Scanning Fabry-Perot interferometer: performance and optimum use in the far infrared range

A compact scanning Fabry-Perot interferometer using metallic meshes as reflectors is described. Its performance characteristics such as finesse, transmission, and resolution are measured as functions of the interference order for several wavelengths in the 100–400-μm range. The good agreement found between theory and experiment leads to a set of curves from which the effective finesse of the instrument and its optimum use, for a fixed far infrared wavelength and given meshes, can be predicted. It is found that the effect of the incident light cone angle is more important than that of surface defects of parallelism of the meshes and that it limits the maximum resolution.