An integrated-optics, flat-top drop-filter with low excess loss, and high sidelobe suppression ratio (SLSR), is demonstrated. The filter is based on apodized multimode waveguide Bragg grating (AMWBG) developed on a silicon-on-insulator (SOI) platform. Antisymmetric periodic refractive-index perturbations are imposed on both sides of the waveguide to couple light contra-directionally between the fundamental (TE0) and the first-order transverse electric modes (TE1). To achieve a Gaussian apodization profile, the lateral-misalignment between the two sides of the waveguide is modulated by adjusting the positions of both sides of the grating features in a complementary manner. In this way, the undesired phase errors, which exist in conventional misalignment-modulated Bragg gratings and distort the grating responses, can be eliminated. Experimental results show that our AMWBG has a high-quality flat-top response, a high SLSR of >21 dB, a 3-dB bandwidth of 8 nm, a low excess loss of 0.24 dB, and a high roll-off rate at the filter edge. We also demonstrate a dual-stage filter that has a flat-top, drop-port response with a 3-dB bandwidth > 7.5 nm, a SLSR >40 dB, and an excess loss<0.5 dB.

中文翻译：

---

基于互补未对准多模波导布拉格光栅的光谱无失真、平顶、下降滤波器

展示了一种具有低过量损耗和高旁瓣抑制比 (SLSR) 的集成光学平顶下降滤波器。该滤波器基于在绝缘体上硅 (SOI) 平台上开发的切趾多模波导布拉格光栅 (AMWBG)。反对称周期性折射率扰动施加在波导的两侧，以在基波 (TE0) 和一阶横向电模式 (TE1) 之间反向耦合光。为了实现高斯切趾轮廓，通过以互补方式调整光栅特征两侧的位置来调制波导两侧之间的横向错位。通过这种方式，可以消除传统未对准调制布拉格光栅中存在的不希望有的相位误差并使光栅响应失真。实验结果表明，我们的 AMWBG 具有高质量的平顶响应、> 21 dB 的高 SLSR、8 nm 的 3-dB 带宽、0.24 dB 的低过量损耗和高滚降率过滤边缘。我们还展示了一个双级滤波器，它具有平顶、分流端口响应，带宽为 3dB > 7.5 nm，SLSR > 40 dB，额外损耗 <0.5 dB。