提出了基于正交光注入增益开关850 nm垂直腔面发射激光器(850 nm-VCSEL)获取梳距可调双路宽带光学频率梳(OFC)的方案,通过数值仿真研究了系统参量对OFC性能的影响。在该方案中,首先采用大信号电流调制850 nm-VCSEL使其呈增益开关状态,此时Y偏振分量激射并呈周期脉冲状态,而X偏振分量被抑制,可以获得一路偏振沿Y方向的OFC(Y-OFC);进一步引入偏振方向沿X方向的注入光(即正交光注入),在合适的注入参数条件下,增益开关850 nm-VCSEL中的X偏振分量被激射并呈周期脉冲动力学状态,且输出的X偏振分量具有与Y偏振分量强度相当的光谱分布,从而可以获得两路正交的OFC。数值仿真的结果表明:受到调制频率fm=4.2 GHz、调制深度m=0.75的大信号电流调制的850 nm-VCSEL,在频率失谐Δv=10.0 GHz的正交光注入下,通过选取合适的注入光场振幅Einj可使激光器输出带宽(功率变化在10 dB范围内)超过105.0 GHz的双路宽带OFC。借助于正交光注入下增益开关850 nm-VCSEL输出的X偏振分量和Y偏振分量的光谱分布,确定了获得双路OFC所需的Einj和Δv的范围。最后,通过分析其他调制频率下所获取的OFC性能,论证了该方案产生双路宽带OFC梳距的可调谐性。

In this study, we propose a scheme to generate tunable and broadband two-channel optical frequency comb (OFC) based on a gain-switched 850 nm vertical-cavity surface-emitting laser (850 nm-VCSEL) under orthogonal optical injection. In addition, the influences of some operation parameters on the performances of the generated OFC are numerically investigated. For developing this scheme, an 850 nm-VCSEL is modulated using a large signal current and is subsequently driven into a gain-switching state. In this case, the Y polarization component of the laser oscillates and behaves in a periodic pulse state, whereas the X polarization component is suppressed. Therefore, a one-channel OFC is generated in the Y polarization direction (Y-OFC). The X polarization component of the gain-switched 850 nm-VCSEL can be oscillated to achieve a periodic pulse state with a spectral intensity equivalent to that of the Y polarization component by introducing optical injection polarizing along the X direction (orthogonal optical injection). Thus, a two-channel OFC can be obtained. The simulated results are obtained based on an 850 nm-VCSEL under current modulation with a modulation depth of m=0.75 and a modulation frequency of fm=4.2 GHz as well as orthogonal optical injection with frequency detuning of Δv=10.0 GHz; these results indicate that a two-channel OFC having bandwidths of greater than 105.0 GHz with an amplitude variation of less than 10 dB can be obtained under the optimized injected field amplitude Einj. Subsequently, the ranges of Einj and Δv are determined by examining the optical spectra of the X and Y polarization component outputs obtained from the gain-switched 850 nm-VCSEL subjected to orthogonal optical injection for obtaining a two-channel OFC. Finally, the tunability of comb spacing is demonstrated by analyzing the OFC performance under different values of fm.