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Study Of Diode Pumped Tm3+ Doped Solid State Lasers

Posted on:2009-02-17Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y F LiFull Text:PDF
GTID:1118360278461984Subject:Physical Electronics
Abstract/Summary:PDF Full Text Request
Widely applicable mid-infrared laser sources become more and more important in laser remote sensing, laser target detecting, spectra analysis, atmospheric environment monitoring, space communicating and special military applications. Emission wavelength of Tm laser system is near 2μm, just within atmospheric window, it provides an effective tool for remote sensing and photoelectric countermeasures. Tm laser is thought to be an ideal laser source for coherent Doppler lidar, differential absorption lidar (DIAL) and laser ranging and tracking system. In addition, Tm laser is an ideal pump sources for optical parameter oscillator (OPO) in the 35μm band. This thesis investigates and explores four diode-end-pumped thulium-doped lasers theoretically and experimentally.As the basis of J-O theory calculation and Tm laser experiments, the absorption and emission spectrum of Tm:GdVO4 and Tm:YAP in the infrared visible and ultraviolet band are measured, the distribution and lifetime of thulium energy levels are also given. According to experimental data, the absorb cross section, emission cross section and effective emission cross section are calculated. Compared with the spectra properties of Tm:LuAG and Tm:YAG, the distribution and transition of Tm3+ energy levels in different single crystals are discussed.In theoretical aspects, we mainly calculate the optical parameters of Tm3+ in different materials and build the end-pumped quasi-three-level mode of Tm laser system. First of all, according to the absorption and emission spectrum data, we calculate the intensity parameters of Tm3+ in GdVO4 and YAP single crystals, and then the spectral parameters (Spontaneous emission transition rate, radiative lifetime, fluorescence branching ratio and integrated emission cross section) between the exited state and the lower state are given. The problem of which crystal and which level of Tm3+ is probable for laser emission is analyzed theoretically, the upconversion process and intensity detected in visible band are explained appropriately. Secondly, After getting the transition and energy transfer process of Tm3+ levels and considering the influence of upconversion and grand state dissipaton, we build the end-pumped quasi-three-level mode of Tm laser system. The equation between input power and output power is analyzed, the length of crystal, the concentration of Tm3+ and output coupler that contribute to the change of output power are given. The relationship between energy per q-switch pulse and modulate frequency are discussed with different uplevel lifetimes. At last, In different Tm laser operation modes, the frequency selective property and line width compression property of F-P etalon double-cavity and birefringence(BF) are analyzed. In addition, the temperature gradient of Tm:GdVO4 and Tm:YAP crystal and the sympathetic vibration frequency of experimental platform are calculated by ANSYS software.In experimental aspects, we mainly make comparative study of Tm lasers in different operation modes such as single frequency, tunable, Q-switch and so on. All of these results supply the important reference data to how to selected Tm crystals in different application directions. First of all, single frequency Tm:GdVO4, Tm:YAP,Tm:YAG and Tm:LuAG microchip lasers are proved and get detailed comparison. Single frequency Tm lasers are achieved by F-P etalon and double-cavity methods, widely tunable single frequency Tm:YAP laser with etalons and BF in the cavity is proved. Secondly, High power Tm:GdVO4, Tm:YAP, Tm:YAG and Tm:LuAG lasers operating at continue-wave, widely tunable contimuewave and acousto-optic q-switch modes are compared and analyzed. The factors that affect output power such as crystal material, crystal quality, output coupler, crystal length and temperature control are also given. The thermal focal lengths of crystals are measured. In condition of q-swtich pulse output, the relationship among pump power, modulate frequency and pulse width is measured and discussed. Finally, a preliminary experiment of seed injected ring cavity Tm laser is proved and it gives reference data for the later laser system design and build.
Keywords/Search Tags:Diode-Laser pump, 2μm Tm laser, absorption and emission, thulium doped single crystal, acousto-optic Q-swtich
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