Mode referencing of an external cavity diode laser for continuous frequency stabilization

Abstract

The output of an external cavity diode laser (ECDL) is frequency stabilized to a water (H2O) vapor absorption line at 935 nm using wavelength modulation spectroscopy (WMS) by means of a dual-feedback locking loop. A novel mode-referencing technique is presented that, in conjunction with the feedback locking mechanism, helps improve the overall frequency-locking system. The mode-referencing enables the device output to maintain its locked frequency in the presence of environmental and other effects, which may cause the operational characteristics of the laser to drift.