Abstract

Larson et al.¹ have recently reported studying the characteristics of a surface acoustic wave via optical scattering from a parallel ultrasonic setup in which the surface wave acts as a Raman-Nath grating and the scattering is controlled and monitored by a bulk (Bragg) grating placed adjacent to the surface wave. The acoustic frequencies are typically assumed to be simple harmonics or subharmonics, which may not always reflect a practical situation. An earlier study² had focused on the parallel ultrasonic problem from a multiple plane wave scattering perspective. In that study, simple harmonic frequency ratios were also assumed and both cells were chosen to be either at or near Raman-Nath. In this paper, we examine the diffraction effects associated with adjacent Raman-Nath and finite-Q Bragg cells (and their reverse order) in which the acoustic frequencies may be either simple harmonics or arbitrary. It is seen that analytical solutions are extremely difficult for the latter case, especially for a Raman-Nath/Bragg configuration. Numerical cases for variable $\widehat{\alpha }$ and δ values (where δ is an arbitrary phase factor between the cells) are examined in some detail.

© 1992 Optical Society of America