Zhan Biyan, Zhang Haoxuan, Liu Xianwen
Opt Express. 2025 Mar 10;33(5):11221-11230. doi: 10.1364/OE.547934.
Grating couplers typically encounter minimum feature size (MFS) constraints in fabrication. To address this issue, we incorporated user-defined apodization profiles into the inverse design process to enhance conversion efficiency (CE). We optimized grating parameters based on lithium-niobate on insulator (LNOI) platforms. With a single-step lithography and etching process, we achieved a remarkable peak CE of -1.97 dB at an MFS of 200 nm in the telecom C-band. This result surpasses previous LNOI designs that lack complex structures, such as bottom metal reflectors or overlaid materials, offering a more straightforward path for developing high-efficiency LNOI grating couplers. Leveraging this design strategy, we also demonstrated a broadband grating coupler with a peak CE of -3.22 dB and 3-dB bandwidth over 106 nm.
光栅耦合器在制造过程中通常会遇到最小特征尺寸（MFS）的限制。为了解决这个问题，我们在逆向设计过程中纳入了用户定义的变迹轮廓，以提高转换效率（CE）。我们基于绝缘体上铌酸锂（LNOI）平台优化了光栅参数。通过单步光刻和蚀刻工艺，我们在电信C波段200纳米的最小特征尺寸下实现了-1.97分贝的显著峰值转换效率。这一结果超越了以往缺乏复杂结构（如底部金属反射器或覆盖材料）的LNOI设计，为开发高效LNOI光栅耦合器提供了一条更直接的途径。利用这种设计策略，我们还展示了一种宽带光栅耦合器，其峰值转换效率为-3.22分贝，3分贝带宽超过106纳米。
