Chromium-doped Yttrium-Aluminum Garnet (Cr⁴⁺:YAG)

I. Introduction

As a novel saturable absorbing material, Tetravalent Chromium-doped Yttrium- Aluminum Garnet(Cr⁴⁺:YAG) is an excellent and convenient crystal for passively Q-switching diode-pumped or lamp-pumped Nd:YAG, Nd:YVO₄, Nd:YLF or other Nd and Yb doped lasers (wavelength from 1.0 to 1.2 mm). Due to its specific properties: broad absorption band (at the vicinity of 1 mm), high damage threshold (> 500 MW/cm²),  long lifetime, large

absorption cross section (in the near IR), good thermal stability and heat dissipation (especially at high repetition rates) and easy operation, Cr⁴⁺:YAG will replace the saturable absorbers such as Dye cells and acetate films, and color-center crystal LiF:F₂^-, which are commonly used as passive Q-switching materials, and meet the requirements of reliable, simple, compact and effective laser systems, for example, range-finders and military systems.

When used for passive Q-switching of Nd:YAG laser, a pulse width of 8.3 ns and a Q-switching efficiency of 56.9% were obtained. Cr⁴⁺:YAG was successfully used for the Q-switching of the slab laser with a big cross-section, Raman shift 1.54 mm laser with a high repetition and the LD-pumped CW Nd:YVO₄ laser for the first time.

Cr⁴⁺:YAG is also a laser crystal with tunable output wavelength from 1.35 mm to 1.6 mm. It can

generate ultrashort pulse laser (to femtosecond) when pumped   by Nd:YAG laser at 1.064 mm.

Beijing Gospel OptoTech Co. (GOT) now provides lots of Cr⁴⁺:YAG discs used as with high optical quality and the initial transmission from 1% to 99%. Diameters of Cr⁴⁺:YAG discs are from 2 mm to 25 mm, and thickness from 0.2 mm to 10 mm. We also supply Cr⁴⁺:YAG rods with 2~10 mm diameters and up to 80 mm length as tunable laser host.