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Research on 1.94μm TM:YAP Laser and In-band Pumped HO:YLF Laser

Author: YinWeiWen
Tutor: YaoBaoQuan
School: Harbin Institute of Technology
Course: Physical Electronics
Keywords: 2-μm solid-state laser in-band pump Ho:YLF Tm:YAP
CLC: TN248.1
Type: Master's thesis
Year: 2011
Downloads: 45
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Abstract


2μm Ho laser can be applied in many fields, such as therapy, coherent Doppler radar and intermediate infrared OPO. Because the absorption cross section of Ho in the waveband of commercial diode laser is small, people used Tm3+ to sensitize Ho3+ and realised Ho laser emission. This method can result in much heat load inside the crystal at room temperature, which make the laser efficiency decrease. In contrast, Ho:YLF laser in-band pumped by Tm laser can operate at high power at room temperature.Theoretically, the level transition theory of Tm and Ho is analyzed. From the rate equation, the calculation method of laser power is derived which include ground-state loss and up-conversion loss. And we use the method to establish a model of Ho laser. Then the temperature distribution inside the crystal is taken to consideration, the spatial distribution of Boerziman factor is obtained.Experimentally, first we use fiber-coupled laser-diode with center wavelength of 795nm to pump single Tm:YAP crystal. 10W power is obtained when LD power reachs 41.5W with slope efficiency of 34%; Then in the two Tm:YAP crystal experiment, we use a flat mirror as the high reflectivity mirror of the resonator firstly, the effects of cavity length and transmittance of the output coupler are investigated, we realize 23.4W output power in the best case with center wavelength of 1.99μm. Then we use the volume Bragg grating （VBG） as the resonator, a Fabry-Perot etalon is added at the same time, finally we obtain the maximum output power of 20W, centry wavelength of 1940nm,π-polarized laser. The beam quality factor M2 is about 2.2 measured at 10W.Subsequently,the Ho:YLF laser experiment is developed. The Ho:YLF crystal is a-cut,32mm in length and doping concentration 0.5at.%. In the CW laser experiment,we investigate the effects of cavity length,transmittance and temperature. We obtain 9.5W, 2065nm,π-polarized output laser. In the acousto-optic Q-switch experiment, the laser operates at pulse repetition frequency of 10kHz and 20 kHz. At 10kHz, the maximum single pulse energy is 0.69mJ, pulse width is 175ns.

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CLC: > Industrial Technology > Radio electronics, telecommunications technology > Photonics technology,laser technology > Laser technology, the maser > Laser > Solid-state lasers
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