Angular Spread of the Deflected Acoustic Beam Diffracted by a Bragg Grating Outof a Surface Acoustic Wave

摘要

In this paper, basing on the equations of the deflection angle and of thedeflection efficiency, the relation between the angular spread of the deflected SAW beam on the Bragg grating denoted by Delta-Theta sub 1 and the parameters of the grating is analyzed. A parameter referred to as Bragg width of the angular spectrum of the acoustic grating is defined and it is designated with Delta-Theta sub B. The meaning of the parameter Delta-Theta sub B for distinguishing the angular spread range of the deflection beam is discussed as well. It is concluded from the analysis that if the spread angle of the incident beam (labelled with Delta-Theta sub 1me) is larger than the Bragg width of the angular spectrum: of the grating, the spread angle of the deflection beam Delta-Theta sub 1 will equal to Delta-Theta sub m; On the contrary, if the angular divergency of the incident beam is less than Delta-Theta sub B, then, Delta-Theta sub 1 = Delta-Theta sub 1me. (MM).