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A Ho:YAG ceramic microchip laser pumped by a Tm fiber laser at 1910 nm is passively Q-switched by single- and multi-layer graphene, single-walled carbon nanotubes (SWCNTs), and Crsup2+/sup:ZnSe saturable absorbers (SAs). Employing SWCNTs, this laser generated an average power of 810 mW at 2090 nm with a slope efficiency of 68% and continuous wave to Q-switching conversion efficiency of 70%. The shortest pulse duration was 85 ns at a repetition rate of 165 kHz, and the pulse energy reached 4.9 μJ. The laser performance and pulse stability were superior compared to graphene SAs even for a different number of graphene layers (n=1 to 4). A model for the description of the Ho:YAG laser Q-switched by carbon nanostructures is presented. This modeling allowed us to estimate the saturation intensity for multi-layered graphene and SWCNT SAs to be 1.2±0.2 and 7±1 MW/cmsup2/sup, respectively. When using Crsup2+/sup:ZnSe, the Ho:YAG microchip laser generated 11 ns/25 μJ pulses at a repetition rate of 14.8 kHz.

Trigonal langasite-type ordered silicate crystal Yb:Ca3NbGa3Si2O14 (Yb:CNGS) is a promising material for efficient ∼1 μm lasers. We report on the first passively Q-switched Yb:CNGS laser using Cr4+:YAG and V3+:YAG saturable absorbers (SAs) with a 976 nm volume-Bragg-grating-stabilized diode as a pump source. The laser crystal was a c cut 3 at.% Yb:CNGS grown by the Czochralski method. It was placed in a compact microchip-type laser cavity. With a Cr4+:YAG SA, very stable 62.2 μJ/4.4 ns pulses were achieved at a repetition rate of 22.5 kHz. The average output power was 1.40 W at 1015.3 nm, corresponding to a Q switching conversion efficiency of 90%. With the V3+:YAG SA, the pulse characteristics were 13.3 μJ/11.1 ns at a higher repetition rate of 68.4 kHz. The performance of the Yb:CNGS/Cr4+:YAG was numerically modeled showing a good agreement with the experiment.

A single-layer graphene saturable absorber is employed for passive Q-switching of an Er, Yb:GdAl3(BO3)4 (Er,Yb:GdAB) compact laser, representing the first Er-doped oxoborate laser Q-switched by graphene. This laser is based on a c-cut 1.8 at. % Er3+, 15 at. % Yb3+:GdAB crystal diode-pumped at 0.976 μm. It generates a maximum average output power of 360 mW at 1.55 μm with a slope efficiency of 23% (with respect to the incident power). Stable ∼1 μJ/130 ns pulses are achieved at a repetition rate of 400 kHz. This result represents, to the best of our knowledge, the shortest pulse duration ever achieved in bulk Er lasers Q-switched by 2D materials. Graphene is a promising material for generating nanosecond pulses at high repetition rates (MHz range) in Er-doped oxoborate lasers emitting in the eye-safe range at 1.5–1.7 μm.