Dual-purpose, compact spectrometer and fiber-coupled laser wavemeter based on a wollaston prism

A fiber-coupled, compact laser wavemeter based on a modified Wollaston prism has been constructed and evaluated. The path difference between orthogonal polarization states of the input light varies smoothly across the aperture of the prism forming an interferogram in the spatial domain that is recorded with a CCD detector array. A Fourier transform of this interferogram gives the spectral distribution of the incident light. Alternatively, for a narrow-linewidth source a fringe period measurement technique is used to obtain precision measurement of the center wavelength. Using 752 interferogram data points we obtain a wavelength precision of 1 part in 10(6). The elimination of moving parts from the design makes the recorded interferogram inherently stable.