A device and a method for measuring a thermal load caused by energy transfer upconversion in a laser gain crystal. Increasing the pump power multiple times so that the power meter obtains multiple thresholds for a single-frequency laser; obtaining an average pump threshold of the output laser; obtaining cavity parameters of the single-frequency laser; obtaining thermal focal lengths on the tangential and sagittal planes of the laser gain crystal inside the single-frequency laser; obtaining individual ABCD matrices of the laser system on the tangential and the sagittal planes; obtaining a thermal load at the threshold based on the ABCD transfer matrix of the laser gain crystal on the tangential plane, the ABCD transfer matrix of the laser gain crystal on the sagittal plane, and the average pump threshold of the laser system; obtaining a thermal load caused by ETU at threshold based on the thermal load at the threshold.

A laser using a laser diode and a narrow wavelength from a resonant atomic transition of a predetermined material. The gain range of the laser diode encompasses the wavelength of the resonant atomic transition. A vapor cell containing a material, such as a metal vapor, providing the resonant atomic transition forming the predetermined wavelength is placed between permanent magnets. In one embodiment the vapor cell has opposing windows positioned at a Brewster's angle and rotated 90 relative to each other. The laser produces a very narrow bandwidth of a predetermined wavelength with high power. The laser configuration eliminates several optical components reducing cost.

An optically pumped on-chip solid-state laser includes a solid gain media substrate and a laser generating structure disposed above the solid gain media substrate. The laser generating structure includes a resonator, a pump light input structure, and a laser light output structure; and the resonator is disposed between the pump light input structure and the laser light output structure, and is propped against or is in clearance fit with the solid gain media substrate.

In a resonator arrangement (1) including a resonator (2), an interferometer (9) is arranged inside the resonator (2) and includes at least a first and a second interferometer leg (9a, 9b). The two interferometer legs (9a, 9b) have optical path lengths (L1, L2) that differ from each other. According to the invention a splitting ratio is variably adjustable, with which the interferometer (9) splits radiation (8) circulating in the resonator (2) into the first and second interferometer legs (9a, 9b).