Bragg-selectivity of a volume gain grating

We adapt the theory of volume grating holography to model analytically the diffraction efficiency of a volume gain grating and its variation due to deviation from Bragg-matching, We present modelling of the case when the gain grating is optically-written in a saturable laser amplifier by spatial hole burning, under both steady-state and transient conditions. We perform an experimental measurement of the angular-sensitivity of a volume transmission gain grating optically-written in a Nd:YAG amplifier rod. It is shown that the amplification of the writing beams needs to be considered since this leads to a spatial variation of the grating modulation depth and thereby to the reduction of its angular sensitivity compared to the uniform grating case.