Distributed feedback dye-doped sol-gel silica lasers

Solid state dye lasers with narrow linewidth and short pulse duration have attracted increasing attention because of their potential applications. Distributed feedback (DFB) laser is an effective compact coherent light source capable of tunable output with narrow linewidth. In this dissertation, lasing characteristics of dye doped sol-gel silica distributed feedback lasers have been investigated. The optical properties of sol-gel silica deduced from measurements of DFB laser output have also been studied.; High optical homogeneity sol-gel silica slabs doped with desired concentration of Rhodamine 6G (MG), Coumarin 460 (C460), or Exalite 377E (E377) dye have been fabricated. Spatial periodic gain modulation in the dye doped sol-gel silica slab was created by crossing the diffracted pump beams from a holographic grating (1800 lines/mm) used as a beam splitter. Tunable laser emission in the yellow, the blue, and in the near ultraviolet region has been generated from the distributed feedback geometry using sol-gel silica slabs doped with R6G, C460 or E377 dye respectively. Wavelength tuning range of approximately 20 nm around the emission centers (562 nm, 480 nm, 376 nm) has been realized by varying the pump beams intersection angle. The laser linewidth was of the order of 60∼80 pm when pump energy was several times over the threshold. Laser pulse trains with sub-nanosecond spikes were induced. A slope efficiency of approximately 4.5% has been obtained.; The time behavior of distributed feedback R6G doped sol-gel silica laser has been studied using a N₂ laser as the pump source. Sub-nanosecond pulse duration has been obtained. The pulse number in the output pulse train is sensitive to the pump energy. Experimental results of the time behavior are in good agreement with theoretical calculations.; The lasing performance of tunable distributed feedback dye-doped sol-gel silica laser operating at different Bragg scattering order (M = 1, 2, 3) has also been studied. Distributed feedback laser operating at higher Bragg scattering order was observed at higher pump energy threshold and with lower energy conversion efficiency. The energy conversion efficiency of 0.7% (for M = 3) and 11% (for M = 2) has been achieved.; Based on the Bragg scattering condition and the temperature dependence of the refractive index (η) of the gain medium, temperature tuning of the laser output was realized in experiment from the distributed feedback R6G doped sol-gel silica/PMMA lasers. Wavelength tuning from 573 nm to 556 mm has been demonstrated by varying the temperature from 21°C to 58°C. The laser linewidth was kept below 0.5 mm within the whole tuning range. The thermal coefficient of the emission wavelength has been measured. Finally the thermal coefficient of refractive index of sol-gel silica has been derived from these experimental data. Discontinuity in dη/dT curve attributable to phase transition has been observed in dye doped sol-gel silica slab and PMMA bulk. Temperature tuning performance of DFB laser using high temperature treated sol-gel silica as the gain medium has also been investigated.