Birefringent computer-generated holograms are fabricated in bulk fused silica by tight focusing of infrared femtosecond laser pulses. The polarization properties of the elliptically polarized diffracted light are in excellent agreement with the theoretical model. We experimentally demonstrate that for such birefringent structures the signal-to-noise ratio increases by approximately 9 dB when polarization filtering is used to suppress the undiffracted beam.