Temperature properties of laser-induced interference filters in lithium niobate

The temperature properties of subangström bandwidth interference filters written in photorefractive lithium niobate crystals are investigated. The temperature sensitivity of the center wavelength is described with a theoretical model based on the phase matching condition. The theory is compared favorably with our experimental results, on unfixed filters at 413 nm and 514.5 nm, and with the work of other groups. A sensitivity of 0.047 Å/K and 0.104 Å/K are measured for filters with the grating wave vector, respectively, parallel and perpendicular to the c-axis. Using a novel method the spectral response is deduced from combined angular and temperature response measurements. An asymmetry is observed in the filter response. A spectral bandwidth of 0.05 Å is estimated for a filter with a measured thermal bandwidth of 0.5 K, giving a temperature tuning range of 2 Å and a stabilization accuracy of 0.005 Å.