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ZGP 晶体是正单轴晶体(
${n_\rm {e}} > {n_\rm {o}}$ ),三波耦合过程中,Ⅰ类相位匹配条件可写为:$$ \dfrac{{n_p^\rm {o}}}{{{\lambda _p}}} = \dfrac{{n_s^\rm {e}(\theta )}}{{{\lambda _s}}} + \dfrac{{n_i^\rm {e}(\theta )}}{{{\lambda _i}}} $$ (1) ZGP的e光折射率公式及Sellmeier方程[12]如下:
$$ n_{\rm e}^2(\theta ) = \frac{{n_{\rm o}^2n_{\rm e}^2}}{{n_{\rm o}^2{{\sin }^2}\theta + n_{\rm e}^2{{\cos }^2}\theta }} $$ (2) $$ n_{\rm o}^2 = 8.040\;9 + \frac{{1.686\;25{\lambda ^2}}}{{{\lambda ^2} - 0.408\;24}} + \frac{{1.288{\lambda ^2}}}{{{\lambda ^2} - 611.05}} $$ (3) $$ n_{\rm e}^2 = 8.092\;9 + \frac{{1.864\;9{\lambda ^2}}}{{{\lambda ^2} - 0.414\;68}} + \frac{{0.840\;52{\lambda ^2}}}{{{\lambda ^2} - 452.05}} $$ (4) 同时,三波相互作用需要满足能量守恒条件:
$$ \frac{1}{{{\lambda _p}}} = \frac{1}{{{\lambda _s}}} + \frac{1}{{{\lambda _i}}} $$ (5) 由以上方程,结合文中实验,计算泵浦光为2128 nm时,ZGP的Ⅰ类相位匹配曲线如图1所示。由图1可以看出,当ZGP相位匹配角度改变时,其输出信号光和闲频光的波长也随之改变。由以上方程也可以看出,当其他条件不变,泵浦波长改变时,信号光和闲频光的波长也随之改变,其仿真图在第2.3.2节实验分析部分一并给出。
Experimental study on tunable characteristics of optical parametric oscillator based on ZnGeP2 in long-infared dual-band
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摘要: 文中报道了一种基于ZnGeP2 (ZGP) 的纳秒宽调谐长波红外光参量振荡器(optical parametric oscillation, OPO)。采用重复频率50 Hz、脉冲宽度小于10 ns的1064 nm基频光泵浦基于Ⅱ类相位匹配KTP的光参量振荡器产生2.1 μm激光,进而泵浦基于Ⅰ类相位匹配的ZGP光参量振荡器产生7~11 μm长波红外输出。通过对ZGP的角度调谐获得了2.815~2.963 μm连续可调谐信号光,对应闲频光波长连续可调谐范围为7.82~9.08 μm。通过泵浦波长调谐的方式,当采用2107.13~2153.95 nm范围内的激光泵浦ZGP-OPO,获得了信号光波长范围为2.624~2.662 μm和2.745~2.956 μm的连续可调谐输出,对应闲频光范围为7.94~9.07 μm和10.20~10.82 μm。闲频光波长为8.03 μm、能量为0.8 mJ时,ZGP-OPO的泵浦光至闲频光转换效率9.4%。Abstract: A widely tunable long-infrared optical parametric oscillator (OPO) based on ZnGeP2 (ZGP) with nanosecond pulses output in dual bands was reported in this paper. As a fundamental laser of ZGP-OPO, KTP- OPO of 2.1 μm based on type Ⅱ phase match was pumped by 1064 nm fundamental delivering <10 ns pulses at 50 Hz. Furthermore, the ZGP-OPO of 7-11 μm based on type Ⅰ phase match was designed. Continuous-tunable signal wavelengths of 2.815-2.963 μm corresponding idle wavelengths of 7.82-9.08 μm was obtained using angle tuning of ZGP. Continuous-tunable signal wavelengths of 2.624-2.662 μm and 2.745-2.956 μm, which correspond the idle wavelengths of 7.94-9.07 μm and 10.20-10.82 μm respectively , were obtained using pump wavelengths tuning. The single-pulse energy was 0.8 mJ at 8.03 μm, pump to idler conversion efficiency was 9.4%.
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Key words:
- optical parametric oscillation /
- long-infrared laser /
- continuous-tunable /
- dual-band
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