All-optical wavelength demultiplexer with photorefractive grating array

Abstract

We propose an all-optical demultiplexer with grating array in a photorefractive crystal to achieve high density board-to-board optical interconnects with wavelength division multiplexing (WDM). WDM signal emitted from a board can be branched for each wavelength component and the components are connected to different spatial ports by this demultiplexer mounted on another board. Index gratings, which are induced by illumination of two control beams, are aligned spatially along the signal beam line in a photorefractive crystal. The wavelength component of WDM signal is diffracted by an index grating only when the phase-matching condition is satisfied. This condition is determined by incident angles of control beams and the wavelength of the signal beam. By setting incident angles of control beams appropriately, it can be determined whether a wavelength component of WDM signal is diffracted by the index grating or not. The component can be connected to the desirable output port by arraying the gratings with different grating vector. In our previous study, we have shown that this demultiplexer can branch WDM signal for each wavelength component. In this report, we show that the wavelength selectivity of 0.2nm can be achieved by optimizing the angles of input beams in this demultiplexer. Moreover, we propose a new system in which WDM signal is branched for each wavelength component by angularly multiplexed gratings. By using this multiple grating we can prevent demultiplexer module from growing in size with increasing the multiplicity of signal beam unlike grating array.