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Tunable optical filter for wavelength division multiplexing using photorefractive planar waveguide

In this paper, we propose a tunable optical filter using a photorefractive planar waveguide. The index grating generated by the control beam drops off a part of wavelength components in the wavelength division multiplexed signal beam. It make possible to select the wavelength components of the signal beam by optically adjusting the wave vector of the grating. The photorefractive effect is one of the most efficient nonlinear effects, and therefore the signal beam can be controlled by the relative low beam power. The proposed optical filter can be applied to an active add-drop module when the signal beam is fed back to the module as a control beam. Therefore, it contribute to development of the all-optical network systems. It is also able to apply to photonic label processing technology by multiplexing the index gratings. We investigated the signal beam propagation and the permittivity distribution in the photorefractive waveguide by using a finite dimensional beam propagation method (FD-BPM) and analyzed the filtering property. Considering the two optical setups using the transmission and reflection grating, we compared these performances.