Holographic transmission grating for use in the 1250-1600 nm fibre window

Wavelength division multiplexing (WDM) has been suggested for use in fibre optic based local area networks. For large numbers of channels, grating based devices offer the most efficient means of multiplexing. Since it may be undesirable to control the polarisation state of signals on such a network, polarisation insensitive multiplexers could be advantageous. The use of volume transmission gratings in a multiplexer can offer significant advantages over surface relief gratings in terms of efficiency and uniformity of response to different polarizations. The authors describe a volume transmission grating for use in a wavelength division multiplexer in 1250-1600 nm window. The design and fabrication of the grating is described and experimental results are presented for its performance in both polarisations at wavelengths across the operating window. These results are compared with the performance of a conventional blazed diffraction grating