Classification of single-mode laser emission based on interferograms measured using a Fizeau wavemeter.

Optical interferometry using high Q-factor etalons requires interrogation light sources that operate in a single longitudinal mode to achieve high detection sensitivity. To characterize and monitor the output of the source, external instruments, such as spectrometers and optical spectrum analyzers, are often used. In this work, interferograms measured using a commercial wavemeter were evaluated using a set of heuristic metrics to classify the output of two lasers as single-mode or multi-mode. The wavemeter is based on Fizeau interferometers and is typically used for high-precision wavelength measurements. The method was validated on interferograms produced by the output of a visible and near-infrared external cavity diode lasers, and was found to allow the classification of single- and multi-mode emissions with high specificity. The results were compared with measurements made using an optical spectrum analyzer, a spectrometer, and, for the visible laser, a scanning Fabry-Perot interferometer. To provide an example of a practical application, the classification method was applied to the measurement of acoustic transients using an interferometric ultrasound sensor. The wavemeter-based method may be useful in applications where a combination of high spectral resolution, fast data acquisition, and the ability to classify single-mode emissions are advantageous.