[19p-C301-1~17] 3.11 フォトニック構造・現象

▲ [19p-C301-17] Design of 2D Si photonic nanocavity with InP nanowire for current injection at the telecom band

〇(B)Edward Chen²、Masato Takiguchi^1,2、Shota Kita^1,2、Akihiko Shinya^1,2、Masaya Notomi^1,2 (1.NTT NPC、2.NTT BRL)

キーワード：nanowire, photonic crystal

Nanowire (NW) lasers for on-chip light sources are highly desirable, as their compact nature allows for a wide range of photonic applications. However, subwavelength semiconductor NWs prove to be difficult as they cannot support photonic Fabry-Pérot resonances and typically have poor light confinement not suitable for room-temperature cw lasing. One possibility to improve the properties of subwavelength NWs, is to embed it in a Si photonic crystal (PhC) grooved waveguide to achieve both a high Q and large light confinement (Γ_nw). We previously had demonstrated cw NW (100 nm) lasers on a Si PhC platform under cryogenic conditions using cw photo pumping. However, due to inhomogeneous NW structures and fabrication errors, only a Q of 9200 was measured. Accordingly, our target is to optimize a nanocavity mode concentrated in the NW, capable of achieving cw lasing by current injection with accountancies for variable NW lengths and diameters. Our design uses a modified L3 type cavity with a single row defect channel. The inner 3 holes on both sides of the L3 cavity along the channel are scaled and shifted proportional to the lattice constant to increase Q. PhC fabrication aside, we also determined the effect varying radii (d_nw) (100 nm – 200 nm) and lengths (L_nw) of the NWs have on Q and Γ_nw still within subwavelength dimensions. The last criteria we explored was the addition of gold composite current injection contact pads and what effect it would have on our device. Typically, gold has a large absorption coefficient, 10,000 times larger than InP, and is capable of reducing Q significantly, relative to the separation distance, width, and thickness of the pads around the cavity. To this end, we extensively explored the various dimensional and intrinsic parameters that directly affect the performance of our purposed device, using Q and Γ_nw as metrics. To clarify, Γ_nw is the field energy confined in the NW over the total system energy. With a highly optimized structure, including contact pads, we can achieve a maximum Q of ~ 4.0 and Γ of ~ 20%. Even with smaller diameter NWs, Γ_nw of ~10% can be obtained, indicating our design allows for better tolerance in NW dimensional imperfections.