Chiral Isolator, Plasmonic Nanolaser, and Hybrid Sensor Based on One-dimensional Photonic Structure

• Main Authors: Cheng, Pi-Ju, 鄭璧如
• Other Authors: Tien, Chung-Hao
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/qrv5u3

博士 === 國立交通大學 === 光電工程研究所 === 104 === The photon manipulation and optical control are essential for photonic integrated circuits. In this dissertation, we look into isolators, nanolasers, and sensors which are made up of one-dimensional photonic structures and may play advanced roles therein. We begin by theoretically analyzing an optical isolator based on strongly-guided chiral photonic-crystal waveguides. Without breaking the reciprocity, the propagating modes in this chiral waveguide are not backscattering-immune even though they are insensitive to many types of scatters. We use the first-order Born approximation and coupled-mode theory to unfold the rules of strong backscattering. The criteria required to avoid the backscattering in this chiral structure will be worked out. On the generation and sensing of photons, semiconductor-based photonic devices tend to follow the path toward miniaturization. The smaller devices could be more energy-efficient or material-saving. By mixing photons with surface plasmons into polaritons, metals provide a way to overcome the diffraction limit. To reach coherent nanoscale photon sources, we analytically examine plasmonic gap-mode nanocavities consisting of metallic nanowires (NWRs) at telecommunication wavelengths. We investigate the covering effect of thick cladding on the plasmonic cavity. Within a certain index range of the cladding, the fundamental hybrid plasmonic mode is the most promising lasing mode. However, in the presence of high-index cladding materials, the lasing action of the first-order gap mode is more favorable. In both cases, the mirror loss is the main challenge to lasing. With silver coatings at two end facets, the reflectivity is substantially enhanced, and a decent quality (Q) factor for the lasing mode is achievable. On the sensing side, the combination of photonic crystals (PhCs) and plasmonics could bring about the manipulation of photons at the extremely small scale. We accordingly proposed a hybrid plasmonic-PhC nanocavity composed of silicon NWRs near the metal surface. Periodic corrugations are imposed on the NWR. Such hybrid periodic structures can support a complete one-dimensional bandgap. A defect structure is further introduced into the NWR PhC to confine the optical energy in the nanoscale. The nanocavity has a high ratio between the Q factor and modal volume and can boost the light-matter interaction. The high sensitivity and Q factor are also present as immersed in aqueous solutions. This structure could function as label-free biosensors in lab-on-a-chip devices based on the bottom-up technology.