Tunable mid-infrared filter based on Fabry-Perot interferometer with two movable reflectors

A tunable IR filter based on a Fabry-Perot interferometer with two movable reflectors is reported. The infrared filter can be tuned over a wavelength range from 8 m to 11 m with voltages lower than 63 V. The FWHM bandwidth is lower than 200 nm and the peak transmittance is larger than 70 %. Simulation and practical shock test, both showed that the device can withstand 1500 g, 0.5 ms shocks according to Mil-Std-883G, method 2002.4, test condition B. The new infrared filter measures 8.5 mm x 8.5 mm and is suitable for the integration in a TO-8 housing in combination with a broadband infrared detector. The design benefits from relatively low stiffness of the mirror suspensions, compensation of vibration and gravitation induced forces possibly influencing the central wavelength and much lower actuation voltages as a result. Both reflector carriers are movable and are actuated by electrostatic forces.