Laser resonators rely on small differences in the reflectivity of fold mirrors for different polarization states to give a stable linearly polarized output. In some cases, the small reflection gaps of the total reflector mirror coatings are not enough to keep the polarization from fluctuating. Using specific properties of the materials selected in optical coating design, we are able to increase the differences in the reflection of S-polarization compared to P-polarization and achieve a truly stable “locked” polarization.

The PLM-HR mirror coating provides optimized S-Pol reflection (>99.90% for S-Pol), with low enough P-Pol reflection (<93% P-Pol) to enable effective phase locking while still reflecting maximum reflection at the desired S Polarization. It is internal cavity radiation resistant, suitable for both Cu and Si mirrors and can be used in a variety of different resonator type.

Coating	Substrate	%S-Pol@45°@10.6	%P-Pol@45°@10.6	%R@45°@0.6328
PLM	Si	99.5%	≤90%	-
PLM-W	Cu	99.8%	≤90%	-
PLM-HR	Cu	>99.9%	≤97%	≥65%@630-670nm
PLM-HR	Si	>99.9%	≤93%	≥65%@630-670nm