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1.
The influence of the ellipticity degree of the pump radiation polarization on threshold energies and energy conversion efficiencies of stimulated rotational Raman scattering (SRRS) are investigated in H2 with a XeCl excimer laser, by using different focusing geometries. For the first time, it is shown that the dependence of SRRS on pump radiation polarization is also affected by the focusing geometry, i.e. whether low- or high-angle focusing is applied. The experimentally determined threshold energies as a function of the pump radiation polarization are in accordance with theory mainly at high-angle focusing geometries. It is also shown for the first time that gain suppression effects on vibrational Raman scattering have to be considered in understanding the experimental results. Received: 5 January 1999 / Final version: 10 September 1999 / Published online: 8 March 2000  相似文献   

2.
An XeCl laser beam has been used to investigate stimulated Raman scattering in H2 and in various H2-foreign gas mixtures. Helium, neon, argon, and nitrogen have been tested as foreign gases. In all the investigated mixtures with 50% of H2, the energy conversion efficiency to the first Stokes (353 nm) was more than 70% higher than that obtained in H2 at the same total pressure (40 bar) and pump energy (60 mJ). The dependence of the energy conversion efficiency on pump beam divergence has also been investigated.  相似文献   

3.
Radiation at 2.36 μm is produced by stimulated electronic Raman scattering in barium vapour. The pump radiation is provided by a XeCl excimer laser. Photon conversion efficiencies of up to 1% are observed. The variations of the infra-red Stokes output with barium number density and with pump intensity are described.  相似文献   

4.
Experimental results on the generation of 1.54 μm eye-safe radiation in pure CH4, CH4:He and CH4:Ar mixtures pumped by the fundamental of an Nd:YAG laser, using the stimulated Raman scattering (SRS) technique, are described. A decrease in the energy conversion efficiency and degradation in the beam quality of S1 was observed in pure CH4 at high pump energies. This problem was overcome in CH4:He and CH4:Ar mixtures. Compared with the first Stokes (1.54 μm) energy conversion efficiency in pure CH4, at a pump energy of 126 mJ, an enhancement of 50% in energy conversion efficiency was observed in the CH4:Ar mixture (60% argon concentration) and as much as 100% in the CH4:He mixture (60% helium concentration). The use of these buffer gas mixtures improved the spatial beam quality of the Stokes radiation considerably and also resulted in raising the pump threshold for optical breakdown of the Raman gain medium.  相似文献   

5.
Experimental results on the generation of 1.54 μm eye-safe radiation in pure CH4, CH4:He and CH4:Ar mixtures pumped by the fundamental of an Nd:YAG laser, using the stimulated Raman scattering (SRS) technique, are described. A decrease in the energy conversion efficiency and degradation in the beam quality of S1 was observed in pure CH4 at high pump energies. This problem was overcome in CH4:He and CH4:Ar mixtures. Compared with the first Stokes (1.54 μm) energy conversion efficiency in pure CH4, at a pump energy of 126 mJ, an enhancement of 50% in energy conversion efficiency was observed in the CH4:Ar mixture (60% argon concentration) and as much as 100% in the CH4:He mixture (60% helium concentration). The use of these buffer gas mixtures improved the spatial beam quality of the Stokes radiation considerably and also resulted in raising the pump threshold for optical breakdown of the Raman gain medium.  相似文献   

6.
A high-powered tunable terahertz wave (THz-wave) has been parametrically generated via a surface-emitted THz-wave parametric oscillator (TPO) pumped by a multi-longitudinal-mode Q-switched Nd:YAG laser. The effective parametric gain length was enlarged by employing two MgO:LiNbO3 crystals. The tunable THz-wave radiation from 0.8 to 2.8 THz was realized via varying phase-matching angle between the pump wave and the Stokes wave. The maximum THz-wave radiation was 173.9 nJ/pulse at 1.7 THz as the pump energy was 82 mJ, corresponding to an energy conversion efficiency of about 2.12 × 10−6 and a photon conversion efficiency of about 0.035%. The first-order, the second-order and the third-order Stokes waves were observed during the experiments.  相似文献   

7.
A simple combination of a lens-based unstable resonator and an inverted telescope coupling geometry working in a XeCl laser pumped H2 Raman cell are presented. Raman spectrum optimization is achieved by varying the pump beam numerical aperture. 70% pump depletion and energy conversion efficiencies as high as 66% and 7.8% have been obtained for S1, S2 and S3 respectively.  相似文献   

8.
16-μm Stokes pulses were directly generated for the first time to our knowledge by an intracavity configuration for the para-hydrogen Raman laser. We have analyzed Stokes field growth using a focused gain model and designed a pump/Stokes cavity to satisfy CO2 pump power and pulse duration requirements for Raman oscillation. The CO2 laser oscillation with circular polarization was realized by seeding externally circularly polarized CO2 radiation. An output energy of 2.4 mJ was obtained with the output coupler of 0.5% transmittance, which indicated that 420 mJ of Stokes pulse energy was stored inside the cavity. This suggests that a much higher energy can be extracted by the optimization of cavity parameters. Received: 18 November 1998 / Published online: 26 May 1999  相似文献   

9.
The radiation transfer equations of the extracavity Raman laser including up to the third Stokes beams and backward Raman scattering terms were deduced in detail from the wave equation and material equations of stimulated Raman scattering. The radiation transfer equations were solved numerically to optimize the performance of the extracavity Raman lasers with barium nitrate crystal as the nonlinear medium. The optimum reflectivity of the output coupler at the first Stokes was figured out numerically to achieve the maximum conversion efficiency of the first Stokes, and found to be closely related to the pump pulse duration, peak intensity of the pump pulse, and Raman crystal length. With the resonator mirrors highly reflective at the first Stokes, the highest conversion efficiency of the second Stokes was obtained when the input mirror was highly reflective at second Stokes, whereas the output coupler was highly transmissive at the second Stokes. It was found that too high intracavity intensity of the second Stokes would impede the efficient energy extraction from the pump pulse to the first Stokes, and consequently, limit the conversion efficiency of the second Stokes.  相似文献   

10.
Fifth harmonic conversion of radiation from a XeCl laser in Ar and Kr, generating radiation at 61.6 nm, is reported. Fifth power law variation of the generated energy with the pump energy is observed. The effects of continuum absorption are observed in the width of the phase matching peak in Ar.  相似文献   

11.
Continuous-wave operation of a diode-pumped Nd:YVO4 laser with self-frequency Raman conversion is demonstrated. The threshold of Raman generation was measured to be 1.3 W of laser diode power. The maximum output power of Stokes radiation at the wavelength of 1177 nm was up to 50 mW at a laser diode pump power of 2.3 W, corresponding to the slope efficiency of 5%. The beam quality M2 of the Stokes radiation was about 1.4. The fluctuations of the Stokes power were minimised down to 4%. PACS 42.55.Ye; 42.60.Pk; 42.65.Dr  相似文献   

12.
A high-temporal contrast femtosecond Stokes pulse near 1,053 nm is obtained simply without polarizer extinction ratio limitation based on the stimulated Raman frequency shift process in ethanol with an 800-nm femtosecond Ti:sapphire laser as a pump source. By optimizing the incident pump pulse chirp and the ethanol Raman cell length, a clean Stokes pulse near 1,053 nm with a maximum energy of 0.24 mJ is obtained with ~7.5 % conversion efficiency and 0.8 % (rms) energy fluctuation. Compared with the incident pump pulse, the temporal contrast of the Stokes pulse is improved by at least approximately three orders of magnitude.  相似文献   

13.
Sub-nanosecond microchip laser with intracavity Raman conversion   总被引:3,自引:0,他引:3  
Efficient sub-nanosecond pulse operation of microchip lasers with intracavity Raman conversion and pulse compression is presented for the first time. The microchip lasers were composed of Nd:LSB or Nd:YAG laser crystals, Cr4+:YAG saturable absorber, and Ba(NO3)2 Raman medium. The pulse duration obtained at the Stokes wavelength (1196 nm) was as short as 118 ps. Optical conversion efficiency of laser-diode pump power to the Stokes power of 8% was reached. Pulse energy and peak power of Stokes emission were 1.2 μJ and 5.4 kW, correspondingly. Numerical calculations are in good agreement with obtained experimental results. Received: 20 December 2002 / Revised version: 6 March 2003 / Published online: 5 May 2003 RID="*" ID="*"Corresponding author. Fax: +1-716/645-6945, E-mail: ankuzmin@acsu.buffalo.edu RID="**" ID="**"Present address: University at Buffalo, SUNY, The Institute for Lasers, Photonics, and Biophotonics, 458 NSC, Buffalo, NY 14 260-3000, USA  相似文献   

14.
We demonstrated the growth profile of stimulated Raman anti‐Stokes scattering (SRS) of carbon disulfide (CS2) influenced by fluorescence seeding of all‐trans‐β‐carotene and rhodamine‐B (RhB) in liquid‐core optical fiber (LCOF). The pump energy which was needed to build up the first‐order anti‐Stokes radiation of CS2 solutions with the fluorescence seeding was lower than that of CS2 solutions without fluorescence seeding because of the fluorescence enhancement effect on the intensity of the first‐order Stokes radiation. The first‐order anti‐Stokes radiation of the RhB solution (10−8 M ) was built up at a lower pump energy than that of the all‐trans‐β‐carotene solution (10−6 M ), and the intensity of the first‐order anti‐Stokes radiation of the RhB solution was higher than that of the all‐trans‐β‐carotene solution. Simultaneously, the coupled wave differential equations were obtained by the theoretical derivation, and the growth profile of the first‐order anti‐Stokes radiation was theoretically calculated with and without the fluorescence seeding by these equations. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

15.
Energy output of 400 mJ, an order of magnitude higher than reported previously is obtained in aQ-switched flashlamp-pumped Nd3+:KGd(WO4)2 laser. No pronounced saturation of the output energy with respect to the pump energy is observed. Multiwavelength operation due to efficient Stokes conversion in the laser crystal is demonstrated.  相似文献   

16.
A multilens high pressure H2 cell has been used to demonstrate that efficient, high optical quality and low threshold down-conversion to 1st Stokes can be obtained also with a poor quality broadband pump, with just the condition that the pump pulsewidth is larger than the cell transit time. A backward 1st Stokes with 0.7 overall quantum efficiency conversion has been obtained from a broadband Nd:YAG duplicated laser.  相似文献   

17.
The lasing properties of an intracavity Nd:KGW Raman laser which converts the multimode radiation of an Nd:KGW laser operating on the 4 F 3/24 I 11/2 transition into the third Stokes component at a wavelength of 1.5 μm are studied. The energy in the third Stokes component is found to increase essentially linearly with the electrical energy delivered to the flashlamp. Lasing at the third Stokes component begins in the central portion of the Nd:KGW crystal and then propagates to its boundaries. Reducing the geometric aperture of the multimode pump beam in the Raman crystal lowers the divergence of the Stokes emission. For a source pump energy of 6 J, the intracavity Raman laser emits 14.7 mJ pulses of duration 3–4 nsec which are safe to the eyes. The divergence of the Raman laser beam at a level of 86% of the total energy is ≈ 9 mrad.  相似文献   

18.
本文采用Raman-Maxwell-Bloch方程,计算了宽频带聚焦泵浦准稳态受激电子喇曼散射的增益因子和能量转换效率.在计算中考虑了泵浦抽空、喇曼介质对泵浦光的吸收和喇曼介质的泡和效应.计算结果与XeCl激光在钡蒸汽中的受激喇曼散射实验基本上符合.  相似文献   

19.
Spectral luminescent properties of eight organic dyes are studied upon excitation by focused radiation from the XeCl* laser at the pump power up to 200 MW/cm2. The transmission of pump radiation by dyes is investigated as a function of the pump power. It is shown that variations in the energy, spectral, and temporal parameters of radiation of organic dyes upon high-power excitation are explained by the development of superluminescence (amplified spontaneous emission).  相似文献   

20.
High-efficiency frequency conversion in H2 of a nitrogen laser oscillator-amplifier system is described. The laser system provides about 1 MW output power with a very low intrinsic divergence. Up to 3 Stokes lines at 392, 468, and 581 nm and 3 Anti-Stokes at 296, 263, and 237 nm, respectively, have been observed at the output of the 60 cm long H2 Raman cell. Peak power values of 500, 300, and 70 kW have been measured for the first 3 Stokes, respectively, corresponding to a 56% pump energy conversion efficiency.A comparison between free and guided propagation (in a hollow dielectric waveguide) is also reported, for various values of the pump intrinsic divergence.  相似文献   

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