Diode-pumped Tm³⁺-doped sesquioxide lasers for ultrashort pulse applications in the 2μm region

Abstract

This thesis presents the development of Tm³⁺-doped sesquioxide laser sources in the 2–2.1 μm spectral region. The primary focus of this development has been aimed towards high power diode-pumped mode-locked laser sources capable of femtosecond pulse generation. In addition to this, the early development of a compact and low threshold ultrafast laser inscribed waveguide laser has also been realised.

Continuous wave characterisation of bulk solid-state crystalline Tm:LuScO₃ and ceramic Tm:Lu₂O₃ lasers has been completed using ~795 nm multimode single emitter laser diode pump sources. Average output powers of 660 mW and 901 mW, and emission wavelengths of 2.1 μm and 2.06 μm were achieved from the Tm:LuScO₃ and Tm:Lu₂O₃ lasers, respectively. In addition, both lasers demonstrated smooth and continuous tuning ranges spanning more than 160 nm in the ~2–2.1 μm spectral region.

In the mode-locked regime, pulse durations as short as 170 fs were recorded at an average output power of 113 mW and an emission wavelength of 2094 nm from a diode-pumped mode-locked Tm:LuScO₃ laser through the use of an ion-implanted InGaAsSb quantum-well-based semiconductor saturable absorber mirror. A diode-pumped Tm:Lu₂O₃ laser, utilising the same semiconductor saturable absorber mirror, was able to generate pulses as short as 278 fs at an average output power of 555 mW and a wavelength of 2081 nm through the use of a steeply diving optic axis birefringent filter. This same filter was also used to demonstrate broadly tunable femtosecond pulses in both laser configurations. Subsequent amplification of the ultrashort pulse laser sources realised maximum amplified average output powers of 540 mW and 855 mW, respectively.

The results presented in this thesis demonstrate the potential for diode-pumped Tm³⁺-doped sesquioxide laser sources to be developed into an enabler technology for the advancement of a number of photonics applications and techniques in the mid-infrared region.