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This paper gives out two kinds of novel well-behaved stimulated Brillouin scattering (SBS) mediums, FC-3283 and FC-770. Numerical calculation and experimental measurements show these two mediums both having lower absorption, higher optical loads and short phonon lifetime, which making them good candidate mediums for high-energy high-power SBS. Using them as the mediums in the compacted two-cell SBS phase-conjugation mirror, it is easily to generate ultrashort phased-conjugated Stokes pulses just with hundreds picoseconds. When the incident light energy is beyond 200 mJ, the pulse width of 8 ns can be compressed to 200 ps or less in both mediums. Especially, the FC-770 is very suitable to be chosen for generating the SBS picosecond pulses with the narrowest compression pulse width of 109 ps and the highest energy reflectivity of 80%.

The effect of smoothing by spectral dispersion (SSD) on stimulated rotational Raman scattering (SRRS) in air has been investigated both numerically and theoretically. The suppression effect of SSD on SRRS process is verified and it is demonstrated and proposed that the suppression effect is attributed to two aspects: the decreasing of the laser fluence modulation degree and the reducing of Stokes gain coefficient caused by the temporal and spatial variation of the phase of the incident laser pulse. The simulation results show that the SRRS threshold distance can be lengthened by choosing appropriate SSD parameters.

In this paper, we designed an experiment to research the properties for the stimulated Brillouin scattering (SBS) medium of perfluorocarbon-compounds (PFCs) and perfluoropolyether (PFPE), then we proposed that the selection principle of the high load capacity SBS medium can be used in the high peak power SBS system. The results showed that, for PFCs, perfluorinated hydrocarbons (FC-72) has the highest optical breakdown threshold (OBT); for PFPE, the medium with average molecular weight (AMW) less than 1000 has small medium absorption coefficient (AC) and high OBT, for AMW, greater than 1000, the medium AC becomes high and the OBT becomes low. Further research shows that, for PFPE series SBS medium, the AC increases and the OBT decreases gradually with increasing of AMW. We find some SBS mediums can work stably under high peak power pump, which lays a good foundation for the application of SBS technology in a high-power laser system.

The current trends in stimulated Brillouin scattering and optical phase conjugation are overviewed. This report is formed by the selected papers presented in the “Fifth International Workshop on stimulated Brillouin scattering and phase conjugation 2010” in Japan. The nonlinear properties of phase conjugation based on stimulated Brillouin scattering and photo-refraction can compensate phase distortions in the high power laser systems, and they will also open up potentially novel laser technologies, e.g., phase stabilization, beam combination, pulse compression, ultrafast pulse shaping, and arbitrary waveform generation.

A new approach to measure stimulated Brillouin scattering threshold based on the output energy characteristic of stimulated Brillouin scattering optical limiting is proposed. The stimulated Brillouin scattering threshold or its exponential gain, Gth, can be accurately and conveniently determined by the intersection point of linear-fitting lines of the output energy below and above the threshold. The values of Gth in CS2 and FC-72 for different wavelengths and interaction lengths are measured in Continuum's Nd:YAG Q-switched laser and its frequency-doubled system. We show that Gth for transient regime is larger than that for steady state, and increases with the pump wavelength and the interaction length.

The effect of medium temperature upon characteristic of stimulated Brillouin scattering (SBS) and SBS optical limiting is investigated. The physical mechanism behind is analyzed theoretically and experimentally verified in Continuum's Nd: YAG Q-switched laser system using FC-72 as the SBS medium. The temperature affects the electrostrictive coefficient, refractive index, density and acoustic velocity of the medium weakly. In contrast, the kinematic viscosity, which is inversely proportional to the temperature, is related to gain coefficient and phonon lifetime and thus greatly affects the SBS characteristics. Therefore, in the low temperature, the kinematic viscosity is usually high, which can lead to a small gain coefficient and a short phonon lifetime. Therefore, the SBS characteristic can be changed by controlling the temperature to a great extent.

In order to improve the optical limiting performance based on stimulated Brillouin scattering (SBS), a combination of SBS and carbon nanotube/HT-270 suspension for optical limiting is proposed in this paper. The dependence of output energy of optical limiting based on this hybrid approach on the pump energy is numerically simulated, and validated in Continuum's Nd: YAG seed-injected laser. The results indicate that the output energy based on this hybrid approach shows much better performance compared with that based on single SBS. In this approach, the SBS threshold can be controlled by adjusting the gain coefficient of medium and focal length of the lens, and the threshold of suspension can be controlled by altering the concentration and focal length of the lens, therefore, this hybrid approach to realize optical limiting has great potential in practical application.

We will theoretically and experimentally study the effect of the linewidth and the frequency of a weak detuned signal on its amplified spectrum in the Brillouin amplifier. We will show that the spectral profile of the input signal is preserved during amplification only when the signal linewidth is much narrower than the Brillouin linewidth of the amplifier. If the signal linewidth is near or above the Brillouin linewidth, the frequency shift of the amplified signal with respect to the pump will be close to the Brillouin shift of the amplifier, and will be independent of the frequency shift of the input signal.

A method of generating flat-top waveform in the time-domain based on stimulated Brillouin scattering (SBS) using medium with short phonon lifetime is proposed. In theory, the transmitted pulse is simulated in the case of several media with different phonon lifetime. In experiment, FC-72 and HT-270, which differ significantly in the phonon lifetime, are exploited in the experiment. Both the theoretical and experimental results indicate that, when choosing medium with short phonon lifetime, the top is almost a platform, while there is a peak in the front and a platform thereafter when choosing medium with long phonon lifetime.

In order to enhance the power-load of two-cell stimulated Brillouin scattering (SBS) system, methods of using different media and mixed medium are proposed. In theory, the amplification function of two-cell system of different medium with close vicinity in the Brillouin frequency shift (BFS) is analyzed. Also the variation of BFS of the mixed medium with the mixing ratio is analyzed. In the two-cell SBS system pumped by Q-switched Nd:YAG laser, the SBS system performance characteristics are investigated with different media and mixed medium. The experimental results indicate that the Stokes can be sufficiently amplified by choosing different medium with close vicinity in the BFS; the power-load performance is enhanced as well as the maximum amplification efficiency the Stokes by choosing mixed medium.