Performance evaluation of ∼2.1 μm microchip laser operation in Ho3+ doped germanate glass

Abstract

An in-band pumped continuous wave (CW) ∼2.1 μm microchip laser is presented for the first time based on a short cavity Ho³⁺ doped germanate glass (GeO₂-PbO-Ga₂O₃–Na₂O: GPGN). A 1.94 μm, 5 W Tm³⁺ fiber laser was employed for the excitation of the Ho³⁺ ions. A 19% laser slope efficiency was achieved in a simple, unoptimized plane parallel Fabry-Perot cavity configuration. A positive thermal lens was estimated in the laser cavity with a sensitivity factor of S ∼31 m⁻¹W⁻¹ and an optical path distortion value exceeding 6 μm. The laser results along with the analysis of the thermal lens indicate that with improved thermal management and an optimized cavity configuration GPGN is a promising gain medium for microchip laser operation around 2.1 μm.