Gong Chen, Kawayama Iwao, Murakami Hironaru, Teramoto Takahiro, Tonouchi Masayoshi
Institute of Laser Engineering, Osaka University, Osaka, 565-0871, Japan.
Graduate School of Energy Science, Kyoto University, Kyoto, 606-8501, Japan.
Sci Rep. 2021 Jan 12;11(1):498. doi: 10.1038/s41598-020-80105-7.
Powerful, broadband terahertz (THz) pulses and its application attract an exponential growth of interests. Dual-color laser filamentation in gases is one of the promising THz sources because of the scalability of the THz energy and wavelength with input parameters. But the additional phase induced by the nonlinearities associated with high intensities cannot be neglected because it may result in modulation of the THz waves. We investigate the influences of the infrared pump energy and air dispersion on the terahertz generation in dual-color laser filament. We observe that optimum dual-color laser relative phase of the THz generation undergoes a linear shift with increasing pump energy due to the intensity-induced refractive index change. This phase shift is verified by the spectral broadening of a two-color laser affected by the same mechanism. The result improves our understanding of the theoretical framework for a higher power THz source.
强大的宽带太赫兹（THz）脉冲及其应用引起了人们兴趣的指数级增长。气体中的双色激光丝是有前景的太赫兹源之一，因为太赫兹能量和波长可随输入参数进行扩展。但是与高强度相关的非线性所引起的附加相位不可忽略，因为它可能导致太赫兹波的调制。我们研究了红外泵浦能量和空气色散对双色激光丝中太赫兹产生的影响。我们观察到，由于强度引起的折射率变化，太赫兹产生的最佳双色激光相对相位随泵浦能量增加而发生线性偏移。受相同机制影响的双色激光的光谱展宽验证了这种相位偏移。该结果增进了我们对更高功率太赫兹源理论框架的理解。
