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Study On Coke - Based Solid - State Q - Switched And Mode - Locked 2μm Lasers

Posted on:2016-12-16Degree:DoctorType:Dissertation
Country:ChinaCandidate:C J JinFull Text:PDF
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Lasers operating in eye safe spectral region around 2μm, because of working in the atmospheric window and corresponding to the water absorption peak, have been proven very important due to their variety of application in coherent detection laser radar, laser medical, high resolution molecular spectroscopy, photo-electronic warfare. Also,2μm lasers are efficient pump sources of optical parametric oscillators (OPOs) to obtain 3~5μm laser. For above reasons, lasers around 2μm region have attract more and more research interesting. Graphene is now believed to be a promising alternative material for saturable absorption (SA) use because of its gapless linear dispersion of Dirac electrons, deep modulation depth, ultrafast carrier relaxation time, low optical absorption coefficient and wide operation range (visiable light-Thz), especially in 2μm lasers. In this dissertation, we has systematic research graphene Q-switching and mode locking theory and laser operation in different pump methods and laser materials based 2μm laser systems. Based on graphene and volume Bragg grating (VBG), we designed simple and robust single single-frequency passively Q-switched Tm:YAP laser and wideband tunable passively Q-switched Tm:YAP laser. The main research content is summarized below:(1) Research of graphene-based passively Q-switched Cr:Tm:Ho:YAG laser.We theoretical analyzed different parameters of pump method, focus cavity, resonator structure, cooling system and laser material for Cr:Tm:Ho:YAG laser system and compared them influencing in laser output through experiment. Finally, we obtained graphene-based passively Q-switched Cr:Tm:Ho:YAG laser operation and analyzed laser output beam properties. Over 5 W Q-switched laser output was achieved. We established rate equations of graphene Q-switched Cr:Tm:Ho:YAG laser system to explain satellite pulse phenomenon which was discovered in experiment.(2) Research of graphene-based passively Q-switched Ho:YAG laser in-band pumped by a diode-pumped Tm:YLF solid-state laser.Based on research of crystal luminescence mechanism and rate equations, we studied the laser output beam properties of graphene-based passively Q-switched Ho:YAG laser in-band pumped by a diode-pumped Tm:YLF solid-state laser. We discussed the influence of two crystals heating effect on laser pulse. Using of self-fabricated easy, low loss, high quality and stability graphene SA, passively Q-switched Ho:YAG laser was finally obtained. To the best of our knowledge, a Q-switched pulse duration as short as 632 ns was obtained with the repetition rate of 43 kHz, the average output power of 572 mW and the single pulse energy of 13.3μJ at the wavelength of 2096.5 nm.(3) Research of graphene-based mode-locked Tm:YLF laser.We studied the modulation depth, saturation flux and mode-lock established time of graphene and analyzed the influence of these important properties on ultrafast laser. Then we theoretically analyzed the dispersion compensation of laser chrip in mode-locked Tm:YLF laser. Graphene-based mode-locked Tm:YLF laser was finally obtained based on GaF2 prism dispersion compensation. The laser generated a low noise of 473 fs pulses at 70.2 MHz, with 146.5 mW average output power, demonstrating the passively CW mode-locked operation based on the output-coupling GSAM in the 1.9μm mid-IR.(4) Research of wideband tunable single-frequency graphene-based passively Q-switched Tm:YAP laser.Through study of Kogelnik coupled wave theory, we established numerical simulation of reflecting VBG and analyzed the influence of coupling constant, interaction length, incident angle and wavelength on diffraction efficiency. Based on the theory research, compact and stable V-shaped single-frequency Q-switched Tm:YAP laser was obtained. We achieved stable single-frequency Q-switched laser with line width of about 4.2 MHz at central wavelength of 1988.8 nm. The average output power of the single-frequency pulse laser was measured as 724 mW, corresponding to the single-pulse energy of 7.5μJ with the repetition rate of 96.2 kHz.We proposed wideband tunable Z-shaped Q-switched Tm:YAP laser design based on VBG and graphene, and then realized stable laser wavelength tunable operation. After that, we studied the laser output properties of windeband tunable graphene-based passively Q-switched Tm:YAP laser in details. The laser wavelength was continuously tunable from 1965.2 to 2000.7 run (range of 35.5 nm). A maximum output power of 920 mW was obtained at a wavelength of 1989.3 nm, corresponding to the pulse duration of 2.1 μs, the repetition rate of 91.6 kHz, and the single pulse energy of 10.1μJ.
Keywords/Search Tags:graphene SA, Q-switched laser, Mode-locked laser, volume Bragg grating, single-frequency laser
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