Abstract

Repetitive Q-switched miniature laser sources around 1 5μm are useful tools for applications such as time-of-flight rangefinding. Until now, the only laser transition available in this wavelength region was the optical transition ⁴I_13/2 →⁴I_15/2 of erbium ions in phosphate glasses. However, it was pointed out recently that a continuous wave laser emission at 1 5μm based on the ³H₄→³F₄ optical transition of thulium ions can be obtained easily in fluoride crystals such as LiYF₄ thanks to sensitization with Yb³⁺ ions. The advantage of such codoping is that Yb³⁺ ions act both as a sensitizer to absorb the emission from high power InGaAs laser diode and, at the same time, depopulate efficiently the lower ³F₄ level and recycle the energy up into the ³H₄ emitting level Moreover, unlike the Er-glass system, Yb:Tm:YLF presents good thermomechanical properties allowing higher pulse repetition rates and average output powers

© 2000 IEEE