High power pulsed thulium doped fibre lasers and their applications

Abstract

This thesis presents the development of a high-peak-power, gain-switched diodeseeded, thulium doped fibre master oscillator power amplifier (MOPA), along with its various applications in nonlinear frequency conversion. To exploit the peak power scalability of a large-mode-area (LMA) thulium doped fibre (TDF), a three-stage MOPA structure was first demonstrated to produce 1-MHz, 52-ps pulses with a maximum average/peak output power of 3.94 W/76 kW. A fourstage configuration was proposed to enhance the overall nonlinear threshold of the system, thereby scaling the pulse peak power to a higher level. Eventually, 35-ps pulses with a record-breaking peak power of 295 kW and a maximum average output power of 10.34 W were obtained from this nearly all-fibre thulium doped fibre MOPA system. The presented high-peak-power thulium doped fibre MOPA systems were used to demonstrate stable and flexible laser sources with a combined operation window from the visible to the mid-infrared. 2-µm-pumped supercontinuum (SC) generation in fluoride fibres has demonstrated an ultra-broadband spectral output from 750 nm to 5 µm with a total output power of 1.76 W. Frequency up-conversion of the high-power thulium doped fibre MOPA was also investigated based on periodically poled-lithium-niobate (PPLN). Maximum output powers of 2.4 W and 0.69 W were achieved in second harmonic generation (SHG) and fourth harmonic generation (FHG), respectively. Besides, an optical parametric generator (OPG) and an optical parametric amplifier (OPA) based on orientation-patterned GaAs (OP-GaAs) were demonstrated to produce signal and idler pulses with wide wavelength-tuning ranges from 2550 nm to 2940 and from 5800 nm to 8300 nm, respectively

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ORCID for David Richardson: orcid.org/0000-0002-7751-1058

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