The diffractive characteristics at communication wavelengths of volume holographic gratings with the orthogonal readout scheme

In order to obtain good quality and high-dense wavelength division multiplexing (DWDM) devices,the diffraction property of volume holographic gratings, produced in an iron and indium co-doped LiNbO3 crystal by means of the transmission writing and orthogonal readout (TWOR) scheme,was analyzed theoretically and verified experimentally.The volume holographic grating with a grating size ratio of 1:1 was recorded at the laser wavelength of 532nm, and was successfully read out by using a tunable laser at the central wavelength around 1550nm.Correspondingly, the wavelength selectivity of 0.5nm was achieved, which was measured as the 3dB bandwidth of the diffraction efficiency curve.Meanwhile, the relationship of diffraction efficiency versus reading wavelength for such a volume holographic grating was obtained with the corrected solution to the 2-D coupled-wave equation in closed mathematical form.The experimental results agreed with the theoretical prediction well,and they show that the presented method is helpful for making a practical holographic grating DWDM device.