Judd--Oflet analysis of spectrum and laser performance of Ho:YAP crystal end-pumped by 1.91-μm Tm:YLF laser

The Ho:YAP crystal is grown by the Czochralski technique. The room-temperature polarized absorption spectra of Ho:YAP crystal was measured on a c-cut sample with 1 at% holmium. According to the obtained Judd--Ofelt intensity parameters \varOmega₂=1.42× 10²⁰ cm², \varOmega₄=2.92× 10²⁰ cm², and \varOmega₆=1.71× 10²⁰ cm², this paper calculated the fluorescence lifetime to be 6 ms for ⁵I₇→⁵I₈ transition, and the integrated emission cross section to be 2.24× 10^-18 cm². It investigates the room-temperature Ho:YAP laser end-pumped by a 1.91-μm Tm:YLF laser. The maximum output power was 4.1 W when the incident 1.91-μm pump power was 14.4 W. The slope efficiency is 40.8%, corresponding to an optical-to-optical conversion efficiency of 28.4%. The Ho:YAP output wavelength was centred at 2118 nm with full width at half maximum of about 0.8 nm.