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282 results on '"Jin, Yuhao"'

2. Impact of cavity geometry on microlaser dynamics

Author

Kim, Kyungduk, Bittner, Stefan, Jin, Yuhao, Zeng, Yongquan, Wang, Qi Jie, and Cao, Hui

Subjects
Physics - Optics
Abstract

We experimentally investigate spatio-temporal lasing dynamics in semiconductor microcavities with various geometries, featuring integrable or chaotic ray dynamics. The classical ray dynamics directly impacts the lasing dynamics, which is primarily determined by the local directionality of long-lived ray trajectories. The directionality of optical propagation dictates the characteristic length scales of intensity variations, which play a pivotal role in nonlinear light-matter interactions. While wavelength-scale intensity variations tend to stabilize lasing dynamics, modulation on much longer scales causes spatial filamentation and irregular pulsation. Our results will pave the way to control the lasing dynamics by engineering the cavity geometry and ray dynamical properties., Comment: The first two authors have equal contribution. 17 pages, 13 figures

Published
2023
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3. Spatio-temporal lasing dynamics in a Lima\c{c}on-shaped microcavity

Author

Kim, Kyungduk, Bittner, Stefan, Jin, Yuhao, Zeng, Yongquan, Wang, Qi Jie, and Cao, Hui

Subjects
Physics - Optics
Abstract

Lima\c{c}on-shaped microdisk lasers are promising on-chip light sources with low lasing threshold and unidirectional output. We conduct an experimental study on the lasing dynamics of Lima\c{c}on-shaped semiconductor microcavities. The edge emission exhibits intensity fluctuations over a wide range of spatial and temporal scales. They result from multiple dynamic processes with different origins and occurring on different spatiotemporal scales. The dominant process is an alternate oscillation between two output beams with a period as short as a few nanoseconds., Comment: 7 pages, 6 figures

Published
2022
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7. Sensitive control of broad-area semiconductor lasers by cavity shape

Author

Kim, Kyungduk, Bittner, Stefan, Jin, Yuhao, Zeng, Yongquan, Guazzotti, Stefano, Hess, Ortwin, Wang, Qi Jie, and Cao, Hui

Subjects
Physics - Optics
Abstract

The ray dynamics of optical cavities exhibits bifurcation points: special geometries at which ray trajectories switch abruptly between stable and unstable. A prominent example is the Fabry-Perot cavity with two planar mirrors, which is widely employed for broad-area semiconductor lasers. Such cavities support lasing in a relatively small number of transverse modes, and the laser is highly susceptible to filamentation and irregular pulsations. Here we demonstrate experimentally that a slight deviation from this bifurcation point (planar cavity) dramatically changes the laser performance. In a near-planar cavity with two concave mirrors, the number of transverse lasing modes increases drastically. While the spatial coherence of the laser emission is reduced, the divergence angle of the output beam remains relatively narrow. Moreover, the spatio-temporal lasing dynamics becomes significantly more stable compared to that in a Fabry-Perot cavity. Our near-planar broad-area semiconductor laser has higher brightness, better directionality and hence allows shorter integration times than an incandescent lamp while featuring sufficiently low speckle contrast at the same time, making it a vastly superior light source for speckle-free imaging. Furthermore, our method of controlling spatio-temporal dynamics with extreme sensitivity near a bifurcation point may be applied to other types of high-power lasers and nonlinear dynamic systems., Comment: 17 pages, 11 figures

Published
2022
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32. Single‐Mode Electrically Pumped Terahertz Laser in an Ultracompact Cavity via Merging Bound States in the Continuum (Laser Photonics Rev. 17(11)/2023)

Author

Cui, Jieyuan, primary, Chua, Yunda, additional, Han, Song, additional, Wang, Chongwu, additional, Jin, Yuhao, additional, Li, Jinghao, additional, Zeng, Yongquan, additional, Wang, Qian, additional, Ye, Ming, additional, Chen, Wenduo, additional, Zhu, Song, additional, Sun, Fangyuan, additional, Li, Lianhe, additional, Davies, Alexander Giles, additional, Linfield, Edmund Harold, additional, Tan, Chuan Seng, additional, and Wang, Qi Jie, additional

Published
2023
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36. Electrically pumped topological laser with valley edge modes

Author

Zeng, Yongquan, Chattopadhyay, Udvas, Zhu, Bofeng, Qiang, Bo, Li, Jinghao, Jin, Yuhao, Li, Lianhe, Davies, Alexander Giles, Linfield, Edmund Harold, Zhang, Baile, Chong, Yidong, and Wang, Qi Jie

Subjects
Crystals -- Usage, Lasers -- Equipment and supplies, Laser, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Quantum cascade lasers are compact, electrically pumped light sources in the technologically important mid-infrared and terahertz region of the electromagnetic spectrum.sup.1,2. Recently, the concept of topology.sup.3 has been expanded from condensed matter physics into photonics.sup.4, giving rise to a new type of lasing.sup.5-8 using topologically protected photonic modes that can efficiently bypass corners and defects.sup.4. Previous demonstrations of topological lasers have required an external laser source for optical pumping and have operated in the conventional optical frequency regime.sup.5-8. Here we demonstrate an electrically pumped terahertz quantum cascade laser based on topologically protected valley edge states.sup.9-11. Unlike topological lasers that rely on large-scale features to impart topological protection, our compact design makes use of the valley degree of freedom in photonic crystals.sup.10,11, analogous to two-dimensional gapped valleytronic materials.sup.12. Lasing with regularly spaced emission peaks occurs in a sharp-cornered triangular cavity, even if perturbations are introduced into the underlying structure, owing to the existence of topologically protected valley edge states that circulate around the cavity without experiencing localization. We probe the properties of the topological lasing modes by adding different outcouplers to the topological cavity. The laser based on valley edge states may open routes to the practical use of topological protection in electrically driven laser sources. A topological laser based on the valley degree of freedom in a compact photonic crystal can be pumped electrically, bringing topological physics concepts closer to real-life applications., Author(s): Yongquan Zeng [sup.1] , Udvas Chattopadhyay [sup.2] , Bofeng Zhu [sup.2] , Bo Qiang [sup.1] [sup.2] , Jinghao Li [sup.1] , Yuhao Jin [sup.1] , Lianhe Li [sup.3] , [...]

Published
2020
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47. CR-DINO: A Novel Camera-Radar Fusion 2-D Object Detection Model Based on Transformer

Author

Jin, Yuhao, Zhu, Xiaohui, Yue, Yong, Lim, Eng Gee, and Wang, Wei

Abstract

Due to millimeter-wave (MMW) radar’s ability to directly acquire spatial positions and velocity information of objects, as well as its robust performance in adverse weather conditions, it has been widely employed in autonomous driving. However, radar lacks specific semantic information. To address this limitation, we take the complementary strengths of camera and radar by feature-level fusion and propose a fully transformer-based model for object detection in autonomous driving. Specifically, we introduce a novel radar representation method and propose two camera-radar fusion architectures based on Swin transformer. We name our proposed model as camera-radar based DETR with improved denoising anchor boxes (CR-DINO) and conduct training and testing on the nuScenes dataset. We conducted several ablation experiments, and the best result we obtained was an mAP of 38.0%, surpassing other state-of-the-art (SOTA) camera-radar fusion object detection models.

Published
2024
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