Diode laser pumped solid state lasers
This thesis deals with the development of diode laser pumped solid state lasers. The earliest work presented enabled 125W peak power, single frequency Q-switched pulses to be obtained from a 100mW diode laser pumped Nd:YAG laser. Using a 500mW diode laser as a pump source for C.W. Nd:YAG and Nd:YLF oscillators an Yb:Er fibre laser was pumped, producing 0.75mW C.W. power at a wavelength of 1.56µm. Acousto-optic mode-locking techniques were used to provide C.W. mode-locked pulse durations in Nd:YAG and Nd:YLF of 55ps and 18ps respectively, at repetition rates of 240MHz. Frequency modulation mode-locking was shown to be a superior technique, giving pulse durations of 11.5ps and 10ps in diode laser pumped Nd:YAG and Nd:YLF oscillators respectively. FM operation of diode laser pumped Nd:YAG lasers was investigated, yielding a maximum FM bandwidth of 70GHz. Spatial hole burning was considered to be an important factor in this result. Using a 1W diode laser to pump a mode-locked and Q-switched Nd:YLF oscillator peak power levels of 70kW were obtained at a wavelength of 1.047µm. Frequency doubling this output in MgO:LiNbO3 with an energy conversion efficiency of 47% enabled other tunable lasers to be pumped using the second harmonic. Firstly, a synchronously pumped rhodamine 6G dye laser is described which is capable of producing 3.2ps mode-locked pulses in a Q-switched envelope with peak powers of around 10kW. Secondly, a synchronously pumped doubly resonant optical parametric oscillator tunable between 983nm and 1119nm is described. Lastly, a Ti:Sapphire laser producing 400ns pulses with peak powers of 3W at a wavelength of 755nm is demonstrated. This oscillator could be wavelength tuned between 746nm and 838nm. A highly efficient method of frequency doubling C.W. mode-locked lasers was developed. Using an external resonant cavity a frequency doubling energy conversion efficiency of 61% to 532nm was achieved, giving 87mW average power in 8.5ps pulses.