Pinto Tomás H P, Kirkbride James M R, Ritchie Grant A D
Opt Lett. 2018 Apr 15;43(8):1931-1934. doi: 10.1364/OL.43.001931.
We report on the broadening of the optical bandwidth of a distributed feedback quantum cascade laser (QCL) caused by the application of radio frequency (RF) noise to the injection current. The broadening is quantified both via Lamb-dip spectroscopy and the frequency noise power spectral density (PSD). The linewidth of the unperturbed QCL (emitting at ∼5.3 μm) determined by Lamb-dip spectroscopy is 680±170 kHz, and is in reasonable agreement with the linewidth of 460±40 kHz estimated by integrating the PSD measured under the same laser operating conditions. Measurements with both techniques reveal that by mixing the driving current with broadband RF noise the laser lineshape was reproducibly broadened up to ca 6 MHz with an increasing Gaussian contribution. The effects of linewidth broadening are then demonstrated in the two-color coherent transient spectra of nitric oxide.
我们报告了通过向注入电流施加射频（RF）噪声导致分布式反馈量子级联激光器（QCL）的光带宽展宽的情况。通过兰姆凹陷光谱法和频率噪声功率谱密度（PSD）对展宽进行了量化。通过兰姆凹陷光谱法确定的未受扰动的QCL（发射波长约为5.3μm）的线宽为680±170kHz，与在相同激光工作条件下通过积分测量的PSD估计的460±40kHz线宽合理一致。两种技术的测量结果都表明，通过将驱动电流与宽带RF噪声混合，激光线形可重复展宽至约6MHz，且高斯贡献增加。然后在一氧化氮的双色相干瞬态光谱中展示了线宽展宽的影响。
