Abstract
D.Phil. (Electrical Engineering)
The field of fiber lasers and fiber optic devices has experienced a sustained rapid growth. In particular, all-fiber Q-switched lasers offer inherent advantages of relatively low cost, compact design, light weight, low maintenance, and increased robustness and simplicity over other fiber laser systems. In this thesis, a design of a new Q-switching approach in all-fiber based laser is proposed. The Q-switching principle is based on dynamic spectral overlapping of two filters, namely fiber Bragg grating based filter and fiber Fabry-Perot tunable filter. When the spectra overlap, the filter system has the maximum transparency, the laser cavity has minimal losses and it can release the stored power in the form of the giant pulse. Using this Q-switching technique, experimental construction of an all-fiber active Q-switched Erbium-doped fiber lasers is successfully demonstrated in both ring cavity and linear cavity fiber laser configurations. The output peak power of 9.7 W and time duration of 500 ns are obtained at 1 kHz of repetition rate for ring cavity Q-switched Erbium-doped fiber laser; and 5.6 W output peak power with a 450 ns pulse time duration are achieved for linear cavity Q-switched Erbium-doped fiber laser at the same repetition rate. The repetition rate of the pulses can be continuously varied from a single shot to a few kHz...