A Fourier transform spectrometer based on a modified Sagnac interferometer is described. The instrument uses one or more gratings as dispersive elements to greatly improve the spectral resolution, and in-line optics to match the beam size in the interferometer to optimize the efficiency. The resolution can approach about 0.6 GHz at about 632.8 nm (.lamda./.DELTA..lamda.=8.4.times.105). A CCD or photodiode array is used as the detector and the fast Fourier transform of the fringe pattern is performed by a computer. Some embodiments employ no mechanically moving parts; therefore, they are compact and easy to align. Practical applications include remote sensing, process monitoring, and basic research. The fast response time of the detector also allows real time spectral analysis.
REFERENCE TO RELATED APPLICATIONS
The present application claims a priority benefit of U.S. Provisional Patent Application Ser. No. 60/577,512, filed on Jun. 4, 2004, titled "Double-grating sagnac fourier transform spectrometer," which is hereby incorporated by reference herein in its entirety.
