Lamellar grating interferometer based compact FT spectrometers

Lamellar grating interferometers (LGI) offer compact spectrometer architecture with high spectral resolution and large clear aperture. This study investigates the diffraction based inherent limitations of LGI spectrometers in contrary to conventional Michelson type spectrometer architecture. Simulations and experiments were conducted to demonstrate and explain periodic nature of the interferogram envelope due to Talbot image formation. Simulations reveal that grating period should be chosen large enough to avoid Talbot phase reversal at the expense of mixing diffraction orders. Overall optimization effort on the LGI system reveals that it is possible to build compact spectrometers to be used directly in the field without any performance degradation in contrary to bulky FTIR systems.