An investigation into optical amplifiers and upconversion lasers using rare earth doped fluorozirconate glass fibre
This thesis presents the results of a three year study into the use of trivalent rare-earth doped fluorozirconate fibre for potential diode-pumped amplifiers and upconversion lasers. A diode-pumped, high-gain, thulium-doped, fluoride-fibre optical amplifier around 0.8µm, for use in the first optical communications window, is reported. Using only one 100mW single stripe diode laser as the pump source for this first window optical amplifier, small-signal gains in excess of 20dB are reported for input signals of -10 dBm tunable from 801nm to 810nm. The noise figure for this amplifier was around 5 to 6dB, limited by back-reflected amplified spontaneous emission caused by the detection technique. Without this the noise figure would be below 4dB. The amplification of Q-switched AlGaAs diode lasers to high power using a similar thulium-doped fibre amplifier is also described. Peak powers of 12.5W useable output were observed. The pulses were 15ps long and amplified at a repetition rate of 7MHz using one 100mW single-stripe diode laser as the pump source. Thulium and praseodymium doped fluorozirconate fibres have also been investigated as possible infrared-pumped, visible upconversion lasers. Blue lasing using a praseodymium doped fibre has been optimised, while various spectroscopic measurements have been made of possible thulium upconversion systems.