Stimulated Brillouin scattering of a KrF laser

A series of experiments in which the efficiency and fidelity of SBS (stimulated Brillouin scattering) wavefront reconstruction are measured as a function of the temporal coherence, focusing geometry, and power of the laser source is described. The primary motivation of the research is to assess the potential of SBS as the basis of a high-resolution image protection system. Thus, a series of high-resolution image projection experiments using a SBS mirror is also described. It is shown that provided that the coherent length of the laser is longer than the active focal region primarily responsible for the growth of the SBS wave, high SBS reflectivities can be obtained which are independent of the Rayleigh range of the focusing system used. In addition, wavefront reconstruction fidelities having values approaching unity can be observed when using laser powers near the threshold for the SBS process     

Stimulated Brillouin and Raman scattering for the generation ofshort excimer laser pulses

In this experimental work, the SBS and SRS processes were used in order to produce UV laser beams of good optical quality and short time duration. An XeCl oscillator and a double-pass amplifier with a phase-conjugate mirror via stimulated Brillouin scattering, generate the laser beam at 308 nm to pump a Raman cell. The oscillator pulse was 11 ns long, while the amplified phase-conjugate beam duration could vary from 3.3 to 1.5 ns, due to the compression operated by the Brillouin mirror. When this last laser beam was focused into a Raman cell containing methane at 30 atm, the shortest backward stimulated Raman scattering pulse at 338.4 nm was 170 ps long with 0.4 ml of energy. The 338.4-nm wavelength is interesting for the production of short bunches of cold electrons from Mg and Zn targets     

Stimulated Brillouin scattering of KrF laser radiation in dichlorodifluoromethane

Experimental measurements have been made of the stimulated Brillouin backscatter from CCl2F2gas in the range of pressures from 1 to 5.75 atm. Using narrow-linewidth KrF laser radiation as the pump backscatter efficiencies of up to 35 percent have been achieved, while at low backscatter efficiencies pulses as short as 1.5 ns in width were obtained.     

Extremely transient pulses from a Brillouin fiber laser

Stable trains of Stokes pulses with the unusually short duration of ≈200 ps were obtained, using a simple Brillouin fiber ring laser with standard single-mode, Ge-doped fiber. They were achieved by confining the fiber in the resonator, which resulted in reduced threshold and increased output power. This threshold reduction nontrivially allowed substantially shorter pump pulses (500-100 ps) to be used, and, as a result, extremely short Stokes pulses were generated     

宽带KrF激光抽运SF6受激布里渊散射的脉宽稳定性

从理论和实验上对利用宽带KrF激光抽运SF6产生的受激布里渊散射(SBS)的脉宽稳定性进行了研究。获得了受激布里渊散射脉宽稳定性随抽运功率密度稳定性、抽运脉宽稳定性及介质气压变化的规律。发现受激布里渊散射脉宽的稳定性与抽运激光的稳定性直接相关,抽运激光的稳定性越好,获得的受激布里渊散射脉宽相对稳定性也越好。抽运光脉宽和能量的不稳定都会造成所产生的受激布里渊散射脉宽不稳定。在较低抽运功率密度情况下抽运光脉宽和能量的波动对受激布里渊散射脉宽稳定性的影响都不可忽略,但在较高抽运功率密度情况下受激布里渊散射脉宽稳定性主要受抽运光脉宽波动的影响。对结果进行了分析和讨论,获得脉宽稳定性较好的受激布里渊散射输出的条件是,使用脉宽稳定性较好的抽运光和在保证没有其他非线性效应产生的情况下,尽可能提高抽运光的功率密度和介质气压。     

Subnanosecond pulses from a KrF laser pumped SF6Brillouin amplifier

Experimental measurements are presented of pulse compression in a backward Brillouin amplifier using SF6gas pumped by 0.9 GHz linewidth KrF laser radiation. Average pulse durations of 390 ps and energy extraction effieiencies of 40 percent from 24 ns pump pulses have been demonstrated at pressures of 15.3 and 12.6 atm, respectively.     

受激布里渊散射相位共轭镜在高功率纳秒激光器中的应用进展

受激布里渊散射(Stimulated Brillouin Scattering, SBS)是一种光学三阶非线性效应,其反射光具有相位共轭特性,在振幅、相位、偏振方面与入射光呈现时间反演关系,并保持与入射光相同的波前。在主振荡功率放大（Master Oscillator Power-Amplifier, MOPA）结构的纳秒激光器中,激光放大器中的热效应及光路中大量的光学元件使传输光束存在严重的波前畸变,在恶化光束质量的同时也限制了功率进一步提升的可能性。在此类激光器中使用基于受激布里渊散射的相位共轭镜(Stimulated Brillouin Scattering Phase Conjugate Mirror, SBS-PCM),使光束往返通过引入严重波前畸变的激光放大器能够实时补偿畸变,从而优化激光器的输出光束质量,并有利于功率的进一步提升,进而促进纳秒激光器向着兼顾高功率和高光束质量的方向发展,因此在高功率纳秒激光器中得到广泛应用。文中首先从理论方面简要介绍了SBS-PCM的基本原理及其相位共轭特性,其次对比了不同SBS-PCM介质的特点及适用范围,概述了国内外机构对SBS-PCM的研究进展及高功率纳秒激光器中SBS-PCM的典型应用情况及发展历程,并最终对SBS-PCM发展趋势进行了展望。     

Application of Brillouin diagram for a magnetized ferrite

The construction and the applications of the Brillouin diagram for a magnetized ferrite are discussed. It is pointed out that the application of the principle of limiting absorption for the determination of the proper solution in an unbounded ferrite is readily carried out with the help of the Brillouin diagram.     

Mechanisms of self-similar pulses generation in a normal dispersion-decreasing fiber

Based on the principle of virtual equivalent gain,the evolution of self-similar pulses in a normal dispersion-decreasing fiber is investigated.The occurrence of wave breaking during the process under highly nonlinear conditions and the effect of its revealed four-wave mixing on the process are also analyzed.The results indicate that the pulse spectrum broadeningin the initial stage is dominated by self-phase modulation while by four-wave mixing in the later stage.The more intense nonlinearity is,the faster the pulse evolution converges to the self-similarity synchronously in both the time domain and the spectrum domain.     

受激布里渊散射在ICF激光驱动器中的应用

本文概述了基于受激布里渊散射 (SBS)的位相共轭镜 (PCM )在惯性约束核聚变 (ICF)激光驱动器领域的实际应用 ,着重介绍了在高功率条件下 ,PCM的能量和功率负载强度、位相保真度和波形控制等关键问题。指出在超饱和工作条件下 ,采用SBS放大器—振荡器双池结构的PCM ,在获得高反射率、高保真度、可控脉冲输出的同时 ,不会增加激光系统的不稳定性。     

All-optical wavelength conversion of short pulses and NRZ signalsbased on a nonlinear optical loop mirror

Wavelength conversion of short pulses at 10 GHz based on a nonlinear optical loop mirror (NOLM) is experimentally and numerically investigated for the case of small group velocity dispersion and walkoff between the control pulses and continuous lightwaves. Experimental and numerical simulation results show that the pulsewidths of the converted signals at different wavelengths are almost the same, and the pulsewidths are compressed when the peak power of the control pulse is smaller than a certain value. An RZ optical source containing eight wavelengths having a high sidemode suppression ratio, equal amplitudes and almost the same pulsewidths is obtained by using wavelength conversion in a NOLM consisting of a common dispersion shifted fiber. 10 Gb/s NRZ wavelength conversion based on the NOLM is demonstrated for the first time and certain conclusions in some of the references are confirmed by our experimental results     

Sensitivity of phase-conjugate resonators to intracavity phase perturbations

The sensitivity of phase-conjugate resonators to phase perturbations is analyzed numerically. It is shown that as long as the phase-conjugate mirror (PCM) intercepts most of the light traveling towards it, this type of resonator provides much improvement over conventional optical cavities.     

Efficient generation of picosecond pulses at 243 nm

A new method is reported for generating tunable picosecond light pulses in the ultraviolet region of the spectrum. The system consists of a synchronously pumped mode-locked coumarin 102 dye laser which is mode-matched into an enhancement ring cavity with a mode spacing tuned to the repetition rate of the dye laser. A frequency modulation locking technique locks the carrier frequency of the mode-locked dye laser pulse train to the enhancement cavity. A beta-barium borate crystal was used to produce an average power of greater than 70 mW at 243 nm. There are many potential applications for this source, including the investigation of the 1S to 2S transition in atomic hydrogen using Doppler-free two-photon coherent multiple pulse spectroscopy     

All-optical generation of microwave and Millimeter wave using a two-frequency Bragg grating-based Brillouin fiber laser

A novel all-optical technique for microwave/millimeter-wave generation using two-frequency fiber Bragg grating (FBG)-based Brillouin fiber laser is presented. The mechanism for the microwave and millimeter-wave generation is theoretically analyzed. An approximately 33-GHz millimeter wave can be achieved through mixing the pump wave with the third Stokes' wave. In the experiment, an 11-GHz microwave signal is attained. The microwave frequency can be tuned by varying temperature of the fiber Fabry-Pe/spl acute/rot cavity of the Brillouin fiber laser. A more than 100-MHz tuning range around a frequency of 11 GHz is experimentally achieved.     

Simulation of the generation of ultrafast midinfrared laser pulses

A numerical simulation of an ultrafast semiconductor switch for 10.6 μm CO₂ radiation is presented. It is based on the solution of the Helmholtz electromagnetic wave equation for p-polarized light and the ambipolar diffusion equation. Calculations are performed in various time dependent inhomogeneous plasma profiles. The analysis shows that the temporal reflectivity depends on the initial visible radiation fluence, duration, and diffusion coefficient of the sample. The results support the feasibility of generating midinfrared ultrashort pulses between 100 fs and 65 ps. By proper choice of the laser fluence and the semiconductor material, longer pulses are also possible     

New method for generation of coherent ultrashort optical pulses

A new method for generating coherent ultrashort optical pulses from semiconductor lasers with GRIN short external coupled cavity (GSCCL) by means of sinusoidal direct modulation is proposed. 20 ps coherent ultrashort optical pulses have been obtained; the repetition rate is 730 MHz, and the side mode suppression ratio is more than 35 dB.<>     

基于分布增益非线性光纤环镜的弱脉冲放大与压缩

已有研究发现,用分布增益非线性光纤环镜放大和压缩超短光孤子不仅能避免常规掺铒光纤放大器中由于非线性效应引起的孤子崎变,而且可克服绝热放大技术放大器长度随输入脉宽增大而指数规律增大的困难。我们进一步计算了弱脉冲在分布增益非线性光纤环镜中的放大和压缩过程。结果表明,对于峰值功率比基阶孤子低得多的弱脉冲输入,用分布增益非线性光纤环镜同样可实现无崎变的脉冲能量放大和脉宽压缩;而且,经环镜放大输出的脉冲也接近基阶孤子。然而,输入脉冲峰值功率越低,实现最佳放大所需的环镜总增益越大,高阶效应对放大结果的影响越显著。     

Multiple-short-pulse stimulated Brillouin scattering for trains of200 ps pulses at 1.06 μm

High-reflectivity, good-fidelity multiple-short-pulse stimulated Brillouin scattering phase conjugation is demonstrated for pulse trains containing pulses of 200-ps duration with interpulse separations of 7.5 ns. The reflectivity is seen to build up from pulse to pulse to a final value of 52%. The Brillouin medium is high-pressure SF₆ gas having a Brillouin lifetime of 35 ns. Severe competition with optical breakdown is discussed     

Effective generation of tunable single- and multiwavelength optical pulses from a Fabry-Perot laser diode

A tunable pulse source capable of both single- and multiwavelength oscillations has been developed by self-injection seeding of a laser diode. A side-mode-suppression ratio (SMSR) of about 20 dB has been obtained in the outputs. The key element in our setup is a wavelength multiplying stage consisting simply of 50/50 beam splitters, a diffraction grating, and a mirror. The maximum number of available wavelengths increases rapidly with the beam splitters. Our scheme can be adopted for use in high-speed wavelength switching.     

High bit rate characteristics of short pump pulses generated by stimulated Brillouin scattering in optical fibres

A new method for generating optical pulses is demonstrated experimentally. The pulses are created from a phase modulated CW signal which is propagated through an optical fibre under the influence of stimulated Brillouin scattering. Repetition rates much larger than the Brillouin linewidth have been achieved.<>