产生太赫兹波辐射的方法可分为电子学和光子学两大类。在光子学领域,非线性光学差频方法是获取高功率、低成本、便携式、室温运转太赫兹波的主要方法之一。实验研究了激光二极管(LD)端面抽运Nd:YAG 1319 nm/1338 nm双波长准连续线偏振运转激光器,理论计算了输出双波长在非线性晶体DAST(4-N,N-dimethylamino-4′-N′-methyl-stilbazolium tosylate)中差频产生太赫兹辐射的平均功率。在重复频率50 kHz时,双波长激光平均输出功率达到2.22 W,斜率效率12.72%,线偏振度0.983,脉冲宽度71.91 ns。M2因子仅为1.165,不稳定性小于0.487%。根据非线性差频理论,计算出可在1 mm厚DAST晶体中获得4.71 mW的3.23 THz高相干性太赫兹波辐射。这两条非常接近的谱线为进一步通过非线性光学差频方法获得高相干性太赫兹波提供了理论基础。

The methods to generate terahertz (THz) waves can be divided into electronics and photonics. We use nonlinear optical difference frequency generation to obtain THz waves which belongs to photonics method. It is portable and run at room temperature, with high power and low cost. A simultaneous dual-wavelength quasi-continuous wave (CW) laser-diode-end-pumped Nd:YAG laser polarized operating at 1319 nm and 1338 nm has been demonstrated and the laser at 1064 nm is suppressed successfully. A total polarized quasi-CW output power of 2.22 W is obtained at a pump power of 20 W with a pulse repetition rate of 50 kHz, and the slope efficiency is 12.72%. The corresponding pulse width is 71.91 ns. The beam quality factor M2 is as low as 1.165 and the instability of the output power is less than 0.487% at the polarized wave output power of 2.17 W. Using the simultaneous dual-wavelength laser, the highly coherent THz wave radiation of 3.23 THz will be generated by nonlinear optical difference frequency method in DAST (4-N,N-dimethylamino-4′-N′-methyl-stilbazolium tosylate) crystal. The ideal output peak power is 4.71 mW. The simultaneous dual-wavelength laser provides theoretically basis for generating highly coherent terahertz wave radiation by nonlinear optical difference frequency method.