In our work on the amplification of Bleustein‐Gulyaev waves in
photoconducting CdS crystals, we have found that the gain as a
function of electric field is quite symmetric about the
synchronous value. We have therefore been able to achieve
amplification with a segmented structure consisting of an
interdigital electrode. The unequal spacing between fingers
produces amplification in the region where the field is
positive, which is in excess of the attenuation in the region
where the field is negative. The spacings between adjacent
electrodes are 500 and 250 μm, giving a periodicity of 850 μm;
the length of the active region is 6 mm. The experimental
electronic gains obtained were 19 dB at 43 MHz and 32 dB at 86
MHz with an applied voltage of 130 V; 4 dB net gain was obtained
at 86 MHz. It has been observed that the electronic gain is
sensitive to the photoexciting light wavelength. We give an
interpretation of this phenomenon based on the relative
penetration depth of the mechanical wave, of the photoexcited ca