Acoustic absorber having a roughened surface for ao devices

A method of surface texturing of an acousto-optic (AO) device, comprising:

• calculating at least a first spatial frequency based on (i) a wavelengths of bulk acoustic waves (BAWs) (BAW wavelength) to be used in operating said AO device including an AO crystal comprising a plurality of faces including a first face and a second face, and an input transducer having an electrode bonded to said first face (top electrode) for receiving an RF signal and launching bulk acoustic waves (BAWs) configured to interact with an optical beam propagating in said AO crystal, wherein said BAWs are received at least in part by said second face after said interacting with said optical beam, and
• texturing said second face so that said second face has a roughened surface portion over an area of at least (≧) 50% of an area of said top electrode, and a root mean square (rms) surface roughness of at least (≧) 1 μm and a periodicity having at least a first spatial frequency peak when expressed as a feature period being from 0.5 to 2.0 times said BAW wavelength.