Manipulating the coupling coefficient at subwavelength scales provides an additional degree of freedom in designing integrated Bragg gratings. We demonstrate asymmetric contradirectional couplers (contra-DCs) using sidewall-corrugated subwavelength grating (SWG) waveguides for broadband add–drop Bragg filters. We show that a SWG can effectively increase the overlap of coupled modes and thus the photonic band gap. The measured spectra show good agreement with the prediction of photonic band structure simulations. A record bandwidth of 4.07 THz (33.4 nm) has been achieved experimentally. A four-port Bragg resonating filter made of a phase-shifted Bragg grating SWG contra-DC is also demonstrated for narrow-band (near 100 GHz) filtering. All these devices are achieved on the 220-nm silicon-on-insulator platform with a compact length of less than 150 μm. These large stopband filters may find important applications such as band splitting, reconfigurable channel band switching, bandwidth-tunable filtering, and dispersion engineering.

中文翻译：

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适用于大型阻带滤波器的亚波长光栅双向耦合器

在设计集成的布拉格光栅时，在亚波长范围内操纵耦合系数可提供额外的自由度。我们演示了使用侧壁波纹亚波长光栅（SWG）波导进行宽带分插布拉格滤波器的非对称对向耦合器（contra-DC）。我们表明，SWG可以有效地增加耦合模式的重叠，从而增加光子带隙。测得的光谱与光子能带结构模拟的预测显示出良好的一致性。实验上已达到4.07 THz（33.4 nm）的记录带宽。还展示了由相移布拉格光栅SWG相反DC制成的四端口布拉格谐振滤波器，用于窄带（接近100 GHz）滤波。所有这些器件都是在220 nm绝缘体上硅平台上实现的，紧凑长度小于150μm。这些大型阻带滤波器可能会发现重要的应用，例如频带分割，可重新配置的通道频带切换，带宽可调的滤波和色散工程。