摘要
对3.5μm KTiOAsO_(4)光参量振荡器(KTA-OPO)的温度调谐性能进行研究,仿真计算不同温度下KTA的相位匹配曲线,以及光束与z轴的夹角θ与调谐斜率的对应关系。仿真结果表明,随着θ值的增大,闲频光的峰值波长呈单调递增的趋势,调谐斜率呈单调递减的趋势,且I类相位匹配的调谐斜率普遍大于Ⅱ类。对于非临界相位匹配(NCPM)KTA-OPO,对其温度调谐性能进行理论和实验研究。实验结果表明,当温度从30℃升高到180℃时,在II类相位匹配的条件下,闲频光的峰值波长从3463nm移动到3474nm,调谐斜率为0.073nm/℃,理论上的调谐斜率为0.077nm/℃,实验与理论计算结果相符,说明非临界相位匹配KTA-OPO在不同温度下的中红外闲频光输出波长受到温度的影响小,环境适应性强。
Objective Lasers operated at 3.5μm stretch the absorption peaks in the C—H bonds and exhibit high transparency in the atmosphere windows,making the lasers that generate beams with frequencies of 3.5μm useful in applications using spectroscopy,remote sensing,environmental monitoring,and infrared(IR)countermeasures.Optical parametric oscillation(OPO)is an effective method to radiate mid-IR laser beams that can transform near-IR lasers into mid-and far-IR radiation.The KTiOAsO_(4)(KTA)crystal is a member of the KTiOPO_(4)(KTP)crystal family and an excellent nonlinear material.The spectroscopy transmittance range of KTA is 0.35--5.30μm.The absorption loss in KTA crystals in the 3--5μm bandwidth is much lower than that of the KTP crystal.The KTA crystal has a large nonlinear coefficient,a wide-angle and temperature-matching bandwidth,a high damage threshold,and stable physical and chemical properties.Experiments on noncritical phase matching(NCPM)demonstrated that the KTA optical parametric oscillator(OPO)pumped by a Nd∶YAG 1064-nm laser can radiate a 3.5-μm laser beam.Due to the influence of temperature dispersion,the wavelength value of KTA-OPO changes as a function of temperature.The detailed study of KTA-OPO temperature tuning properties presented herein can guide the application of KTA-OPO lasers.To date,there are few theoretical or experimental studies concerning the temperature tuning performance of KTA-OPO.Methods Temperature tuning properties of KTA-OPO are studied theoretically and experimentally.Based on the normal temperature dispersion equation and the temperature dispersion equation of the KTP crystal,the temperature tuning properties of KTA-OPO at different cutting angles(θ)are calculated.The wavelength of idle light(λi)at T=25℃and the temperature tuning slope(Δλi/ΔT)of KTA-OPO at different cutting angles are calculated with an accuracy of 1°when the wavelength of the pump laser is set at 1064 nm.An experimental study using a 3.5-μm NCPM KTA-OPO laser pumped by a Nd∶YAG 1064 nm laser is conducted.The pump source is an SL800 series pulsed Nd∶YAG laser with a pulse width of 13 ns,a spot diameter of 8 mm,and a repetition rate of 1 Hz.A small hole is placed behind the laser for dimming,and the spot diameter is compressed to 4 mm using a telescope system to increase the energy density of the pump laser.The temperature of the KTA crystal is controlled in a temperaturecontrolled furnace with an accuracy of 0.1℃.The wavelengths of the KTA-OPO idlers at 30,80,130 and 180℃are measured using an Omni-300λspectrometer(Zolix Instruments Co.,Ltd)with an accuracy of 1 nm.At the back end of the grating spectrometer,a DEC-M204-InSb detector and a ZAMP amplifier(Zolix Instruments Co.,Ltd)are used to detect and amplified the laser signal at the specified transmission wavelength.A DSOX3054 Toscilloscope is used to display and measure the signal amplitude from the ZAMP amplifier.The value of the maximum wavelength of the laser signal is set equal to the peak wavelength of the output idler by the grating spectrometer.Results and Discussions The temperature tuning properties of KTA at differentθangles and the OPO pumped by a 1064-nm laser are studied(Fig.1).Comparison of the laser wavelength andΔλi/ΔT of the idler at differentθangles revealed that the wavelength of the idler increased monotonically as the value ofθincreased,whileΔλi/ΔT decreased monotonically(Fig.2).When the temperature is 30,80,130,and 180℃,the measured values ofλi are3463,3466,3469,and 3474 nm,respectively,andΔλi/ΔT is 0.073 nm/℃.The experimental results show that the wavelength of the output idler of KTA-OPO(θ=90°andΦ=0°)is less affected by changes in temperature under conditions of typeⅡphase matching,which confirms the theoretical conclusions(Fig.4).The results demonstrate that the temperature dispersion equation(Table 1)can be extended from near-IR to mid-IR band spectroscopy.Conclusions The laser wavelength value of KTA-OPO is relatively stable at different temperatures.In typeⅠandⅡphase matching,with the increase ofθ,the idler wavelength value increased monotonically,butΔλi/ΔT decreased monotonically and ranged from to 0.0774 to 1.4968 nm/℃.TheΔλi/ΔT value of the typeⅠphase matching KTAOPO is generally larger than theΔλi/ΔT value of the typeⅡphase match.Among all phase matching points for angleθ,the temperature tuning range is smallest whenθ=90°under typeⅡphase matching,and the theoretical value ofΔλi/ΔT is 0.0774 nm/℃.The experimental results are consistent with the theoretical calculations.Both theoretical and experimental studies show that the wavelength of the mid-IR laser beam of the NCPM KTA-OPO is less affected by temperature.This results of this study demonstrate the potential application of KTA-OPO pumped by a 1064-nm laser.
作者
卞进田
孔辉
徐海萍
叶庆
孙晓泉
Bian Jintian;Kong Hui;Xu Haiping;Ye Qing;Sun Xiaoquan(State Key Laboratory of Pulsed Power Laser Technology,College of Electronic Countermeasure,National University of Defense Technology,Hefei Anhui 230037 China;Advanced Laser Technology Laboratory of Anhui Province,National University of Defense Technology,Hefei Anhui 230037 China)
出处
《中国激光》
EI
CAS
CSCD
北大核心
2021年第4期249-255,共7页
Chinese Journal of Lasers
基金
脉冲功率激光技术国家重点实验室主任基金(SKL2019ZR06)。
