Browsing by Author "Yuan, Qingchen"

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Low‐Power Continuous‐Wave Second Harmonic Generation in Semiconductor Nanowires
(2018-10) Yuan, Qingchen; Fang, Liang; Yang, He; Gan, Xuetao; Khayrudinov, Vladislav; Lipsanen, Harri; Sun, Zhipei; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Semiconductor nanowires (NWs) are promising for realizing various on‐chip nonlinear optical devices, due to their nanoscale lateral confinement and strong light–matter interaction. However, high‐intensity pulsed pump lasers are typically needed to exploit their optical nonlinearity because light couples poorly with nanometric‐size wires. Here, microwatts continuous‐wave light pumped second harmonic generation (SHG) in AlGaAs NWs is demonstrated by integrating them with silicon planar photonic crystal cavities. Light–NW coupling is enhanced effectively by the extremely localized cavity mode at the subwavelength scale. Strong SHG is obtained even with a continuous‐wave laser excitation with a pump power down to urn:x-wiley:18638880:media:lpor201800126:lpor201800126-math-0001W, and the cavity‐enhancement factor is estimated around 150. Additionally, in the integrated device, the NW's SHG is more than two orders of magnitude stronger than third harmonic generations in the silicon slab, though the NW only couples with less than 1% of the cavity mode. This significantly reduced power requirement of NW's nonlinear frequency conversion would promote NW‐based building blocks for nonlinear optics, especially in chip‐integrated coherent light sources, entangled photon pairs and signal processing devices.
Mode couplings of a semiconductor nanowire scanning across a photonic crystal nanocavity
(2019-06-10) Yuan, Qingchen; Fang, Liang; Zhao, Qiang; Wang, Yadong; Mao, Bo; Khayrudinov, Vladislav; Lipsanen, Harri; Sun, Zhipei; Zhao, Jianlin; Gan, Xuetao
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The position-dependent mode couplings between a semiconductor nanowire (NW) and a planar photonic crystal (PPC) nanocavity are studied. By scanning anNWacross a PPC nanocavity along the hexagonal lattice's Γ -M and M - K directions, the variations of resonant wavelengths, quality factors, and mode volumes in both fundamental and second-order resonant modes are calculated, implying optimal configurations for strong mode-NW couplings and light-NW interactions. For the fundamental (second-order) resonant mode, scanning anNWalong theM- K (Γ - M) direction is preferred, which supports stronger light-NW interactions with larger NW-position tolerances and higher quality factors simultaneously. The simulation results are confirmed experimentally with good agreements.
Nanowire-assisted microcavity in a photonic crystal waveguide and the enabled high-efficiency optical frequency conversions
(2020-10-22) Gu, Linpeng; Fang, Liang; Yuan, Qingchen; Gan, Xuetao; Hao, Yang; Zhang, Xutao; Li, Juntao; Fang, Hanlin; Khayrudinov, Vladislav; Lipsanen, Harri; Sun, Zhipei; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
We report an indium phosphide nanowire (NW)-induced cavity in a silicon planar photonic crystal (PPC) waveguide to improve the light–NW coupling. The integration of NW shifts the transmission band of the PPC waveguide into the mode gap of the bare waveguide, which gives rise to a microcavity located on the NW section. Resonant modes with 푄 factors exceeding 103 are obtained. Leveraging on the high density of the electric field in the microcavity, the light–NW interaction is enhanced strongly for efficient nonlinear frequency conversion. Second-harmonic generation and sum-frequency generation in the NW are realized with a continuous-wave pump laser in a power level of tens of microwatts, showing a cavity-enhancement factor of 112. The hybrid integration structure of NW-PPC waveguide and the self-formed microcavity not only opens a simple strategy to effectively enhance light–NW interactions, but also provides a compact platform to construct NW-based on-chip active devices.