ADDITIONAL PHASE-SHIFTS IN ULTRASOUND LIGHT-DIFFRACTION

Additional optical phase shifts in ultrasound light diffraction are in vestigated both numerically and experimentally. Whilst these phase shi fts are negligible when the weak acousto-optic interaction (Raman-Nath regime) is considered they play an essential role in a strong acousto -optic interaction. Owing to their particular properties the additiona l phase shifts can be distinguished in the initial phase, which exists even when there are very small variations of the refractive index (Ra man-Nath parameter), and the v-dependent phase shift which depends on the maximum variation of the refractive index. Both of these effects a re of great importance when the interaction between diffraction orders is considered, for example in the case of quantitative sound field in vestigations or the development of acousto-optic devices.