Intracavity optical birefringent filters

We propose, based on our recent investigations of a novel type of optical birefringent filter (called intracavity birefringent filter), a wavelength selective configuration, which may be used for Dense WDM applications. We show that this structure, formed with a classical Lyot-Öhman filter inside a ring cavity, takes the advantages of two typical filters: Fabry-Perot filters and birefringent filters, and in consequence gives a quite good compromise among usual filters parameters such as the working range, the bandwidth and the crosstalk. The theoretical considerations have been summarized. The first experimental results by use of a tunable nematic liquid-crystal light modulator have been shown.