Diode-pumped two micron solid-state lasers

Rights statement
Awarding institution
  • University of Strathclyde
Date of award
  • 1997
Thesis identifier
  • T9023
Qualification Level
Qualification Name
Department, School or Faculty
  • This thesis presents an investigation of diode-pumped two micron solid-state lasers, concentrating on a comparison of the cw room temperature operation of Tm:YAP, Tm,Ho:Y AP and Tm,Ho:YLF. Dopant concentrations in YAP were 4.2% thulium and 0.28% holmium; in YLF they were 6% thulium and 0.4% holmium. Thermal modelling was carried out in order to provide an insight into the thermal lensing and population distributions in these materials. Laser operation was achieved utilising an end-pumping geometry with a simple two mirror standing wave resonator. The pump source for these experiments was a 3 W laser diode. Maximum output power was achieved with Tm:Y AP, generating 730 mW of laser output, representing 42% conversion efficiency in terms of absorbed pump power. Upper bounds on the conversion efficiency of Tm,Ho:Y AP and Tm,Ho:YLF laser crystal of 14% and 30% were obtained, with corresponding output powers of 270 and 660 mW. In all three cases, the output beam was TEMOO in nature. Visible upconversion fluorescence bands in the green and red were identified in Tm,Ho:Y AP and Tm,Ho:YLF, with additional blue emission from the latter, all assigned to transitions on holmium. The principal upconversion mechanisms in these materials all involved the holmium first excited state. Upconversion in Tm:Y AP was negligible. The spectral output of Tm:Y AP consisted of a comb of lines in the range 1.965 to 2.020 j.Ull. For both the double-doped crystals, the laser output was multilongitudinal mode on a single transition, wavelength 2.120 Ilm in YAP, 2.065 j.Ull in YLF. In the time domain the output of Tm:YAP was dominated by large amplitude spiking, unlike both of the double-doped laser crystals. The long lifetime of the thulium upper laser level (4.4 ms) provided very weak damping of the spiking. Excitation sharing between thulium and holmium, with a measured characteristic lifetime in YAP of 11.9 IlS and YLF of 14.8 1lS, provided strong damping of any spiking behaviour.
Advisor / supervisor
  • Payne, John
  • Ferguson, A. I. (Allister I.)
Resource Type