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1.
The parameters of laser-pumped molecular lasers are investigated. It is established that the energy and tuning characteristics of an NH3 laser (Eg = 1.5 J, efficiency 20%, Pav = 20 W, radiation frequency tuning band 753–890 cm-1) are decisively influenced by the addition of N2. A focusing raster optical-pumping system has made it possible to obtain a specific lasing energy 12 J/liter. A CF4 laser with lasing energy 40 mJ operates in the 612–655 cm-1 band. Experiments on dissociation of the molecules CCl4 and UF6 were carried out with the aid of NH3 and CF4 lasers. The systems and methods of producing Raman lasers (RL) are presented. An effective RL amplifier on rotational transitions in compressed H2, which transforms tens of beams of Nd lasers into one coherent beam of the first Stokes component with λ ? 1.13 μm at an efficiencyup to 70%, is described.  相似文献   

2.
The GaCH3 radical has been directly detected by far UV laser mass spectrometry for the first time, as a UV laser photofragment from gaseous trimethylgallium Ga(CH3)3, but not from triethylgallium, Ga(C2H5)3. The relative yield Y() of GaCH3 was measured, at various UV photolysis laser wavelengths =193, 210 and 245 nm, and follows the absorption spectrum of the Ga(CH3)3 precursor molecules.  相似文献   

3.
Electrically pumped ultraviolet random lasing was achieved in metal-insulator-semiconductor (MIS) diodes based on ZnO films at room temperature. The ZnO films were grown by plasma assisted molecular beam epitaxy. Two different kinds of insulator layers, SiO x (0<x≤2) and AlO x (0<x≤1.5) were deposited by electron beam evaporation. X-ray diffraction experiments found these oxide layers were amorphous (or microcrystals), and X-ray photoelectron spectroscopy confirmed the Si and Al were fully oxidized. Compared with devices using SiO x as the insulator layer, diodes with evaporated AlO x layers showed a lower working threshold forward current (~20 mA to ~26 mA) and higher emission intensity. Periodic features indicating formation of closed-loop paths were deduced by the power Fourier transform of electroluminescence spectra. The cavity length of both devices increased as forward currents increased, while a larger cavity length was always obtained in the AlO x -involved device under the same working current. The improved performance was attributed to larger hole amount in AlO x layers. These results revealed that evaporated AlO x can serve as good electron blocking and hole supplying layers for hetero-structures.  相似文献   

4.
Photon echoes have been observed using a nitrogen laser pumped dye laser as the excitation source. The echo was obtained in the 3H43P0 transition in Pr3+:LaF3. The dependence of echoes on magnetic field and temperature was measured.  相似文献   

5.
High-order correction terms to the expression of the field of ultra-short tightly focused Gaussian laser pulses are derived. Terms up to seventh order in the small dimensionless spatial parameter s=1/(k0w00) and first order in the small dimensionless temporal parameter ε=1/(ω0t0) are explicitly presented (ω0=ck0 the central oscillatory frequency, 2t0 the pulse duration, w00 the beam waist radius at the central frequency ω0). To evaluate the correction efficacy, both the corrected and the paraxial field equations are used in detailed simulation studies of laser/electron interaction dynamics. Special attention is given to the vacuum laser acceleration scheme. The influence on the electron dynamics due to the diffraction edge field of a tightly focused laser beam is also investigated. PACS  42.25.Bs; 42.60.Jf; 41.75.Jv  相似文献   

6.
Femtosecond pulses were generated from a Cr4+: Cunyite laser using a combination of a broadband semiconductor saturable absorber mirror (SESAM), chirped mirrors, and passive mode locking. The astigmatically compensated asymmetric X-cavity with a 4.5-mm-long Cr4+:Ca2GeO4 sample was operated with a 2.5% output coupler. Dispersion compensation was achieved using chirped mirrors. During self-starting mode-locked operation, pulses as short as 365 fs were generated at a pulse repetition rate of 100 MHz with output power of 70 mW and a spectral bandwidth of 5.2 nm at the center wavelength of 1432 nm.  相似文献   

7.
The lack of sensitivity in far infrared of conventional modulation techniques can be overcome by the use of a laser beam as a powerful high resolution infrared source. As an illustration of these features we describe a thermoreflectance experiment performed on mercury telluride using a frequency stabilised CO2 laser. In this experiment a thin slab of HgTe was illuminated by the beam of the laser. A continuous shift of the Γ6v8c energy interval was produced by a slow temperature variation while the sample was submitted to a slight temperature modulation obtained by low frequency Joule heating. Synchronous and direct detection of the reflected beam gave the relative variation of reflectivity as a function of the sample temperature. Several spectra obtained at different emission lines enable us to determine the energy difference (Eg) between Γ6v and Γ8c inverted states. As a first approach a qualificative fit has been obtained with a simple model of dielectric constant and its temperature derivative. These results give the first direct determination of Eg near room temperature Eg = ? 117.04 meV at T = 286 ± 2 K.  相似文献   

8.
Ablation of polyetheretherketone (PEEK), a high temperature thermoplastic, by XeCl laser radiation occurs at fluences in excess of 0.07±0.01 J cm–2. The volatile products of ablation are CO and C2H2 with smaller quantities of CH4, C4H2, C6H6 and other C3 and C4 hydrocarbons. At fluences close to the threshold ablation produces involatile material of relatively high molecular weight but at high fluences extensive disruption of the PEEK structure occurs with conversion of all of the oxygen in the polymer to carbon monoxide.  相似文献   

9.
This article reviews the recent research on different types of planar and channel crystalline optical waveguides, fabrication methods such as liquid phase epitaxy, pulsed laser deposition, thermal bonding, reactive ion or ion beam etching, wet chemical etching, ion in-diffusion, proton exchange, ion beam implantation, and femtosecond laser writing, as well as waveguide laser operation of rare-earth and transition-metal ions in oxide crystalline materials such as Al2O3, Y3Al5O12, YAlO3, KY(WO4)2, and LiNbO3. To cite this article: M. Pollnau, Y.E. Romanyuk, C. R. Physique 8 (2007).  相似文献   

10.
At high temperature, the transmission peaks of a Fabry-Perot cavity filled with rubidium show sharp structures when the frequency of the laser is close to the 5S12 - 5D52 two-photon transition. These structures correspond to a laser emission between 5D52 and 5P32. The wavelength of this laser emission (7759 Å) is smaller than the exciting wavelength (7779 Å).  相似文献   

11.
A D2O laser has been developed for collective Thomson scattering measurements of ion temperature in high temperature plasmas. A pulse duration and a spectral width of a high power D2O laser has been successfully controlled for this purpose, by using a TEA CO2 laser injection-locked by an etalon-tuned TEA CO2 laser as a pump source.  相似文献   

12.
Three types of lasers (double-heterostructure 66 K InAsSb/InAsSbP laser diode, room temperature, multi quantum wells with distributed feedback (MQW with DFB) (GaInAsSb/AlGaAsSb based) diode laser and vertical cavity surface emitting lasers (VCSELs) (GaSb based) have been characterized using Fourier transform emission spectroscopy and compared. The photoacoustic technique was employed to determine the detection limit of formaldehyde (less than 1 ppmV) for the strongest absorption line of the v3 + v5 band in the emission region of the GaInAsSb/AlGaAsSb diode laser. The detection limit (less than 10 ppbV) of formaldehyde was achieved in the 2820 cm−1 spectral range in case of InAsSb/InAsSbP laser (fundamental bands of v1, v5). Laser sensitive detection (laser absorption together with high resolution Fourier transform infrared technique including direct laser linewidth measurement, infrared photoacoustic detection of neutral molecules (methane, form-aldehyde) is discussed.  相似文献   

13.
A transversely pumped far-infrared laser cavity has been used to discover two optically pumped laser lines: the 357.7 μm line from H2C=CF2 and the 242.3 μm line from CH3OH. Using heterodyne techniques, the frequencies of fourteen far-infrared laser emissions have been measured, six for the first time. PACS  07.57.Hm; 42.55.Lt; 42.62.Eh  相似文献   

14.
A laser magnetic resonance spectrometer has been used to discover and subsequently measure a far-infrared laser emission: the 166.6-micron line of CH2F2, optically pumped by the 9P24 CO2 laser. By recording spectra for the NH radical, the frequency of this laser emission has been determined to be 1799950±13 MHz. Spectra for the NH radical were also recorded with two other far-infrared laser emissions: the 160.4-micron line of N2H4 (9P46 CO2 pump) and the 328.6-micron line of 13CH3OH (9P12 CO2 pump). From the NH spectra, a discrepancy of 2.1 GHz with the previously measured laser frequency was identified for the 160.4-micron line. A three-laser heterodyne system was then used to remeasure the frequency to be 1868475.5±0.5 MHz. The NH spectra were also used to determine the frequency for the 328.6-micron line to be 912366±7 MHz, in agreement with the value previously calculated from the Rydberg–Ritz combination principle. PACS 07.57.Hm; 32.60.+i; 42.62.Eh  相似文献   

15.
All laser materials processing involves two fundamental phenomena: the conversion of optical energy into thermal energy, and the generation of thermal stresses in the laserprocessed materials. The distributions of the thermal energy and stresses in the substrate depend on the laser mode used for materials processing. A proper understanding of the temperature and stress distributions is essential for producing high-quality products using the laser technology. The solution of the complete thermoelastic problem is very complex and requires numerical methods. This paper presents simple analytic expressions for the temperature and thermal stress distributions in the substrate processed with TEM00 and TEM inf01 sup* mode laser beams. The temperature is found to be maximum at the point that encounters the maximum laser intensity. The thermal stress distributions are found to be different owing to the differences in the laser modes used for this study.  相似文献   

16.
We report here the operation of an optically-pumped multigas Far-IR laser. In our experiment, three different gases (CH3OH, CH3Br, CH3I) were simultaneously introduced into the Far-IR cavity. By adjusting the partial pressures of the gases and by tuning the appropriate CO2 laser pump line, we were able to obtain the laser action for each one of them as efficiently as is observed when the gases are present by themselves.  相似文献   

17.
It was shown both theoretically and experimentally that nanosecond order laser pulses at 10.6 micron wavelength were superior for driving the Sn plasma extreme ultraviolet (EUV) source for nano-lithography for the reasons of higher conversion efficiency, lower production of debris and higher average power levels obtainable in CO2 media without serious problems of beam distortions and nonlinear effects occurring in competing solid-state lasers at high intensities. The renewed interest in such pulse format, wavelength, repetition rates in excess of 50 kHz and average power levels in excess of 18 kiloWatt has sparked new opportunities for a matured multi-kiloWatt CO2 laser technology. The power demand of EUV source could be only satisfied by a Master-Oscillator-Power-Amplifier system configuration, leading to a development of a new type of hybrid pulsed CO2 laser employing a whole spectrum of CO2 technology, such as fast flow systems and diffusion-cooled planar waveguide lasers, and relatively recent quantum cascade lasers. In this paper we review briefly the history of relevant pulsed CO2 laser technology and the requirements for multi-kiloWatt CO2 laser, intended for the laser-produced plasma EUV source, and present our recent advances, such as novel solid-state seeded master oscillator and efficient multi-pass amplifiers built on planar waveguide CO2 lasers.  相似文献   

18.
An on-line cw dye laser multichannel spectrometer is described, which can be controlled by FORTRAN. Automatic tuning of a dye laser to the wavelength of maximum excitation selectivity for photochemical isotope separation is achieved. Applying the system to the selective photoaddition of iodine chloride ICl to acetylene, an enrichment factor of37Cl in the photoproduct C2H2ICl of β=100±5 was obtained. Both stable chlorine isotopes can be enriched to more than 97% purity in a single step, starting from natural samples in both cases.  相似文献   

19.
Aligned arrays of N2-encapsulated multilevel branched carbon nanotubes were synthesized using a simple one step CVD method by pyrolysis of ferrocene and acetonitrile. Electron energy loss spectroscopy (EELS) and elemental mapping studies reveal that gaseous nitrogen was encapsulated in the carbon nanotubes. Batch-type pyrolysis of catalysts induced flow fluctuation of the reaction gases, resulting in the growth of branched junctions. Molecular nitrogen extruded rapidly along conical catalyst particles inducing N2 encapsulation inside the branched nanotubes. PACS 07.78.+s; 61.46.+w; 81.07.De; 81.15.Gh  相似文献   

20.
A strong emission band extending from 3060 to 3120 Å was observed following proton beam excitation of an Ar-H2O mixture. This emission band was assigned to the transition of OH(A2Σ+)υ=0OH(X2Π)υ=0. At high argon partial pressure (> 200 torr), the precursor of this emission band is believed to be the argon excimer Ar2(1u). The fluorescence efficiency of Ar-H2O is estimated to be a factor of 4 times that of Ar-N2. Development of a highly efficient, tunable uv laser by e-beam pumping is promising.  相似文献   

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