Double coherent solid-spaced filters for very narrow-bandpass filtering applications

Abstract

We report in this paper the study of a double coherent solid-spaced Fabry–Perot filter. The utilization of thick spacers enables to take advantage of their high optical quality and to use simple broad-band dielectric mirrors. Such single cavity filters are easy to manufacture and exhibit very low absorption and scattering levels. In a preliminary demonstration phase, the adjustement of the air gap thickness insuring the coherent coupling of both filters is done with a piezoelectric actuator. Experimental results concerning a double coherent solid-spaced filter centered at 1.56 μm with a maximum transmission of 98% and a full-width at half-maximum of 0.5 nm are given. The possible improvements of such components are discussed.