9:45 AM - 10:00 AM
[22a-S621-4] Freely-bent waveguide and channel drop filter realized by coupled L2 nanocavities
Keywords:photonic crystal,optical cavity,silicon photonics
We report realization of freely-bent waveguides in 2D triangular lattice photonic crystal slab by highly-dense curved coupled resonator optical waveguides (CROWs). The Si air-bridge photonic crystal had lattice constant, hole radius, and slab thickness of 410 nm, 100 nm, and 200 nm, respectively. L2 nanocavity used here has small footprint and a high loaded Q factor (~0.6 million) and fundamental cavity wavelength of ~1537 nm. As reported previously (Kuramochi et al., JSAP 2015 fall 16a-2A-10), short period L2 CROW slanted from Γ-K orientation forms broad CROW bands. We fabricated curved CROW according to two connected semicircles (radius: 4.8 μm) formed by 26 L2 nanocavities and total length of ~30 μm. In this curved CROW, cavity spacing is not constant. As shown in Fig. 1, ~55nm-wide CROW band with fairly high transmission was obtained. Next, we report realization of channel drop filter formed by a L0 nanocavity and two semicircular L2 CROWs. The former has a fundamental cavity mode with loaded Q of ~106 and wavelength of ~1520nm and was significantly detuned from L2 nanocavities forming CROWs. Through the fundamental cavity mode of L0, successful drop operation was demonstrated as shown in Fig. 2. By changing the distance between the L0 nanocavity and CROWs, Q factor was adjusted to 30,000 and 230,000. Thus, we can design channel drop filter by combination of nanocavity and curved CROWs as well as that of nanocavity and straight line-defect waveguides. In conclusion, we have reported freely-bent curved CROW which has a wide bandwidth, compatible with triangular lattice photonic crystal, and highly integratable with high-performance nanocavity devices. We reveal that a CROW behaves as normal waveguide for any nanocavities which can be coupled to.