[15p-B4-9~20] 3.11 フォトニック構造・現象

▲ [15p-B4-19] Fabrication and Optical Properties of ZnO-nanowire-induced nanocavities in grooved SiN photonic crystals

〇Sylvain SERGENT^1,2、Masato Takiguchi^1,2、Atsushi Yokoo^1,2、Hideaki Taniyama^1,2、Akihiko Shinya^1,2、Eichi Kuramochi^1,2、Tai Tsuchizawa^1,3、Tetsuya Akasaka²、Masaya Notomi^1,2 (1.NTT NPC、2.NTT BRL、3.NTT DTL)

キーワード：Photonic crystal, Nanowire, UV photonics

Semiconductor nanowires positioned in grooved Si photonic crystals (PhCs) have recently been shown to be a promising and versatile platform to achieve high-Q nanocavities in the infra-red range [1]. We here show that this approach can be extended to shorter wavelengths, using grooved SiN PhCs and ZnO single nanowires (NW) (Fig 1 (a)), a configuration that would be of interest for the realization of near-UV nanolasing and more. According to three dimensional finite-difference time-domain (3D-FDTD) calculations, such NW-induced cavities with a 3-μm-long and 90-nm wide NW can present a fundamental mode with a quality factor Q = 1.8x10⁴ and a mode volume V = 5.52(λ/n)³ in the near-UV range (Fig 1 (b)). We implement this design by first fabricating free-standing two-dimensional (2D) PhC line-defect waveguides in a 100-nm-thick SiN slab obtained by plasma-enhanced chemical vapor deposition on a silicon substrate. A 90-nm-wide groove is then defined in the waveguide and ZnO NWs are dispersed on the surface of the patterned SiN. Individual NWs are finally positioned inside the grooved PhC by atomic force microscope nanomanipulation (Fig 1 (c)). As predicted by 3D-FDTD, room-temperature μPL of bare ZnO NWs do not present any spectral feature indicating the presence of photonic Fabry-Pérot modes, whereas NWs positioned in grooved PhCs exhibit NW-induced nanocavity resonances in the near-UV range (Fig 1 (d)). We show that the optical properties of such resonant modes are in fair agreement with 3D-FDTD calculations and we report on quality factors as high as Q = 1.4x10³ at λ = 397 nm, which is a promising first step toward the use of ZnO-NW-induced nanocavities for the realization of nanolasers.
This work was supported by JSPS KAKENHI Grant Number 15H05735.
[1] M. D. Birowosuto et al., Nature Materials 13, 279 (2014).