ANGULAR BANDWIDTH FOR BRILLOUIN AMPLIFICATION

The angular bandwidth (ABW) of a Brillouin amplifier is shown to be de pendent on the spectral bandwidth of the interacting beams in a counte rpropagating geometry. Theory and experiment reveal that the actual AB W for typical lasers is much larger than monochromatic theory suggests . For single-longitudinal-mode pulses of a 8.5-ns duration interacting in CS2 the ABW is equal to +/-320 mrad (+/-18-degrees), corresponding to an external angle of +/-29-degrees. However, to permit us to take advantage of the full ABW afforded by the Brillouin interaction, prope r design of the amplifier is necessary to ensure that angular walk-off loss does not occur.