Optical bandpass Lyot filter with tunable bandwidth

We experimentally demonstrate the feasibility of the bandwidth tuning of a liquid-crystal based bandpass Lyot filter. This bandwidth tuning is achieved by applying a voltage to vary the birefringence of the liquid-crystal cells whose optical path difference takes predefined discrete values. We show that for a 2-stage liquid-crystal Lyot filter and at λ_i = 1.543 μm, the measured 3-dB bandwidth varies from 17 nm to 60 nm when the applied voltage increases from 0 V to 5.24 V. The shape of the transmission response remains unchanged during the bandwidth tuning process.