TINY MID- AND LONG-WAVE INFRARED SPECTROMETER MODULE WITH A MEMS DUAL-BAND FABRY-PEROT FILTER

摘要

This paper reports on new dual-band Fabry-Perot-Filters (DB-FPF) and spectrometer modules, which can be operated simultaneously in the mid- and long-wave infrared by using the first and second interference order. With this design the restrictions of the usable tuning range of FP-filters, which are due to the limited free spectral range (FSR) and the bandwidth of the bragg reflectors, can be partly solved. In the LWIR Ge, ZnS and a new low refractive dielectric material were used for the reflectors, giving additional degrees of freedom for the design. In addition the tensile and compressive stress of the optical thin films was compensated within the dielectric layer stack by a sophisticated design. First samples of dual-band reflectors, optimized for 4 - 5μm and 8 - 10.5μm, were fabricated and tested in tunable FP-Filters. The reflectors exhibit a very low curvature and tilting, which gives rise to a high finesse and transmission of the filters. The DB spectrometer module is based on a dual channel pyroelectric detector. The first and second order is separated by means of a dichroic beamsplitter and two broad bandpass filters. Compared to conventional 50:50 beamsplitters this solution minimizes signal losses. The complete spectrometer module fits in a TO-8 package.