A optomechanical design for Fabry-Perot Interferometer

Fabry-Perot Interferometer are particularly useful for high-resolution spectroscopy and other applications including astronomy and intra-cavity laser-line narrowing. Fabry-Perot etalon with diameters 1 mm square to 100 mm circular are commercially available and using a conglomerate of optomechanical components and lenses form a Fabry-Perot Interferometer (FPI) system. The etalon when illuminated with a known wavelength laser beam through fore-optics transmits the interference pattern onto a detector through back-optics and thus the image formed on the detector is a concentric circular interference fringe pattern. A sharp pattern with a maximum number of fringes is achieved by introducing a correct combination of the fore and back optomechanical system. Commercially available interferometer inclusive of the optics and the etalon are expensive and beyond the purchasing capacity of budget-conscious users. An alternative to these ready-made interferometer is to manufacture an indigenous optomechanical system and integrate it with the commercially available etalon that delivers a low cost, less weight, and a fairly simple FPI. This report discusses in detail one such system designed and developed in our institute laboratory. The important parameter finesse is calculated and its accuracy is found to be 85%. The developed system with further modifications, like the insertion of the field-of-view module, may serve as an alternative for the large size-based integrating sphere systems that are deployed in the field for observations.