Growth, spectroscopy and SESAM mode-locking of a "mixed" Yb:Ca(Gd,Y)AlO4 disordered crystal

Abstract

We present the growth, spectroscopy, continuous-wave (CW) and passively mode-locked (ML) operation of a novel "mixed" tetragonal calcium rare-earth aluminate crystal, Yb³⁺:Ca(Gd,Y)AlO₄. The absorption, stimulated-emission, and gain cross-sections are derived for π and σ polarizations. The laser performance of a c-cut Yb:Ca(Gd,Y)AlO₄ crystal is studied using a spatially single-mode, 976-nm fiber-coupled laser diode as a pump source. A maximum output power of 347 mW is obtained in the CW regime with a slope efficiency of 48.9%. The emission wavelength is continuously tunable across 90 nm (1010 - 1100 nm) using a quartz-based Lyot filter. With a commercial SEmiconductor Saturable Absorber Mirror to initiate and maintain ML operation, soliton pulses as short as 35 fs are generated at 1059.8 nm with an average output power of 51 mW at ∼65.95 MHz. The average output power can be scaled to 105 mW for slightly longer pulses of 42 fs at 1063.5 nm.