Knowledge Bank

We have built an automatic infrared $wavemeter1$ based on a fringe-counting Michelson interferometer. It features compact vacuum-tight construction, a vernier technique to ensure integral fringe counts, and the use of an inexpensive home computer (Radio Shack Co-Co 2) board to implement direct automatic read-out of laser wavenumber ($cm-1$) or wavelength ($/mum$). The design emphasizes compactness and ease of use, and its accuracy is generally limited by diode laser wavefront curvature and alignment effects. For operation in the 5 to $10\mu m$ region, the accuracy is usually about $0.003cm-1$ or better, and this can be improved to about $0.001cm-1$ by a single calibration in a given region to correct for alignment effects. We will discuss some test results obtained with OCS, as well as the problems and advantages encountered in the routine use of this instrument.