Tunable Cr:Nd:GSGG Lasers Pumped by Red Diodes

Abstract

Laser operation of Nd+3-doped gadolinium scandium gallium garnet (Nd:GSGG) has been first shown by Kaminskii et al. in 1976 [1]. In earlier studies, flaslamp or solar pumping of Nd:GSGG has been explored, and narrow absorption bands of the Nd+3 ion, that overlaps poorly with these broadband emitters resulted in low laser efficiencies. As a solution, co-doping with chromium ion (Cr:Nd:GSGG) has been applied to generate additional broad absorption bands in the visible to improve the absorption as well as the laser efficiency [2-3]. With the development of semiconductor technology, laser diode pumping has become the dominant excitation scheme for Nd-based laser systems [4-6]. Usually, laser diodes at the sharp absorption peaks of Nd:GSSG around 808 nm or 883 nm have been employed [4-5]. As an alternative, Cr co-doped samples provide broad absorption bands around 645 nm, in a spectral region where low cost laser diodes also exist [6]. While using these broad absorption bands, thermal control of the diode junction temperature, narrowband diode operation, and careful selection of diode central wavelength is not required. However, the quantum defect is higher, lowering the laser efficiencies.