High power Q-switched Tm:YALO lasers

Abstract

We have demonstrated 50 W of output power from a free-running Tm:YALO laser at 1940 nm. We have also obtained Q-switched operation with 7 mJ of output energy at a 5 kHz repetition rate. OCIS Codes: (140.3580) Lasers, solid-state; (140.3070) Infrared and far-infrared lasers.Tm:YALO lasers are useful pump laser sources for Ho:YAG lasers [1-4], 2 µm sources for laser radar applications, Cr:ZnSe lasers, which provide widely tunable output from 2.1 µm to 3 µm [5,6], and optical parametric oscillators (OPOs) [7]. Higher power and Q-switched Tm:YALO lasers are needed as better pump sources for higher power Ho:YAG and Cr:ZnSe lasers. In this paper, we report a 50 W free-running Tm:YALO laser and a 7 mJ laser Q-switched with a 5 kHz pulse repetition rate.The Tm:YALO laser cavity configuration is shown on the left of Fig. 1. The gain medium is a Tm:YALO laser rod with undoped YALO end caps that is dual end-pumped by 795 nm fiber coupled laser diodes. The laser resonator consists of a normal incidence high reflector, the 3% Tm doped YALO rod, two 45° angle-of-incidence dichroic fold mirrors, a Brewster cut TeO 2 acousto-optic modulator (AOM) for Q-switching, and an output coupler. Both the HR end mirror and the output coupler have radii of curvature of 10 cm. The laser output is polarized due to the natural birefringence of the Tm:YALO crystal. As seen in the photograph of the system on the right of Fig. 1, this is a self-contained, engineered laser system. The laser utilizes a watercooled base upon which are mounted the laser rod mount and inner enclosure (center). The pump diodes are hard mounted to a vertically oriented cooling plate. The entire assembly has dimensions of 31.5 cm W x 42 cm L x 16 cm H. Fig. 1. Schematic of the resonator (left) and photograph of the complete Tm:YALO laser (right).

Infrared (2–12 μm) solid-state laser sources: a review

“…In Q-switched pulsed regime, the reported average power also reach the 30 W level in bulk lasers with a nearly diffraction limited beam [7]. The pulse duration was typically 100 ns with a repetition rate of several kilohertz using Tm:YAlO 3 as a laser material.…”

Self-pulsing in Tm-dopedYAlO3lasers: Excited-state absorption and chaos

“…Tm:YA103 (or Tm:YAP) lasers are of particular interest due to their high efficiency [1], excellent thermomechanical properties, and natural birefringence of the crystal. A major drawback of Tm:YA103 lasers is their tendency to self-pulse, even under continuous-wave (cw) pumping [2][3][4], as shown in Fig. 1.…”

“…The origin of the self-pulsing is not well understood, al though it has been suppressed using various types of feedback, including using intracavity acousto-optic modulators [2,3] and pump diode current actuation [4], A number of mechanisms have been proposed to explain the self-pulsing in Tm:YA103 lasers, such as pump power fluctuations [5], mechanical instabilities, and saturable absorption by water in the air of the laser resonator [6]. However, these explanations do not explain the observation of self-pulsing in all cases.…”

Actively Q-switched, diode pumped thulium laser

“…Such conditions can satisfy: the lamp pumped Cr,Tm,Ho:YAG lasers, optical parametric oscillators (OPO's) pumped by high peak power Nd lasers [4,5], and developed in the last decade diode pumped lasers on Tm or Tm & Ho doped crystals [6][7][8] and hybrid lasers [9,10]. Because of quasi-three-level scheme, the conventional lamp pumped Cr,Tm,Ho:YAG lasers could operate only in pulse regime with low repetition rates not higher than few dozens of Hz.…”