Fotios K., and Michael D. Morris. "Photothermal Deflection Densitometer with Pulsed-UV Laser Excitation." Applied Spectroscopy 40, no. 5 (July 1986): 700–704. http://dx.doi.org/10.1366/0003702864508610.

Full text

Abstract:

First application of pulsed photothermal deflection spectroscopy to solid samples is demonstrated. A new densitometer for thin layer chromatography based on this method is described. The technique is suitable for direct measurements in the ultraviolet region. A pulsed excimer laser is used to produce a transient thermal refractive index gradient. The laser delivers pulses of 1–2 mJ at 10–22 pulses/s, at 351 nm. With this system the detection limit for 2,4-dinitroaniline is 750 pg. The signal is linear with amount of analyte for about three orders of magnitude.

APA, Harvard, Vancouver, ISO, and other styles

6

Kozlovsky, Vladimir, Marat Butaev, Yury Korostelin, Stanislav Leonov, Yan Skasyrsky, and Mikhail Frolov. "Study of Fe:ZnSe Laser Exited by Diode Side-Pumped Er:YAG Laser." Photonics 10, no. 8 (July 26, 2023): 869. http://dx.doi.org/10.3390/photonics10080869.

Full text

Abstract:

The performance of a Fe:ZnSe laser was investigated in different schemes of excitation by a pulsed diode side-pumped Er:YAG laser. At the temperature of liquid nitrogen, the Fe:ZnSe laser, pumped by a free running 360-μs Er:YAG laser and demonstrated a pulse energy of 53 mJ with a slope efficiency of 42% relative to absorbed pump energy. When operating at room temperature, two optical schemes were considered. In the first one, the Fe:ZnSe laser crystal was pumped by a Q-switched Er:YAG laser with a passive shutter based on an additional Fe:ZnSe crystalline plate, and the cavities of both lasers were independent. In the second scheme, the cavities of the Fe:ZnSe and Er:YAG lasers were coupled, and the Fe:ZnSe crystal simultaneously served as an active element of the Fe:ZnSe laser and a passive shutter of the Er:YAG laser. Pulses with a duration of less than 200 ns and an energy of ~1 mJ were obtained from the Fe:ZnSe laser with a repetition rate of up to 50 kHz. The experimental waveforms of the laser pulses were approximated by rate equations.

APA, Harvard, Vancouver, ISO, and other styles

7

WANG, Z. P., C. M. GU, and W. Z. SHEN. "PHOTOINDUCED LASER EFFECTS IN INDIUM NITRIDE FILM." Modern Physics Letters B 25, no. 03 (January 30, 2011): 185–92. http://dx.doi.org/10.1142/s021798491102550x.

Full text

Abstract:

The optical nonlinear absorption properties in sputtering Indium nitride ( InN ) film were investigated under the excitations of nanosecond, picosecond and femtosecond pulsed lasers by open-aperture transmission Z-scan technique (TZ-scan). Under the condition of hν > Eg, the saturable absorption (SA) phenomena induced by one-photon transition were observed in both nanosecond and picosencond pulsed TZ-scan measurements. When 2hν > Eg > hν, the film presented SA due to the two-photon transition under the excitation of picosecond laser. However, at femtosecond 800 nm, the film showed the two-photon absorption (TPA) instead of SA, and the TPA coefficient tended to a saturable value as the excitation intensity increased. The results indicate that the InN film is a kind of good saturable absorber.

APA, Harvard, Vancouver, ISO, and other styles

8

Sakamoto, Akira, Yukio Furukawa, Mitsuo Tasumi, and Koji Masutani. "Asynchronous Pulsed-Laser-Excited Fourier Transform Raman Spectroscopy and its Applications." Applied Spectroscopy 47, no. 9 (September 1993): 1457–61. http://dx.doi.org/10.1366/0003702934067504.

Full text

Abstract:

An asynchronous pulsed-laser-excited Fourier transform Raman spectrophotometer based on a conventional continuous-scan interferometer has been developed. The additional assembly required for pulsed-laser-excited measurements, which consists of a pulsed Nd:YAG laser, a gate circuit, and a low-pass filter, can be attached to any conventional FT-Raman spectrophotometer. The principle of the signal-processing of this method is almost the same as that of the asynchronous time-resolved Fourier transform infrared spectroscopy reported previously. This method does not require the synchronization between the Raman excitation and the sampling of the A/D converter. As an application of this method, it is demonstrated that the use of a pulsed laser and a gate circuit can give a significant increase in signal-to-noise ratios over continuous-wave measurements with the same average laser power. It is also shown that when a constant background (for example, thermal radiation from samples at high temperatures) or a long-lived background is present, the use of pulsed excitation and a gate circuit can effectively reduce the background. Moreover, pulsed excitation can be used for recording time-resolved Raman spectra by using an FT-Raman spectrophotometer. The time resolution is governed only by the width of the probe laser pulse. The potentiality of this method is demonstrated.

APA, Harvard, Vancouver, ISO, and other styles

9

Kaselouris, E., I. K. Nikolos, Y. Orphanos, E. Bakarezos, N. A. Papadogiannis, M. Tatarakis, and V. Dimitriou. "A Review of Simulation Methods of Laser Matter Interactions Focused on Nanosecond Laser Pulsed Systems." Journal of Multiscale Modelling 05, no. 04 (December 2013): 1330001. http://dx.doi.org/10.1142/s1756973713300013.

Full text

Abstract:

A review study of the developments in the field of pulsed laser-solid interaction simulation methods, for moderate laser energies, is presented. The paper is focused on the methods that numerically simulate the interactions of pulsed ns-laser with solid metal targets. Three main regimes for pulsed laser excitation, are well established, namely, the thermoelastic, melting and plasma regimes. The modelling and simulation techniques that may numerically describe these three regimes and the occurring dynamic matter responses are reviewed. Modelling efforts concerning various fields of applications of lasers are briefly discussed.

APA, Harvard, Vancouver, ISO, and other styles

10

Tereszchuk, K. A., J. M. Vadillo, and J. J. Laserna. "Glow-Discharge-Assisted Laser-Induced Breakdown Spectroscopy: Increased Sensitivity in Solid Analysis." Applied Spectroscopy 62, no. 11 (November 2008): 1262–67. http://dx.doi.org/10.1366/000370208786401491.

Full text

Abstract:

A glow discharge operating in steady-state and pulsed temporal conditions is used to excite the material previously excited by a pulsed laser ablation system. The system provides a simple means by which to potentially excite the material ablated by the incident laser pulse by taking advantage of enhanced collisional excitation. In this way, one can effectively reduce laser pulse energies below the excitation and ionization thresholds to potentially those required solely for laser ablation of the material, reducing sample damage and improving the lateral resolution. Several critical parameters such as the gas pressure, gas type, and discharge voltage were evaluated, demonstrating the potential of the technique for spatially resolved analysis. The new dual glow-discharge laser-induced breakdown spectroscopy (GD-LIBS) synchronous scheme provides significant signal enhancements when compared to LIBS or GD under identical conditions.

APA, Harvard, Vancouver, ISO, and other styles

11

Buffa, Roberto, and Stefano Cavalieri. "Laser-induced autoionization with pulsed excitation." Physical Review A 42, no. 9 (November 1, 1990): 5481–85. http://dx.doi.org/10.1103/physreva.42.5481.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Pashina, Olesia, Daniil Ryabov, George Zograf, Sergey Makarov, and Mihail Petrov. "Ultrafast laser heating of non-plasmonic nanocylinders." Journal of Physics: Conference Series 2015, no. 1 (November 1, 2021): 012104. http://dx.doi.org/10.1088/1742-6596/2015/1/012104.

Full text

Abstract:

Abstract We develop a model describing non-equilibrium processes under the excitation of resonant semiconductor nanostructures with ultrashort laser pulses with a duration of about 100 fs. We focus on the heating effects related to pulsed excitation with account on free carriers generation, thermalization, and relaxation. The heat exchange between the electron and phonon system is treated within the two-temperature model. We applied the developed model to describing pulsed heating of silicon nanocylinder on top of a dielectric substrate. We come up with estimations of the thermal damage threshold of the considered structures which provides the limits for the experimental conditions and ensures thermal stability of the samples.

APA, Harvard, Vancouver, ISO, and other styles

13

Li, Hang, Xinhui Zhang, Xinyu Liu, Margaret Dobrowolska, and Jacek Furdyna. "Ultrafast Modulation of Magnetization Dynamics in Ferromagnetic (Ga, Mn)As Thin Films." Applied Sciences 8, no. 10 (October 11, 2018): 1880. http://dx.doi.org/10.3390/app8101880.

Full text

Abstract:

Magnetization precession induced by linearly polarized optical excitation in ferromagnetic (Ga,Mn)As was studied by time-resolved magneto-optical Kerr effect measurements. The superposition of thermal and non-thermal effects arising from the laser pulses complicates the analysis of magnetization precession in terms of magnetic anisotropy fields. To obtain insight into these processes, we investigated compressively-strained thin (Ga,Mn)As films using ultrafast optical excitation above the band gap as a function of pulse intensity. Data analyses with the gyromagnetic calculation based on Landau-Lifshitz-Gilbert equation combined with two different magneto-optical effects shows the non-equivalent effects of in-plane and out-of-plane magnetic anisotropy fields on both the amplitude and the frequency of magnetization precession, thus providing a handle for separating the effects of non-thermal and thermal processes in this context. Our results show that the effect of photo-generated carriers on magnetic anisotropy constitutes a particularly effective mechanism for controlling both the frequency and amplitude of magnetization precession, thus suggesting the possibility of non-thermal manipulation of spin dynamics through pulsed laser excitations.

APA, Harvard, Vancouver, ISO, and other styles

14

Sakamoto, Akira, Hiromi Okamoto, and Mitsuo Tasumi. "Observation of Picosecond Transient Raman Spectra by Asynchronous Fourier Transform Raman Spectroscopy." Applied Spectroscopy 52, no. 1 (January 1998): 76–81. http://dx.doi.org/10.1366/0003702981942357.

Full text

Abstract:

Asynchronous Fourier transform (FT) Raman spectroscopy with 100 picosecond time resolution has been developed. A signal-processing assembly required for time-resolved and transient Raman measurements consists of a picosecond Nd:YLF laser system, a gate circuit, and a low-pass filter, and it can be attached to any conventional continuous-scan FT-Raman spectrophotometer. The principle of signal processing employed in this method is almost the same as that of asynchronous pulsed-laser-excited FT-Raman spectroscopy. This method does not require synchronization between Raman excitation by probe laser pulses and sampling by the analog-to-digital converter. Transient Raman spectra have been obtained from the first excited singlet state of three anthracene derivatives in cyclohexane solutions and photoexcited poly( p-phenylenevinylene) [(C6H4CH=CH) n] by using 351 nm light (pulse width ã 70 ps) for photoexcitation and 1053 nm light (pulse width ã 100 ps) for Raman excitation.

APA, Harvard, Vancouver, ISO, and other styles

15

Hu, Gangbo, Xue Yang, Xiangyu Wang, Wei Fang, and Ning Tao. "Study of multi-long-pulse thermography using high-power fiber lasers." AIP Advances 13, no. 2 (February 1, 2023): 025029. http://dx.doi.org/10.1063/5.0131518.

Full text

Abstract:

Active infrared thermography tests are performed using a high-power continuous fiber laser as the excitation source. Multi-long-pulses (MLPs) are used to detect deep defects in samples with reduced heating. Simulation results are compared to theoretical predictions based on 1D heat conduction equations. Different excitation modes are compared. Thermal images are processed using pulsed phase thermography and principal component thermography (PCT), showing that the combination of MLP thermal excitation and PCT data analysis provides better defect detection capability and reduces the specimen’s surface temperature in comparison to conventional pulsed thermography.

APA, Harvard, Vancouver, ISO, and other styles

16

Razhev, A. M., E. S. Kargapol `tsev, D. S. Churkin, and I. A. Trunov. "Pulsed inductive CO₂ laser with radio-frequency excitation and influence of the H₂ content on the efficiency and lasing temporal characteristics." Laser Physics 33, no. 1 (December 2, 2022): 015002. http://dx.doi.org/10.1088/1555-6611/aca291.

Full text

Abstract:

Abstract In 2021, data on the effective pulsed gas discharge inductive CO2 laser with radio-frequency (RF) excitation were published with a pulse output energy of E∼ 1 J (the efficiency η∼ 14.5%) on the gas mixture He:N2:CO2 = 8:2:1. The efficiency of the developed CO2 laser had exceeded the value η∼ 21% at E∼ 350 mJ. At the beginning of 2022, it was shown that xenon addition (Xe = 4%) to the gas mixture made it possible to achieve an efficiency of η∼ 27% at an output energy of E∼ 600 mJ. For the first time, the effect of hydrogen additives in the active medium (He:N2:CO2:H2 and N2:CO2:H2 gas mixtures) was investigated for a pulsed inductive CO2 laser with RF excitation depending on the RF-pumping pulse duration value (τ), which allows the energy and temporal radiation characteristics of the laser to be controlled over a wider range. In addition to those already published, new experimental data have been obtained, namely the output beam profile of the inductive CO2 laser based on He:N2:CO2 = 8:2:1 gas mixture depending on the τ value. The new data will improve our understanding of inductive CO2 laser physics and of the plasma–chemical processes occurring in its active medium. RF current pulses propagated along inductor wires and, thus, an inductive discharge was formed to create a population inversion by IR transitions of CO2 * molecules.

APA, Harvard, Vancouver, ISO, and other styles

17

HAZAMA, HISANAO, KATSUNORI ISHII, and KUNIO AWAZU. "LESS-INVASIVE LASER THERAPY AND DIAGNOSIS USING A TABLETOP MID-INFRARED TUNABLE LASER." Journal of Innovative Optical Health Sciences 03, no. 04 (October 2010): 285–92. http://dx.doi.org/10.1142/s179354581000109x.

Full text

Abstract:

Since numerous characteristic absorption lines caused by molecular vibration exist in the mid-infrared (MIR) wavelength region, selective excitation or selective dissociation of molecules is possible by tuning the laser wavelength to the characteristic absorption lines of target molecules. By applying this feature to the medical fields, less-invasive treatment and non-destructive diagnosis with absorption spectroscopy are possible using tunable MIR lasers. A high-energy nanosecond pulsed MIR tunable laser was obtained with difference-frequency generation (DFG) between a Nd:YAG and a tunable Cr:forsterite lasers. The MIR-DFG laser was tunable in a wavelength range of 5.5–10 μm and generated laser pulses with energy of up to 1.4 mJ, a pulse width of 5 ns, and a pulse repetition rate of 10 Hz. Selective removal of atherosclerotic lesion was successfully demonstrated with the MIR-DFG laser tuned at a wavelength of 5.75 μm, which corresponds to the characteristic absorption of the ester bond in cholesterol esters in the atherosclerotic lesions. We have developed a non-destructive diagnostic probe with an attenuated total reflection (ATR) prism and two hollow optical fibers. An absorption spectrum of cholesterol was measured with the ATR probe by scanning the wavelength of the MIR-DFG laser, and the spectrum was in good agreement with that measured with a commercial Fourier transform infrared spectrometer.

APA, Harvard, Vancouver, ISO, and other styles

18

Alnayli, Raad Sh, and Hanan Alkazaali. "Properties Studies of Silver Nanoparticles Colloids in Ethanol Prepared by Means Pulses Laser." Journal of Nano Research 60 (November 2019): 154–61. http://dx.doi.org/10.4028/www.scientific.net/jnanor.60.154.

Full text

Abstract:

In this work we study the influence of the laser pulses silver nanoparticles productivity during laser ablation of silver immersed in liquid. Ag nanoparticles were synthesized by pulsed laser ablation of Ag targets in ethanol using the (1064 nm, Q-switched, Nd:YAG) laser with energy of 140 mJ per pulse. UV-Visible absorption spectra were used for the characterization and comparison of products. The non-linear refractive index and absorption coefficient of silver nanoparticles were investigated using a single beam z-scan technique; the excitation source was a continuous wave (CW) of 650 nm diode laser with a beam power of 50 mW. All investigated samples showed negative-induced non-linear refractive indices.

APA, Harvard, Vancouver, ISO, and other styles

19

Kuritsyn, Yu A., G. N. Makarov, I. Pak, M. V. Sotnikov, I. I. Zasavitsky, and A. P. Shotov. "Diode Laser Spectroscopy of the Dynamics of Multiphoton Excitation of SF6 Molecules by CO2 Laser Pulses." Laser Chemistry 8, no. 2-4 (January 1, 1988): 151–68. http://dx.doi.org/10.1155/lc.8.151.

Full text

Abstract:

The dynamics of excitation by CO2 laser pulses of SF6 molecules from individual rotational sublevels J″ of the ground vibrational state have been investigated in a pulsed molecular jet under essentially collisionless conditions. At different energy fluences of exciting laser pulse Φ = 10−5 + 10−1 J/cm2, the dependences of the fraction fJ of excited molecules on the rotational quantum number J″ have been obtained, when SF6 molecules were excited on the 10P(16) CO2 laser line, as well as on the 10P(18) and 10P(14) lines at Φ = 0.1 J/cm2. Comparison of experimental results with theoretical predictions18–20 shows rather strong disagreement between theory and experiments both in the population of the υ3 = 1 state and in the role of multiphoton transitions. It is shown that the narrowing of the exciting laser pulse spectrum (the 10P(16) line, Φ ≲ 10−2 J/cm2) results in drastic decrease of the fraction of excited molecules from the (υ3 = 0, J″ = 4) state which is most resonant with laser radiation.

APA, Harvard, Vancouver, ISO, and other styles

20

Tabara, Tomohiro, Naoki Wakiya, Takanori Kiguchi, M. Tanaka, and Kazuo Shinozaki. "Fabrication of HfO₂ Thin Film on Si Substrate by Double-Pulse Excitation PLD." Key Engineering Materials 350 (October 2007): 129–32. http://dx.doi.org/10.4028/www.scientific.net/kem.350.129.

Full text

Abstract:

Thin films of HfO2 were fabricated on a p-Si(001) substrate using double pulse excitation (DPE) pulsed laser deposition (PLD) with KrF excimer and Nd:YAG lasers, and using conventional Nd:YAG laser PLD under two typical oxygen pressures (7.3 × 10-2 and 7.3 × 10-1 Pa). At 400°C or higher temperatures, the films are crystalline; at less than 400°C, they are amorphous. At higher oxygen pressures, DPE-PLD was effective against droplets. Then the surface morphology and electrical insulation properties of thin films were improved. At lower pressure, DPE-PLD was ineffective.

APA, Harvard, Vancouver, ISO, and other styles

21

Кюрегян, А. С. "Возбуждение лазеров на парах меди прямым разрядом накопительного конденсатора через быстродействующие фототиристоры." Журнал технической физики 126, no. 4 (2019): 471. http://dx.doi.org/10.21883/os.2019.04.47518.258-18.

Full text

Abstract:

AbstractThe possibility of using a “pulsed fiber laser–photothyristor” optocoupler as a switch in the excitation schemes of copper vapor lasers (CVLs) has been investigated. It has been shown that such a switch has a nanosecond performance and is able to form monopolar and alternating current pulses through CVLs with a power of up to 10 MW and a repetition rate of tens of kilohertz when an electrical efficiency of the excitation circuit is more than 95%. A simple but very accurate model of a photothyristor is proposed, which can be used in full-scale CVL modeling programs.

APA, Harvard, Vancouver, ISO, and other styles

22

Bai, Xueshi, and Vincent Detalle. "Time-Gated Pulsed Raman Spectroscopy with NS Laser for Cultural Heritage." Heritage 6, no. 2 (February 1, 2023): 1531–40. http://dx.doi.org/10.3390/heritage6020082.

Full text

Abstract:

Raman spectroscopy, a non-destructive reference technique, is used in heritage science to directly identify materials like pigments, minerals, or binding media. However, depending on the material, the laser source can induce a strong fluorescence signal that may mask the Raman signal during spectral detection. This photo-induced effect can prevent the detection of a Raman peak. A pulsed Raman spectroscopy, using a time-gated detection and pulsed laser, is proven capable of rejecting the fluorescence background and working with the environmental light, which makes Raman spectroscopy more adapted for in situ applications. In this paper, we investigated how an ns pulsed laser can be an excitation source of Raman spectroscopy by focusing on different parameters of laser excitation and collection. With proper implementation, this pulsed Raman technique can be used for cultural heritage with an ns pulsed laser for the first time.

APA, Harvard, Vancouver, ISO, and other styles

23

Razhev A M, Kargapol`tsev E. S., and Trunov I. A. "Pulsed RF excitation inductive discharge CO-=SUB=-2-=/SUB=- laser with the radiation energy of 1 J and high efficiency." Optics and Spectroscopy 132, no. 3 (2022): 368. http://dx.doi.org/10.21883/eos.2022.03.53559.2836-21.

Full text

Abstract:

An efficient pulsed gas-discharge inductive CO2-laser with a radiation energy of 1.05 J has been developed for the first time. In this case, the pulse duration of the laser radiation was about 10 msec. The maximum efficiency of 21.1% was obtained at a radiation energy of 340 mJ. RF current pulses propagated along the inductor conductor and, thus, an inductive discharge was formed to create an inverse population at the infrared (IR) transitions of CO2* molecules. The temporal and energy characteristics of the radiation of the inductive CO2-laser depending on the duration of the pump pulse are investigated. The spatial characteristics and spectrum of the radiation of the developed laser are estimated. The divergence of the laser radiation was 0.52 mrad. The cross-sectional dimension of the laser output beam was about 35 mm in diameter. Keywords: inductive discharge in a mixture of gases, high-frequency modulation of the pump voltage, population inversion, output characteristics of laser radiation.

APA, Harvard, Vancouver, ISO, and other styles

24

Fan, G. Y., H. Fujisaki, R. K. Tsay, R. Y. Tsien, and Mark H. Ellisman. "Video-Rate Scanning Two-Photon Excitation Fluorescence Microscopy." Microscopy and Microanalysis 4, S2 (July 1998): 424–25. http://dx.doi.org/10.1017/s1431927600022248.

Full text

Abstract:

A video-rate scanning two-photon excitation microscope (TPEM) has been successfully constructed and tested. The TPEM, based on a Nikon RCM-8000, incorporates a femtosecond pulsed laser, a pre-chirper, and a non-confocal detection box for ratio imaging. Fig. 1 shows the schematic layout of the main components of the instrument, each of which is briefly discussed below.Laser System: A Tsunami Ti: Sapphire laser (from Spectra-Physics) is optically pumped by a 5 W green laser (Millennia from Spectra-Physics) and is capable of generating 100 fs pulses at a repetition rate of 82 MHz and an average power of 0.8 W. The output wavelength is tunable from 690 to 1050 nm with three optical sets, each covering part of the spectrum with some overlapping.Pre-chirper: After leaving the Tsunami, the laser beam enters an optic unit known as a pre-chirper which pre-chirps laser pulses to compensate for the group velocity dispersion which will result when the laser beam goes through the microscope optics.

APA, Harvard, Vancouver, ISO, and other styles

25

Minamikawa, Takeo, Yoshinori Murakami, Naokazu Matsumura, Hirohiko Niioka, Shuichiro Fukushima, Tsutomu Araki, and Mamoru Hashimoto. "Photo-Induced Cell Damage Analysis for Single- and Multifocus Coherent Anti-Stokes Raman Scattering Microscopy." Journal of Spectroscopy 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/5725340.

Full text

Abstract:

In this study, we investigated photo-induced damage to living cells during single- and multifocus excitations for coherent anti-Stokes Raman scattering (CARS) imaging. A near-infrared pulsed laser (709 nm) was used to induce cell damage. We compared the photo-induced cell damage in the single- and the multifocus excitation schemes with the condition to obtain the same CARS signal in the same frame rate. For the evaluation of cell viability, we employed 4′,6-diamidino-2-phenylindole (DAPI) fluorophores that predominantly stained the damaged cells. One- and two-photon fluorescence of DAPI fluorophores were, respectively, excited by an ultraviolet light source and the same near-infrared light source and were monitored to evaluate the cell viability during near-infrared pulsed laser irradiation. We found lower uptake of DAPI fluorophores into HeLa cells during the multifocus excitation compared with the single-focus excitation scheme in both the one- and the two-photon fluorescence examinations. This indicates a reduction of photo-induced cell damage in the multifocus excitation. Our findings suggested that the multifocus excitation scheme is expected to be suitable for CARS microscopy in terms of minimal invasiveness.

APA, Harvard, Vancouver, ISO, and other styles

26

Garming, Mathijs W. H., Pieter Kruit, and Jacob P. Hoogenboom. "Imaging resonant micro-cantilever movement with ultrafast scanning electron microscopy." Review of Scientific Instruments 93, no. 9 (September 1, 2022): 093702. http://dx.doi.org/10.1063/5.0089086.

Full text

Abstract:

Here, we demonstrate ultrafast scanning electron microscopy (SEM) for making ultrafast movies of mechanical oscillators at resonance with nanoscale spatiotemporal resolution. Locking the laser excitation pulse sequence to the electron probe pulses allows for video framerates over 50 MHz, well above the detector bandwidth, while maintaining the electron beam resolution and depth of focus. The pulsed laser excitation is tuned to the oscillator resonance with a pulse frequency modulation scheme. We use an atomic force microscope cantilever as a model resonator, for which we show ultrafast real-space imaging of the first and even the 2 MHz second harmonic oscillation as well as verification of power and frequency response via the ultrafast movies series. We detect oscillation amplitudes as small as 20 nm and as large as 9 μm. Our implementation of ultrafast SEM for visualizing nanoscale oscillatory dynamics adds temporal resolution to the domain of SEM, providing new avenues for the characterization and development of devices based on micro- and nanoscale resonant motion.

APA, Harvard, Vancouver, ISO, and other styles

27

Sonnenschein, Volker, and Hideki Tomita. "A Hybrid Self-Seeded Ti:sapphire Laser with a Pumping Scheme Based on Spectral Beam Combination of Continuous Wave Diode and Pulsed DPSS Lasers." Applied Sciences 12, no. 9 (May 7, 2022): 4727. http://dx.doi.org/10.3390/app12094727.

Full text

Abstract:

A wide variety of applications require high peak laser intensity in conjunction with a narrow spectral linewidth. Typically, injection-locked amplifiers have been employed for this purpose, where a continuous wave oscillator is amplified in a secondary external resonant amplifier cavity using a pulsed pump laser. In contrast, here we demonstrate a setup that combines a CW Ti:sapphire oscillator and pulsed amplifier in a single optical cavity, resulting in a compact system. Dichroic beam combination of blue wavelength semiconductor diodes and the green wavelength of a Nd:YAG laser allowed the simultaneous excitation of the Ti:sapphire crystal by both continuous wave and pulsed pump sources. A linewidth of <2 MHz is achieved in continuous wave operation, while the linewidth increases to about 10 MHz in the combined CW+pulsed mode with a pulse duration of 73 ns. A peak pulse intensity of 0.2 kW is achieved, which should enable efficient single-pass second harmonic generation in a nonlinear crystal.

APA, Harvard, Vancouver, ISO, and other styles

28

Li, J., X. Liao, Z. Meng, and Y. Jiang. "Method for efficient excitation of selective vibration modes in pulsed laser photothermal actuation." Journal of Applied Physics 133, no. 11 (March 21, 2023): 114501. http://dx.doi.org/10.1063/5.0140358.

Full text

Abstract:

Photothermal excitation based on thermoelastic mechanisms is widely used in non-destructive testing, precision operations, and driving micro-resonators. The narrow drive bandwidth of the high vibration mode in photothermal excitation limits its application to multi-mode drives. Controlling the laser’s irradiation position is an effective solution. In this study, we build a theoretical model to achieve selective and efficient excitation of different flexural vibration modes of beams with different supports. The model can be extended to other thermal and physical boundaries, which is validated by numerical simulations and experimental results. The results show that higher modes with complex periodic shapes can be efficiently excited by focusing the laser at the peak of the absolute value of the second derivative of the flexural mode while focusing the laser at the inflection point of the mode shape will result in extremely small amplitudes. Our study indicates that the thermal gradient plays a vital role in the oscillation of the beam. The conventional view assumes that the resonance of the photo-thermal excitation beam is caused by the local expansion and contraction of the material, which cannot completely explain the dependence principle of the photothermal vibration on the laser irradiation position. To investigate the mechanism of beam resonance under laser excitation, three excitation modes, unidirectional excitation, bidirectional in-phase excitation, and bidirectional anti-phase excitation, were established, and the conversion process of optical energy to mechanical energy under laser excitation was analyzed. These results provide new options for optimal excitation and multi-mode energy flow control in photothermal driving.

APA, Harvard, Vancouver, ISO, and other styles

29

Михеев, К. Г., Р. Г. Зонов, Д. Л. Булатов, А. Е. Фатеев, and Г. М. Михеев. "Лазерно-индуцированный графен на полиимидной пленке: наблюдение эффекта увлечения." Письма в журнал технической физики 46, no. 9 (2020): 51. http://dx.doi.org/10.21883/pjtf.2020.09.49375.18152.

Full text

Abstract:

Porous graphene film structures were produced by irradiation of polyimide film with focused continuous wave CO2 laser. Generation of nanosecond pulses of photocurrent was observed in the obtained structures upon excitation by nanosecond laser pulses in a wide range of wavelengths. It is shown that the photocurrent linearly increases with pulsed laser power and its dependence on the angle of light incidence on the film structure is symmetric about the origin. Wavelength dependence of light-to-photocurrent conversion coefficient was measured. The obtained results are explained by photon-drag effect photocurrent generation.

APA, Harvard, Vancouver, ISO, and other styles

30

Jones, Roger W., and John F. McClelland. "Transient infrared emission spectroscopy by pulsed laser excitation." Analytical Chemistry 61, no. 17 (September 1989): 1810–15. http://dx.doi.org/10.1021/ac00192a006.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Baker, C., I. S. Gregory, W. R. Tribe, I. V. Bradley, M. J. Evans, M. Withers, P. F. Taday, et al. "Terahertz pulsed imaging with 1.06 μm laser excitation." Applied Physics Letters 83, no. 20 (November 17, 2003): 4113–15. http://dx.doi.org/10.1063/1.1627485.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Mohanty, Jyotirmayee, Dipak K. Palit, Laxminarayan V. Shastri, and Avinash V. Sapre. "Pulsed laser excitation of phosphate stabilised silver nanoparticles." Journal of Chemical Sciences 112, no. 1 (February 2000): 63–72. http://dx.doi.org/10.1007/bf02704301.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Settersten, Thomas B., and Mark A. Linne. "Modeling pulsed excitation for gas-phase laser diagnostics." Journal of the Optical Society of America B 19, no. 5 (May 1, 2002): 954. http://dx.doi.org/10.1364/josab.19.000954.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Vagizov, F. G., E. K. Sadykov, and O. A. Kocharovskaya. "Modulation of Mössbauer radiation by pulsed laser excitation." JETP Letters 96, no. 12 (February 2013): 812–16. http://dx.doi.org/10.1134/s0021364012240137.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Sreelatha, K., C. Venugopal, S. K. Chaudhary, and N. V. Unnikrishnan. "Nonlinear Luminescence in CdI2 under Pulsed Laser Excitation." Crystal Research and Technology 34, no. 7 (August 1999): 897–900. http://dx.doi.org/10.1002/(sici)1521-4079(199908)34:7<897::aid-crat897>3.0.co;2-x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Cheung, Jeff, and Jim Horwitz. "Pulsed Laser Deposition History and Laser-Target Interactions." MRS Bulletin 17, no. 2 (February 1992): 30–36. http://dx.doi.org/10.1557/s0883769400040598.

Full text

Abstract:

The laser, as a source of “pure” energy in the form of monochromatic and coherent photons, is enjoying ever increasing popularity in diverse and broad applications from drilling micron-sized holes on semiconductor devices to guidance systems used in drilling a mammoth tunnel under the English Channel. In many areas such as metallurgy, medical technology, and the electronics industry, it has become an irreplaceable tool.Like many other discoveries, the various applications of the laser were not initially defined but were consequences of natural evolution led by theoretical studies. Shortly after the demonstration of the first laser, the most intensely studied theoretical topics dealt with laser beam-solid interactions. Experiments were undertaken to verify different theoretical models for this process. Later, these experiments became the pillars of many applications. Figure 1 illustrates the history of laser development from its initial discovery to practical applications. In this tree of evolution, Pulsed Laser Deposition (PLD) is only a small branch. It remained relatively obscure for a long time. Only in the last few years has his branch started to blossom and bear fruits in thin film deposition.Conceptually and experimentally, PLD is extremely simple, probably the simplest among all thin film growth techniques. Figure 2 shows a schematic diagram of this technique. It uses pulsed laser radiation to vaporize materials and to deposit thin films in a vacuum chamber. However, the beam-solid interaction that leads to evaporation/ablation is a very complex physical phenomenon. The theoretical description of the mechanism is multidisciplinary and combines equilibrium and nonequilibrium processes. The impact of a laser beam on the surface of a solid material, electromagnetic energy is converted first into electronic excitation and then into thermal, chemical, and even mechanical energy to cause evaporation, ablation, excitation, and plasma formation.

APA, Harvard, Vancouver, ISO, and other styles

37

Anguiano, S., A. E. Bruchhausen, and A. Fainstein. "OPTOMECHANICAL TRANSDUCTION AND OPTICAL BISTABILITIES IN BRAGG-REFLECTOR-BASED MICRORESONATORS." Anales AFA 33, no. 3 (October 15, 2022): 59–64. http://dx.doi.org/10.31527/analesafa.2022.33.3.59.

Full text

Abstract:

In cavity optomechanics experiments with ultrashort laser pulses, the temporal dynamics of the optical modes of the system play a fundamental role in the generation and detection of coherent phonons. In this work, we analyze the feasibility of using a second continuous emission laser to optimize the detection efficiency, by setting the fundamentalótical mode to a specific spectral position. Under certain conditions, and through this continuum excitation, it is possible to modify the recovery dynamics of the optical modes after an ultrafast pulsed excitation, to the point of stopping it on a quasiequilibrium. This phenomenon is directly related to the optical bistability of the resonator.

APA, Harvard, Vancouver, ISO, and other styles

38

van Wilderen, L. J. G. W., C. Neumann, A. Rodrigues-Correia, D. Kern-Michler, N. Mielke, M. Reinfelds, A. Heckel, and J. Bredenbeck. "Picosecond activation of the DEACM photocage unravelled by VIS-pump-IR-probe spectroscopy." Physical Chemistry Chemical Physics 19, no. 9 (2017): 6487–96. http://dx.doi.org/10.1039/c6cp07022a.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Quintana-Silva, Guillermo, Hugo Sobral, and Jesus Rangel-Cárdenas. "Characterization of CdTe Thin Films Using Orthogonal Double-Pulse Laser-Induced Breakdown Spectroscopy." Chemosensors 11, no. 1 (December 21, 2022): 4. http://dx.doi.org/10.3390/chemosensors11010004.

Full text

Abstract:

Orthogonal reheating double-pulse laser-induced breakdown spectroscopy (LIBS) was applied to the elemental analysis of CdTe thin film samples. Films were grown through nanosecond pulsed laser ablation over silicon and glass substrates. The analysis was performed by applying a 266 nm pulsed laser devised to minimize sample damage. Re-excitation was conducted using a nanosecond laser emitting at 1064 nm that induced air breakdown 1 mm above the target. Emission enhancement was investigated as a function of both time acquisition delay and inter-pulse delay. The plasma temperature and electron density calculations made showed that the double-pulse scheme produced higher temperature values and a longer plasma duration than single-pulse LIBS. The self-absorption coefficient of the lines was determined from the measured ablated matter, plasma volume and collected spectra. The results of the double-pulse LIBS configuration showed a significant increase in emission intensity, reducing the self-absorption effect. In addition, the relative concentration of the thin films was determined for both experimental schemes. The calculated elemental values for the double-pulse configuration coincide with those expected and are more accurate than those obtained using a single laser.

APA, Harvard, Vancouver, ISO, and other styles

40

Klassen, N. V., and P. V. Provotorov. "Spatial and spectral features of the luminescence of liquid nitrogen stimulated by infrared lasers." Journal of Physics: Conference Series 2056, no. 1 (October 1, 2021): 012038. http://dx.doi.org/10.1088/1742-6596/2056/1/012038.

Full text

Abstract:

Abstract Spectral features of cryogenic liquids, especially nitrogen, seem to be clearly investigated due to the wide application in science. On the other hand, material properties can really be different under intensive laser irradiation. During irradiation of liquid nitrogen with pulsed (pulse duration 20 ns) YaG: Nd 1064 nm laser with average power of 0.3 W we have found bright luminescence in the visible region with five narrow spectral lines. This phenomenon can be explained by the multiphoton excitation of nitrogen molecules and ions with infrared photons. Its spatial and spectral characteristics are attributed to Amplified Spontaneous Emission. The main features include super-linear dependence of the emission intensity on the intensity of the excitation radiation, limited amount of narrow spectral bands and conical geometry of the emission with the clear separation of the cones in correspondence with the spectral lines of the emission. This phenomenon manifests liquid nitrogen as the convenient substance of Kerr type for studies of various non-linear optical processes by means of nanosecond lasers instead of femtosecond lasers applied usually for these purposes.

APA, Harvard, Vancouver, ISO, and other styles

41

Bennett, T. D., and M. Farrelly. "Vaporization Kinetics During Pulsed Laser Heating of Liquid Hg." Journal of Heat Transfer 122, no. 2 (October 7, 1999): 345–50. http://dx.doi.org/10.1115/1.521470.

Full text

Abstract:

There is a growing body of experimental evidence showing that the kinetics of nascent vapor produced during pulsed laser heating of metals cannot always be ascribed to the surface thermal conditions. Some investigators have proposed that the discharge of energetic (nonthermal) atoms from metals can involve light coupling to surface plasmons. This requires surface roughness to facilitate wave vector matching of laser light with surface electromagnetic excitation modes. If true, superthermal vaporization kinetics should disappear from time-of-flight measurements when an optically smooth surface is used. Unfortunately, maintaining such an ideal surface is infeasible on a solid target because each laser pulse introduces nanometer sized roughness through the process of melting and resolidification. We have investigated the nature of vaporization from a liquid Hg surface using a nanosecond laser emitting 5 eV photons. Surface tension of the liquid provides an optically smooth surface for this experiment. Nevertheless, we observe superthermal vaporization kinetics from liquid Hg. Yet, the shape of the energy distribution is Boltzmann (the thermal expectation), and the energy distribution does not demonstrate any quanta characteristic of vaporization mediated by an electronic excitation. [S0022-1481(00)01602-9]

APA, Harvard, Vancouver, ISO, and other styles

42

Lewis, Cris, Stephen K. Doorn, David M. Wayne, Fred L. King, and Vahid Majidi. "Characterization of a Pulsed Glow Discharge Laser Ablation System Using Optical Emission." Applied Spectroscopy 54, no. 8 (August 2000): 1236–44. http://dx.doi.org/10.1366/0003702001950823.

Full text

Abstract:

Investigations involving laser-based sampling of copper into an auxiliary pulsed glow discharge for ionization and excitation are presented. The interaction of the ablated copper with the auxiliary glow discharge was studied by monitoring the copper atom emission signal at 368.744 nm. Results demonstrate the ability to time ablation appropriately to access specific temporal regions of the pulsed plasma. More specifically, laser-ablated material was introduced into the glow discharge negative glow during the afterpeak. Ionization and excitation was accomplished by collisions with a metastable argon population produced by the glow discharge (Penning ionization) followed by recombination to yield excited-state Cu atoms. The work presented investigates parameters that affect the atomic emission signal intensity of the ablated material, including cathode-to-target distance, discharge gas pressure, and relative timing of discharge and ablation. Results demonstrate that decreasing the glow discharge working gas pressure increases the transport efficiency of laser-ablated material into the negative glow. These investigations are part of an ongoing series of studies on sample introduction schemes that utilize different ionization and excitation mechanisms found in pulsed glow discharge plasmas.

APA, Harvard, Vancouver, ISO, and other styles

43

Potma, Eric, Nicoletta Kahya, Wim P. de Boeij, and Douwe A. Wiersma. "A Multicolor Femtosecond Lightsource for (Multiphoton) Confocal Fluorescence Microscopy." Microscopy and Microanalysis 5, S2 (August 1999): 472–73. http://dx.doi.org/10.1017/s1431927600015683.

Full text

Abstract:

Recent advances in fluorescence microscopy add to the versatility of this optical technique and intensify its significance as an indispensable tool in biological research. Especially the use of multiphoton excitation offers the microscopist many advantages like inherent optical sectioning, reduced out-of-focus bleaching and higher penetration depths into the sample. In this regard, the commercial availability of pulsed solid-state lightsources like the Ti:Sapphire laser, that provide short pulses needed in the nonlinear multiphoton process, have paved the way for the routine implementation of multiphoton microscopy in the biologists laboratory. Although the spectral range of the commonly used Ti:Sapphire laser allows the application of two-photon fluorescence microscopy on chromophores that absorb in the range of 350-450 nm, a lasersource that enables the two-photon excitation of molecular probes at even shorter wavelengths (<350nm) would be highly beneficial.In this contribution we present a visible femtosecond optical parametric oscillator (OPO, Figure 1) that is ideally suited to excite molecular species at 285-335 nm by means of a two-photon process. Femtosecond pulses with durations as short as 30 fs can be generated within a tuning range from 570 to 670 nm. A cavity dumper incorporated in the laser cavity provides variable pulse repetition rates (single shot to 82 MHz).

APA, Harvard, Vancouver, ISO, and other styles

44

Tremblay, M. E., J. B. Simeonsson, B. W. Smith, and J. D. Winefordner. "Laser-Induced Double Resonance Ionic Fluorescence of Rare Earths in the Inductively Coupled Plasma." Applied Spectroscopy 42, no. 2 (February 1988): 281–85. http://dx.doi.org/10.1366/0003702884428185.

Full text

Abstract:

Laser excitation of ionic fluorescence overcomes the problem of spectral interferences encountered when trace analysis of the rare earths is performed by atomic/ionic emission spectrometry in the inductively coupled plasma. Two pulsed, excimer pumped, tunable dye lasers are used to excite ionic fluorescence of rare earths in an inductively coupled plasma. Since several fluorescence lines have been observed after laser excitation, it is possible to draw partial energy level diagrams for lanthanum, ytterbium, europium, and lutetium. Detection limits, linear dynamic ranges, and sensitivities are also reported. This is the first time that two-step excited fluorescence has been observed for any rare earths in an inductively coupled plasma.

APA, Harvard, Vancouver, ISO, and other styles

45

Ferrante, Carino, Alessandra Virga, Lara Benfatto, Miles Martinati, Domenico De Fazio, Ugo Sassi, Claudia Fasolato, et al. "Raman spectroscopy of graphene under ultrafast laser excitation." EPJ Web of Conferences 205 (2019): 05003. http://dx.doi.org/10.1051/epjconf/201920505003.

Full text

Abstract:

The out-of-equilibrium Raman response of graphene is addressed by pulsed laser excitation. Phonon spectrum is rationalized by revisiting the electron-phonon picture in the light of a transient broadening of the Dirac cone.

APA, Harvard, Vancouver, ISO, and other styles

46

Bagratashvili, V. N., M. V. Kuzmin, and V. S. Letokhov. "Kinetics of Nonequilibrium Gas Phase Reactions Induced by Vibrational Multiple-Photon IR Laser Excitation of Molecules." Laser Chemistry 7, no. 1 (January 1, 1987): 1–27. http://dx.doi.org/10.1155/lc.7.1.

Full text

Abstract:

A simple theoretical model for the qualitative description of the kinetics of the unimolecular decay in the pulsed IR laser field with strong deviation from thermal equilibrium is developed. The nonequilibrium character of the reaction is introduced by means of a special parameter of “truncation” of vibrational energy distribution function, which takes into account depletion of the distribution function due to the dissociation. The derived self-consistent system of differential equations describes the three dissociation regimes. Besides, the apparent cases of collisionless (short duration of laser pulse τp) and equilibrium (long τp) reactions, the intermediate collisional-nonequilibrium dissociation is revealed. The contribution of postpulse reaction has proved considerable in case of both long and short pulses. For the case of a successive dissociation the possibility of synthesis of labile products which cannot be produced at thermal initiation is established.

APA, Harvard, Vancouver, ISO, and other styles

47

Traeger, Georg A., Marlo H. Teichmann, Benjamin Schröder, and Martin Wenderoth. "Combining grating-coupled illumination and image recognition for stable and localized optical scanning tunneling microscopy." Review of Scientific Instruments 94, no. 2 (February 1, 2023): 023702. http://dx.doi.org/10.1063/5.0123604.

Full text

Abstract:

Combining scanning tunneling microscopy (STM) and optical excitation has been a major objective in STM for the last 30 years to study light–matter interactions on the atomic scale. The combination with modern pulsed laser systems even made it possible to achieve a temporal resolution down to the femtosecond regime. A promising approach toward a truly localized optical excitation is featured by nanofocusing via an optical antenna spatially separated from the tunnel junction. Until now, these experiments have been limited by thermal instabilities introduced by the laser. This paper presents a versatile solution to this problem by actively coupling the laser and STM, bypassing the vibration-isolation without compromising it. We utilize optical image recognition to monitor the position of the tunneling junction and compensate for any movement of the microscope relative to the laser setup with up to 10 Hz by adjusting the beamline. Our setup stabilizes the focus position with high precision (<1 μm) on long timescales (>1 h) and allows for high resolution STM under intense optical excitation with femtosecond pulses.

APA, Harvard, Vancouver, ISO, and other styles

48

Salmanov V. M., Guseinov A. G., Jafarov M. A., Mamedov R. M., and Mamedova T. A. "Features of photoconductivity and luminescence of CdS thin films and Cd-=SUB=-1-x-=/SUB=-Zn-=SUB=-x-=/SUB=-S solid solutions under laser excitation." Optics and Spectroscopy 130, no. 10 (2022): 1308. http://dx.doi.org/10.21883/eos.2022.10.54868.2983-22.

Full text

Abstract:

The features of photoconductivity and luminescence of CdS thin films and Cd1-xZnxS solid solutions obtained by chemical pulverization with subsequent pyrolysis under laser excitation have been studied experimentally. Pulsed liquid (473-547 nm) and nitrogen (337 nm) lasers were used as a radiation source. An experimental study was made of the photoconductivity and photoluminescence spectra of Cd1-xZnxS thin films depending on the composition x at different excitation intensities and the relaxation curves of nonequilibrium photoconductivity. It is shown that the observed features in the photoconductivity and photoluminescence spectra of Cd1-xZnxS thin films are due to direct band-to-band transitions. Amplification of light is observed at high intensities of optical excitation in thin CdS films. Keywords: Thin films CdS, Cd1-xZnxS, laser, photoconductivity spectra, photoluminescence

APA, Harvard, Vancouver, ISO, and other styles

49

Assefa, Tadesse A., Yue Cao, Soham Banerjee, Sungwon Kim, Dongjin Kim, Heemin Lee, Sunam Kim, et al. "Ultrafast x-ray diffraction study of melt-front dynamics in polycrystalline thin films." Science Advances 6, no. 3 (January 2020): eaax2445. http://dx.doi.org/10.1126/sciadv.aax2445.

Full text

Abstract:

Melting is a fundamental process of matter that is still not fully understood at the microscopic level. Here, we use time-resolved x-ray diffraction to examine the ultrafast melting of polycrystalline gold thin films using an optical laser pump followed by a delayed hard x-ray probe pulse. We observe the formation of an intermediate new diffraction peak, which we attribute to material trapped between the solid and melted states, that forms 50 ps after laser excitation and persists beyond 500 ps. The peak width grows rapidly for 50 ps and then narrows distinctly at longer time scales. We attribute this to a melting band originating from the grain boundaries and propagating into the grains. Our observation of this intermediate state has implications for the use of ultrafast lasers for ablation during pulsed laser deposition.

APA, Harvard, Vancouver, ISO, and other styles

50

Ballard, M. K., R. J. Hoobler, Chun He, L. P. Gold, R. A. Bernheim, and P. Bicchi. "Multiphoton LIF in atomic 6Li." Canadian Journal of Physics 72, no. 11-12 (November 1, 1994): 808–11. http://dx.doi.org/10.1139/p94-106.

Full text

Abstract:

The multiphoton laser-induced fluorescence excitation spectrum of 6Li vapor has been measured with a tunable, pulsed, nanosecond laser scanned between 13 600 and 14 500 cm−1. Two- and three-photon allowed excitation transitions originating from the 22S and 22P levels were observed, the latter likely originating from photodissociation products of Li2. Laser polarization and power dependencies are consistent with the multiphoton transition probabilities. Evidence for a parity "forbidden" multiphoton transition is also present.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Pulsed laser excitation'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles