Thermally tunable 100GHz spaced four-wavelength electro-optic filter based on aperiodically poled lithium niobate

We propose theoretically a method for designing a narrowband multi-wavelength. Solc-type filter based on the linear electro-optic effect in aperiodically poled lithium niobate. As one of its applications we demonstrate a thermally tuned 100 GHz spaced four-wavelength filter, whose working electric field is only 0.219 kV mm(-1) in an 8 cm long crystal. The filter allows four wavelengths to pass simultaneously with a 3 dB bandwidth of 0.26 nm, a passband of 32.5 GHz and a channel isolation of more than 8 dB, which can be tuned by temperature in a wide range at a rate of -0.69 nm degrees C-1. It is found that the domain errors of the aperiodically poled lithium niobate crystal within 25% are beneficial to the performance of the filter. The filter will be useful for dense wavelength division multiplexing optical communication systems.