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Study On Characteristics Of All-solid-state Multi-wavelength Laser

Posted on:2009-11-02Degree:DoctorType:Dissertation
Country:ChinaCandidate:X W FanFull Text:PDF
GTID:1118360242495036Subject:Optics
Abstract/Summary:PDF Full Text Request
Compared with traditional lasers, diode-pumped solid-state lasers (DPSSL) have obvious advantages including simplicity, high efficiency, compactness, high stability, high beam quality and long lifetime. With the development of high power laser diode, new laser crystals, nonlinear optical crystals, optical superlattice with quasi-phase-match and the maturation of optical frequency conversion technology all-solid-state laser has become a central of focus in the field of laser. Simultaneous emission at multiple wavelengths capable from one single laser crystal has been of interest for its special properties and the practical application in various fields, such as resonance holographic interferometer, precision laser spectroscopy, lidar, multiphoton dissociation of molecules, isotope separation, nonlinear optical frequency conversion, medical applications, laser display and military. All-solid-state ultraviolet lasers have wide applications in the fields such as optical data storage, precise materials making, mold fabrication, optical printing, medical treatment, spectroscopic analysis and scientific research and also have been paid much attention on.In this dissertation, the performance of a dual-wavelength continuous wave (cw) diode-end-pumped Nd:YVO4 laser that generates simultaneous laser action at the wavelengths 1064nm and 1342nm has been investigated from both theoretical and experimental ways. The study on the diode-end-pumped Nd:YVO4 acousto-optical Q-switch (AO) dual-wavelength laser at 1342nm and 1064nm has been carried out. The results of research on an intermittent oscillation dual-wavelength diode-side-pumped Nd:YAG laser operated at 1319nm and 1064nm has been present. By using a single periodically poled LiTaO3 (PPLT), cascaded structure superlattice as the frequency conversion material, an all-solid-state UV (411nm) and red (671nm) dual-color laser has been set up. The operating characteristic of a compact 335.5nm source based on frequency quadrupling of a diode-end-pumped Q-switched Nd:YVO4 laser at 1342nm has been studied. The main content of this dissertation includes:1. The theoretical dependence of the relative thermally induced diffraction loss arising from thermal effect of the laser crystal on the absorbed pump power, focus position of pumping light and the beam waist of the laser cavity mode has been investigated. Considering the spatial variation of both the pump rate and the dual-wavelength cavity field, a rate equation model describing an ideal four-level laser that generates cw dual-wavelength simultaneous laser action has been established. On the basis of the space-dependent rate equation analysis, the output coupling rate forĪ»1 as the function of the output coupling rate forĪ»2 has been derived when the laser was operation at dual-wavelength under given pumping condition. The influences of the focus position of pumping light on the competitive ability of the dual-wavelength and the performance of the dual-wavelength laser at different pump level have been studied. A dual-wavelength cw diode-end-pumped Nd:YVO4 laser that generates simultaneous laser action at the wavelengths 1064nm and 1342nm by use of a two-mirror cavity and a three-mirror cavity has been set up, respectively. Using the space-dependent rate equations, the simulations about the experimental results have been performed.2. Considering the influences of the thermally induced diffraction losses and the turn-off time of AO Q-switch on the dual-wavelength pulse, a rate equation model describing the actively Q-switched laser with AO modulator has been established. AO Q-switched dual-wavelength operation of a diode-end-pumped Nd:YVO4 laser at the wavelengths 1064nm and 1342nm by use of a two-mirror cavity and a three-mirror cavity has been realized, respectively. At given repetition rates, the dependence of the average output power, the pulse width and pulse distance of the dual-wavelength on the pump power and the dependence of the average output power of the dual-wavelength on the focus position of pumping light have been measured. Using the rate equations, the simulations about the experimental results have been performed.3. An alternately intermittent oscillation technique was proposed, by using a single pump source, a Y cavity, a single active medium and two AO Q-switches, the population inversion was distributed efficiently, the competitive interaction of the two laser lines can be avoided and the stable output of dual-wavelength was easily obtained. The technique is to achieve dual-wavelength intermittent oscillation by controlling the delay time of the AO-2 relating to the AO-1. Because the delay time of the Q-switch can be adjusted continuously, so the ratio of the output power for two wavelengths can be controlled by adjusting the delay time. An intermittent oscillation dual-wavelength diode side-pumped Nd:YAG laser has been set up and the dependence of the average output power, the pulse width of the dual-wavelength on the delay time have been measured at given repetition rates and pump power. Basing on the rate equations theory, the rate equations model of the intermittent oscillation dual-wavelength laser describing an ideal four-level has been established and the numerical simulation has been performed.4. Basing on the photodynamic therapy theory for diagnosing and treating malignant tumors, an all-solid-state laser scheme that simultaneously generates red at 671nm and ultraviolet at 411nm by using a single PPLT, cascaded structure superlattice as the frequency conversion material was proposed. A PPLT crystal consisting of two segments in series forming a cascaded structure and having six parallel channels has been designed and fabricated by using the conventional electrical poling technique at room temperature. The simultaneous dual-wavelength operation at 1064 nm and 1342nm with the optimal spatial overlap was achieved by using two fiber-coupled laser-diodes pumping two Nd:YVO4 crystals, then simultaneous generation of red at 671 nm and UV at 411 nm has been realized basing on single-pass quasi-phase-matched (QPM) second harmonic generation (SHG) and sum-frequency mixing (SFG) processes in the PPLT.5. The properties of several ultraviolet nonlinear optical crystal materials have been systematically analyzed. The experimental studies on the cw and Q-cw operating characteristics of the diode-end-pumped Nd:YVO4 1342nm laser has been carried out. By using KTP crystal as intracavity frequency doubling crystal, the performance of a diode-end-pumped Q-switched Nd:YVO4 671nm laser has been experimentally investigated, then LBO (BBO) crystal was exploited for the subsequent external fourth harmonic generation (FHG) and the UV output at 335.5nm was obtained. A comparative study of LBO and BBO crystal for FHG has been conducted. With a 6.3 W of absorbed pump power and 10 kHz of frequency repetition rates, the UV output power of 35mW and 63mW have been obtained by using LBO and BBO as frequency quadrupling nonlinear crystal, respectively.6. The methods of achieving red, green and blue laser output simultaneously and the main development have been summarized. A new method achieving high power and stable red, green, blue simultaneous output and so as to white light output by using an all-solid-state intermittent oscillation dual-wavelength laser as fundament lights and using optical superlattice or nonlinear optical crystal as the frequency conversion material has been proposed.
Keywords/Search Tags:All-solid-state, dual-wavelength laser, intermittent oscillation, PPLT, BBO, LBO, 335.5nm
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