MODE-HOP SUPPRESSION OF LITTROW GRATING-TUNED LASERS

Mode-hop suppression in a tunable laser employing a Littrow grating can be obtained through a simultaneous sweep of the Littrow grating angle and cavity length. The simplest way to obtain such coupled movements is to rotate the Littrow grating about a particular axis: We show theoretically and experimentally that it is necessary to improve the formalism used in previous calculations to treat the problem correctly. The current model explains the different choices made in previous studies and gives the optimal rotation point and mechanical tolerances to obtain a maximal continuous tuning range. It has been successfully tested experimentally.