Single-frequency emission at 532 nm from a unidirectional, internally doubled, diode laser array pumped, Nd:YAG ring laser

Abstract

Single-frequency operation of an internally doubled Nd:YAG laser is one method of eliminating the high frequency amplitude fluctuations that are often observed in the output of such a device when multilon-gitudinal-mode oscillation occurs. A single-frequency output is also desirable for many holographic and spectroscopic applications. Single-longitudinal-mode operation of a Nd:YAG laser can be accomplished through the elimination of spatial hole burning in the gain medium or through the insertion of a spectrally selective loss element in the laser cavity.1 The first method is preferable in an internally doubled device since it adds less intracavity loss and maximizes the harmonic conversion efficiency. The traveling wave intracavity field in a unidirectional ring laser has been shown to effectively eliminate spatial hole burning in Nd:YAG.2 By inserting a crystal of KTP in the cavity of a unidirectional, laser diode array pumped Nd:YAG ring laser operating at 1064 nm, we have been successful in producing 0.75 mW of single frequency output at 532 nm. The overall conversion efficiency of pump radiation to harmonic output is 0.2-0.3%. It is anticipated that overall pump conversion efficiencies of a few percent are possible with optimization of the cavity design and the use of lower loss optics.