Abstract
The concept of Yb-doped double tungstate microchip lasers is verified and scaled to the multi-watt power level. The active element is a 2.6 mm-thick Yb:KLuW crystal cut along the Ng optical indicatrix axis. Maximum continuous-wave output power of 4.4 W is extracted at 1049 nm with a slope efficiency of 65% and an optical-to-optical efficiency of 44% with respect to the absorbed pump power. The laser emission is linearly polarized and the intensity profile is characterized by a near-circular TEM00 mode with M2x,y < 1.1. Due to low intracavity losses of the microchip laser, laser operation at wavelengths as long as 1063 nm is achieved. The mechanism of the thermal mode stabilization in the microchip cavity is confirmed. At very low resonator losses polarization-switching between E || Nm and Np oscillating states is observed and explained on the basis of spectroscopic and thermal lens characteristics.
Highlights
The microchip laser concept opens up new opportunities for diode-pumped solid-state lasers
We demonstrate an efficient multi-watt Yb:KLuW microchip laser based on “bulk” crystal geometry
A maximum output power of 4.4 W is obtained for TOC = 10% connected to the maximum slope efficiency of 65%, calculated with respect to the overall absorbed diode power
Summary
The microchip laser concept opens up new opportunities for diode-pumped solid-state lasers It implies a laser crystal with two flat mirrors attached or directly coated on its endfaces, resulting in a compact setup insensitive to misalignment and a low loss cavity [1]. Yb:DTs possess intense and wide absorption and emission bands with strong polarization anisotropy (due to low-symmetry structure) [6] They permit high doping levels, up to 100 at.%, without significant distortion of the lattice and luminescence quenching (the latter is mainly related to the large RE3+–RE3+ separation) [7]. The crystal was cut along the Ng-axis of the optical indicatrix, resulting in a positive lens, this complex design did not allow one to further increase the output power and reach the high slope efficiencies inherent for Yb:DT lasers. We demonstrate an efficient multi-watt Yb:KLuW microchip laser based on “bulk” crystal geometry
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