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Photo-induced degradation phenomena in strained ZnSe were investigated. (111) ZnSe substrates were bi-axially strained due to film deposition, and their cleaved (110) planes were exposed to a focused He–Cd laser for several thousands of seconds at room temperature. Although photoluminescence intensities decreased with the irradiation for all samples, the decreasing rates depended on the strains. Compressed regions degraded faster than diluted regions. No-strained regions degraded slower than the others. Conventional ZnSe based lasers have an active layer with compressive strains. Our results show that the laser with a diluted or no-strained active layer possibly survives longer.

Ultrasonic velocities of centrosymmetric KH3(SeO3)2 were measured along with additional measurements of the transition entropy and spontaneous strains. The ultrasonic velocity of the transverse wave with the wave number q//[010] and the polarization ε//[001] tends to approach nearly zero at the transition point (Tc) on approaching Tc from both sides of Tc. The basic experimental results are analyzed by a phenomenological theory and are discussed.

The ultrasonic velocity of the transverse wave with q= [010] and ξ = [001] measured as a function of temperature at 5 MHz in centrosymmetric KH3(SeO3)2shows a large anomaly with a tendency to approach zero at the transition temperature.