Terada Yosuke, Miyasaka Kenji, Kondo Keisuke, Ishikura Norihiro, Tamura Takuya, Baba Toshihiko
Opt Lett. 2017 Nov 15;42(22):4695-4698. doi: 10.1364/OL.42.004695.
Silica-clad silicon photonic crystal waveguides (PCWs) are promising components for various applications because of their simple fabrication and generation of slow light. However, an optical loss higher than 4 dB occurs when they are simply coupled to input/output silicon wire waveguides. To reduce the optical loss, we proposed a junction structure in which light in the waveguide is first coupled to a high-group-velocity radiation mode at an expanded core and subsequently converted to the slow-light mode in a tapered core of the PCW. The coupling loss at a junction is calculated to be 0.28 dB at its minimum and less than 0.5 dB for the wavelength range of 12 nm. We measured a coupling loss of 0.46 dB for the device fabricated by the silicon photonics process. This low-loss junction well supports the practical use of PCWs.
二氧化硅包覆的硅基光子晶体波导（PCW）因其制造简单且能产生慢光，是适用于各种应用的有前景的组件。然而，当它们简单地与输入/输出硅线波导耦合时，会出现高于4 dB的光损耗。为了降低光损耗，我们提出了一种结结构，其中波导中的光首先在扩展芯处耦合到高群速度辐射模式，随后在PCW的锥形芯中转换为慢光模式。结处的耦合损耗计算得出，在其最小值时为0.28 dB，在12 nm波长范围内小于0.5 dB。对于通过硅光子学工艺制造的器件，我们测量到的耦合损耗为0.46 dB。这种低损耗结很好地支持了PCW的实际应用。
