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Study On All-Solid-State Doubly Q-Switched And Mode-Locked Laser Characteristics And Laser Stability

Posted on:2013-01-01Degree:DoctorType:Dissertation
Country:ChinaCandidate:G ZhangFull Text:PDF
GTID:1118330374480668Subject:Optical Engineering
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Laser-diode pumped solid-state Q-switched and mode-locked (QML) lasers have become a focus in the fields of lasers due to their merits such as simple structure, high conversion efficiency, high pulse stability, and high beam quality. These kinds of lasers have been widely used in many important fields such as laser ranging, micromachining, optical networks, optical communication and medicine.In this dissertation, by using a commercial fiber-coupled laser-diode array as the pump source, Nd:LuVO4, Nd:GdVO4, and Nd:Lu0.15Y0.85VO4as laser media, we have investigated the output performances of the diode-pumped dual-loss-modulated QML lasers at1064nm and1342nm with AO-GaAs, AO-Cr4+:YAG, as well as AO-V3+:YAG, respectively; the relative dual-loss-modulated QML green lasers have been realized. In addition, using EO modulator as active Q-switch, we have studied the performances of the diode-pumped dual-loss-modulated QML lasers with EO-GaAs and EO-SESAM, respectively. By inserting single-walled carbon nanotube saturable absorber (SWCNT-SA) into actively QML laser cavity, the characters of EO/SWCNT-SA and AO/SWCNT-SA/KTP dual-loss-modulated Q-switched and mode-locked lasers have been studied, respectively. The main content of this dissertation is generalized as follows:I Using Nd:LuVO4crystal as laser media, passively QML Nd:LuVO4laser with GaAs and actively QML laser with AO modulator are demonstrated, respectively. Then the dual-loss-modulated QML lasers with AO and GaAs is realized, by inserting an AO modulator into the laser cavity, the stability of the QML laser is improved, the pulse width is compressed significantly and the peak power increases. Considering the influence of AO modulator, the rate equations for a diode-pumped dual-loss-modulated QML Nd:LuVO4laser can be obtained, the numerical solutions of the rate equations reproduce the laser characteristics well.(§2.2,§2.3,§2.4)Ⅱ The dual-loss-modulated QML intra-cavity frequency doubled Nd:GdVO4/KTP green laser with AO modulator and GaAs is realized in a Z-type cavity. The experimental results show that the Q-switched pulse energy and the peak power of the doubly QML laser are higher than those of the passively QML laser with only GaAs wafer. Considering the influences of AO modulator and KTP crystal, the rate equations for diode-pumped dual-loss-modulated QML Nd:GdVO4green laser with AO and GaAs are given. With the model, the numerical solutions of equations are in good agreement with the experimental results.(§2.5)Ⅲ By employing Cr4+:YAG as passive modulation, the output performances of AO/Cr4+:YAG dual-loss-modulated laser operating at1064nm and532nm with KTP as frequency doubling crystal are studied. The QML laser characteristics such as the pulse width, single-pulse energy etc. have been measured for different small-signal transmissions (To) of Cr4+:YAG, different reflectivity (R) of output coupler and modulation frequencies of the AO modulator (fp), the optimum output pulse can be obtained. By considering the influence of the AO modulator, a developed rate equation model for diode-pumped dual-loss-modulated QML green laser with AO modulator and Cr4+:YAG is presented. We also do numerically simulated evaluations to demonstrate the importance of considering the influence of the turnoff time, the simulation results show that the turnoff time is of great importance for the pulse energy and pulse width of the Q-switched pulse.(§3.1,§3.2)Ⅳ By employing four-mirror-folded cavity configration, dual-loss-modulated QML Nd:GdVO4laser at1.34μm with AO modulator and V3+:YAG is realized. Based on rate equation model for AO/Cr4+:YAG dual-loss-modulated QML laser, a developed rate equation model for AO/V3+:YAG dual-loss-modulation QML lasers is given and the numerical solutions are in good agreement with the experimental results.(§3.3)Ⅴ The QML performance in a diode-pumped Nd:Lu0.2Y0.8VO4laser with EO modulator and GaAs saturaber absorber is investigated. The QML laser characteristics such as the pulse width, pulse peak power etc. have been measured for different small-signal transmittance of GaAs, different reflectivity of output coupler and modulation frequencies of the EO modulator. Considering the influences of EO modulator, a developed rate equation model for the dual-loss-modulated QML laser with EO modulator and GaAs is proposed. With the model, the dynamic process of such lasers has been simulated.(§4.2)Ⅵ By simultaneously employing EO modulator and SESAM, stable sub-nanosecond pulse can be generated. The pulse width of the Q-switched envelope is shorter than the cavity roundtrip transmit time6.7ns. So there is only one mode-locked pulse in the Q-switched envelope and the repetition rate of the mode-locked pulse is equal to the modulation rate of EO modulator. The obtained peak power in this kind of laser is higher than those obtained in common QML lasers.(§4.3)Ⅶ Using Nd:YVO4, Nd:LuVO4, Nd:Lu0.2Y0.8VO4and Nd:Gd0.3Lu0.33Y0.37VO4crystals as laser media, AO/SWCNT-SA dual-loss-modulated QML laser is realized. The experiment results show the dual-loss-modulated QML Nd:Gd0.3Lu0.33Y0.37VO4laser can generate shorter pulse width and higher peak power in comparison with the Nd:LuVO4, Nd:YVO4, or Nd:Lu0.2Y0.8VO4lasers.(§5.1)Ⅷ The experimental studies on diode-pumped dual-loss-modulated QML Nd:Gd0.3Lu0.33Y0.37VO4laser with EO modulator and SWCNT-SA is carried out. The experimental results show that larger pulse energy and shorter pulse width can be obtained in the Nd:Gd0.3Lu0.33Y0.37VO4lasers than those obtained in former vanadate crystal lasers because of the inhomogeneous broadening of the fluorescence line widths and reduction of the stimulated emission cross-section.(§5.2)Ⅸ Using a three-mirror-folded cavity, the dual-loss-modulated QML intra-cavity frequency doubled Nd:Lu0.15Y0.85VO4/KTP green laser with AO modulator and SWCNT-SA is realized. In comparison with the solely passively QML green laser with SWCNT-SA, the dual-loss-modulated QML green laser can generate shorter pulse width of Q-switched envelope and higher average peak power, the stability of the QML laser is also significantly improved.(§5.3)The main innovations are generalized as follows:I Diode-pumped AO/GaAs dual-loss-modulated QML lasers operating at1064nm and532nm with KTP as frequency doubling crystal are firstly realized. In comparison with the solely passively QML laser with GaAs, the dual-loss-modulated QML laser can generate shorter pulse width of Q-switched envelope and higher pulse energy, the stability of the QML laser is also significantly improved. A developed rate equation model for the two kinds of dual-loss-modulated QML lasers is presented. With the model, the numerical simulations agree well with the experimental results.II The output performances of AO/Cr4+:YAG dual-loss-modulated laser operating at1064nm and532nm with KTP as frequency doubling crystal are studied for the first time. A developed rate equation model for diode-pumped dual-loss-modulated QML green laser with AO modulator and Cr4+:YAG is presented. We also firstly do numerically simulated evaluations to demonstrate the importance of considering the influence of the turnoff time.Ⅲ By employing V3+:YAG as saturaber absorber, we firstly realize dual-loss-modulated QML Nd:GdVO4laser at1342nm. In comparison with the single passively QML laser with V3+:YAG, the output characters of QML laser with the dual-loss-modulation are significantly improved. Based on rate equation model for AO/Cr4+:YAG dual-loss-modulated QML laser, a developed rate equation model for dual-loss-modulation QML lasers at1342nm is given for the first time.Ⅳ We firstly study the QML performance in a diode-pumped Nd:Lu0.2Y0.8VO4laser with EO modulator and GaAs. Considering the influences of EO modulator, a rate equation model is proposed for describing dual-loss-modulated QML laser with EO modulator and GaAs.Ⅴ Using EO modulator and SESAM as active and passive modulation, respectively, stable sub-nanosecond pulse can be generated. There is only one mode-locked pulse in the Q-switched envelope and the repetition rate of the mode-locked pulse is equal to the modulation rate of EO modulator. Compared with common lasers, the obtained peak power in this kind of laser is significantly improved.Ⅵ Using SWCNT as saturaber absorber, we have firstly studied AO/SWCNT-SA and EO/SWCNT-SA dual-loss-modulated QML laser at1064nm, as well as AO/SWCNT-SA/KTP dual-loss-modulated QML green laser at532nm, respectively. Shorter pulse width of Q-switched envelope, greater pulse energy and higher average peak power can be obtained.
Keywords/Search Tags:All-solid-state laser, Dual-loss-modulated, Q-switched and mode-locked, Intra-cavity frequency doubled, Rate equation model
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