Abstract-Two-Dimensional Multimode Terahertz Random Lasing with Metal Pillars

Yongquan Zeng, Guozhen Liang, Bo Qiang, Kedi Wu, Jin Tao, Xiaonan Hu, Lianhe H. Li, Alexander Giles Davies, Edmund H. Linfield, Hou Kun Liang, Ying Zhang, Yidong Chong,  Qi Jie Wang,

https://pubsdc3.acs.org/doi/10.1021/acsphotonics.8b00260

Random lasers employing multiple scattering and interference processes in highly disordered media have been studied for several decades. However, it remains a challenge to achieve broadband multimode random laser with high scattering efficiency, particularly at long wavelengths. Here, we develop a new class of strongly multimode random lasers in the terahertz (THz) frequency range in which optical feedback is provided by multiple scattering from metal pillars embedded in a quantum cascade (QC) gain medium. Compared with the dielectric pillars or air hole approaches used in previous random lasers, metal pillars provide high scattering efficiency over a broader range of frequencies and with low ohmic losses. Complex emission spectra are observed with over 25 emission peaks across a 0.4 THz frequency range, limited primarily by the gain bandwidth of the QC wafer employed. The experimental results are corroborated by numerical simulations which show the lasing modes are strongly localized.