The aim is to develop a rapid and direct method for measuring the bulk viscosity of a liquid as a function of temperature. Brillouin scattering of a laser beam in fresh water and salt water at different temperatures has been studied. The results show that there exists a close temperature-dependent relationship among the Brillouin frequency shift, the Brillouin linewidth, and the bulk viscosity of water. Thus the bulk viscosity of water can be determined directly from Brillouin-scattering measurements. The method has a high signal-to-noise ratio and high accuracy.

It is reported experimentally that low-threshold random lasing in a weakly scattering disordered structure formed by speckles using holography is achieved. It shows that the emission property of the structure is related directly to the pulse duration of the pump laser. If pumped by picosecond pulses, several spikes are observed in the emission. If pumped by a nanosecond laser, only a single dominant peak appears. The wavelength tunability of the random laser with a change in temperature has been demonstrated. The corresponding physical analyses have also been provided briefly.

A new method for accurate measurement of the threshold value of stimulated Brillouin scattering (SBS) in water in terms of pump laser intensity is investigated. The threshold value of SBS is determined by the point of the deviation of the value of the attenuation coefficients of wide- and narrow-linewidth lasers rather than the intensity of the backscattered SBS signal in the material.