BIREFRINGENCE COMPENSATION AND TEM00 MODE ENHANCEMENT IN A Nd: YAG LASER

Abstract

A Nd: YAG laser has been operated under strong thermal focusing and birefringent conditions and has yielded both linearly polarized output with negligible power loss and TEM00 output of 50–70% of the multimode power. The laser consisted of two Nd: YAG rods separated by a 90° crystal quartz polarization rotator together with a convex mirror and used no special cooling techniques. The performance of this laser, which agreed with theoretical predictions, indicates that this design approach may be generally applicable to the problem of thermally induced aberrations in such systems.

Faraday Isolators for High Average Power Lasers

“…It is well known that a 90 0 polarization rotator placed between two identical phase plates with linear eigen polarizations provides total compensation of birefringence (Scott & de Wit, 1971). If there is also circular birefringence in these plates, this statement is valid only when the directions of rotation of the polarization plane in the plates are different.…”

“…The polarization distortions which a beam acquires when passing through the first MOE, are compensated, though not totally as in laser amplifiers (Scott & de Wit, 1971), but rather partially yet efficiently when passing through the second MOE. For a super-Gaussian beam (29) one can easily show that formulas (34-38) remain valid at any m, if А 2 is replaced by А 2 (m).…”

270-W 15-kHz MOPA System Based on Side-pumped Rod-type Nd:YAG Gain Modules

“…Such rod-type solidstate gain modules, however, have intrinsic problems such as thermal lensing and thermal birefringence which lead to a degradation of beam quality and an increase of depolarization loss [5,6]. Although some schemes have been proposed for the compensation of the thermal birefringence [6][7][8], it is still challenging to efficiently compensate for the combined effects of the thermal lensing and the thermal birefringence.…”

“…Experimentally, the above condition can be satisfied when the focused point generated between two lenses is positioned exactly at the middle point between two lenses. With the proper image relay, one can compensate for thermal birefringence easily by putting a 90° quartz rotator between two rods [7].…”

High-average-power diode-pumped Yb:YAG lasers

“…One technique, which was originally demonstrated in 1970, can to a great extent eliminate birefringence and bifocussing effects by using two identically loaded rods separated by a 90° rotator 16 . Recently, there have been several reports of groups using this birefringence compensation technique to great success with diode-pumped Nd:YAG lasers 17 .…”