Thulium doped fibre lasers in continuous-wave and pulsed regimes

[摘要] ENGLISH ABSTRACT: The following work focuses on the development and characterization of efficient,high-power, Thulium doped fibre lasers. Lasers emitting light around ~2 μm havegenerated a large amount of interest owing to the range of applications requiring andutilizing light centred on this wavelength. Laser light in this emission band isconsidered 'eye-safe which makes it ideal for applications where eye-safety isparamount. The aim of this work is to develop expertise in Thulium doped fibrelasers. Background information relevant to the functioning of Thulium doped fibrelasers is presented. An existing diode pumped, CW Thulium doped fibre laser ischaracterized. The wavelength output as well as the efficiency of the fibre laser wascharacterized for different fibre temperatures, indicating shorter wavelength output forlower fibre temperatures. Additionally, initial results indicate that without anywavelength control (fibre Bragg gratings, volume Bragg grating), the spectrum andlaser output is temporally unstable. The design, development and characterization of adiode pumped, CW and Q-switched Thulium doped fibre laser is discussed. Thedesign process and considerations are discussed in detail. Different feedbackelements, including a volume Bragg Grating, are utilized to constitute the laserresonator as well as two lengths of doped fibre. The CW fibre laser is characterizedwith regard to its slope efficiency, spectral output, temporal behaviour, beam profileand polarization. A maximum slope efficiency of 37 % was obtained for 6.5 metres ofactive fibre, only limited by the onset of thermal damage of the fibre ends. Pulsedmode of the fibre laser was facilitated with the aid of an Acousto Optic Modulator(AOM). At a pulse repetition rate of 10 kHz and average power of 2 W, a maximumpulse energy of 200 μJ is obtained with pulse durations of 77 ns. This corresponds toa maximum peak power of 2.6 kW

[发布机构] Stellenbosch University