低对比度光栅诱导的激光腔中准连续域束缚态研究

Low-Contrast Grating Induced Quasi Bound State in the Continuum of Laser Cavity

光子晶体等人工微结构中出现的连续域束缚态(BIC)处于光锥以上却不与背景泄漏模耦合,具有无限高的品质因数(Q值),构建在BIC或准BIC工作的激光器具有低阈值的优点。而低对比度光栅常用于低成本激光器的模式调制和耦出。针对激光器简化三层平板结构,提出利用上盖层刻蚀低对比度光栅诱导出Q值高达9.2×105的准BIC模式,并发现激光腔中模式的Q值对有源层的厚度变化相比上盖层光栅刻蚀深度的变化更敏感,且下盖层的厚度变化使Q值被周期性增强,准BIC的Q值可以被增强到9.66×106。研究结果对光栅基的低阈值电注入面发射激光器的设计具有指导意义。

The bound state in the continuum(BIC)found in artificial microstructures such as photonic crystals is located above the light cone but not couples with the background leakage modes,and therefore it has an infinite Qfactor,making lasers working at BICs or quasi-BICs have the advantage of low threshold.And low-contrast grating is often used in the mode modulation and out coupling of low-cost lasers.For the simplified three-layer slab structure of the lasers,it is proposed to induce a quasi-BIC with the Q factor of 9.2×105 by etching the lowcontrast grating(LCG)in the top cladding layer.Besides,it is found the thickness of active layer is more sensitive to quasi-BIC lasers than the depth of etched LCG,and the Q factor can be maximized periodically up to 9.66×106 with the increase of the thickness of bottom cladding layer.The results are instructive to the design of grating-based low threshold electrically injected surface-emitting lasers.