Gaussian apodized volume grating to suppress the crosstalk in holographic demultiplexers using high-efficiency photopolymers

A Gaussian apodization technique applied to a transmission volume hologram for a holographic demultiplexer is proposed. A Gaussian apodized grating 15×11 mm in size, 38 µm thick, and with a 3.2-mm horizontal standard deviation of the modulating index profile is fabricated. A 22-channel demultiplexer based on that grating has been optically demonstrated. Channel spacing, interchannel crosstalk level, and channel uniformity of 0.8 nm, –30 dB, and 1.5 dB, respectively, are obtained. In addition, an insertion loss of 13 dB, which is caused by the primary limitation of this technique, is observed.