Qi Zhang

Institute of Optics and Electronics, Chinese Academy of Sciences

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Lijia Zhang

Northeast Forestry University

Qinghua Tian

Beijing University of Posts and Telecommunications

Feng Tian

Okayama University

Xiangjun Xin

Beijing University of Posts and Telecommunications

Yongjun Wang

Beihang University

Mingbo Pu

Chinese Academy of Sciences

Xiangang Luo

Chinese Academy of Sciences

Lan Rao

Beijing University of Posts and Telecommunications

Yinghui Guo

Institute of Optics and Electronics, Chinese Academy of Sciences

Fei Zhang

Chinese Academy of Sciences

Cooperative Institutions

Chinese Academy of Sciences

University of Chinese Academy of Sciences

Institute of Optics and Electronics, Chinese Academy of Sciences

Beijing University of Posts and Telecommunications

Suzhou Institute of Nano-tech and Nano-bionics

University of Science and Technology of China

Sun Yat-sen University

State Key Laboratory of Information Photonics and Optical Communications

State Key Laboratory on Integrated Optoelectronics

Huazhong University of Science and Technology

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Realization of GaN-based gain-guided blue laser diodes by helium ion implantation

Semiconductor Science and Technology (2019)

Qi Zhang Shuming Zhang Feng Zhang Junjie Hu Meixin Feng

The fabrication process and characteristics of gallium nitride (GaN) based gain-guided blue laser diodes (LDs) are studied, in which an ion implantation process is adopted to confine carrier injection into the active region. The implantation of helium ions with an energy of 85 keV, an angle of 0°, and a dosage of 4.7 × 1014 cm−2 is conducted in the experiment. The specific contact resistivity of p-type ohmic contact of implanted sample is determined to be 2.2 × 10–4 Ω cm2, which is comparable with the un-implanted sample. Then, both ion-implanted gain-guided and ridge waveguide LDs are fabricated at the same time. Similar threshold current density and slope efficiency are obtained, while the operation voltage of ion-implanted gain-guided LDs is 0.2 V lower than the ridge waveguide LDs at 0.56 kA cm−2. The ridge waveguide LDs show multi-mode operation after lasing. However, for ion-implanted gain-guided LDs, the far-field pattern indicates a single lateral mode operation up to twice of the threshold current, and the peak optical output power of blue single mode LDs at 450 nm exceeds 200 mW under pulsed condition.

Realization (probability)

10.1088/1361-6641/ab429c

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Citations (2)

Vectorial Digitelligent Optics for High-Resolution Non-Line-of-Sight Imaging

Engineering (2024)

Yinghui Guo Yunsong Lei Mingbo Pu Fei Zhang Qi Zhang

Non-line-of-sight propagation

Sight

Line-of-sight

Line (geometry)

10.1016/j.eng.2024.11.013

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離散ウェーブレット変換に基づく直接変調された複数フォーマット光OFDMシステム【Powered by NICT】

IEEE Conference Proceedings (2016)

Yan Zhou Бо Лю Lijia Zhang Xiangjun Xin Qi Zhang

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二重円反復法に基づく光パルス位置変調【Powered by NICT】

IEEE Conference Proceedings (2016)

Wei Xia Bo Liu Lijia Zhang Xiangjun Xin Qi Zhang

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Analysis on abnormal forward conduction properties in GaN based JBS diode by TCAD simulation

Qi Zhang Qianshu Wu Yapeng Wang Qiuling Qiu Zhenxing Liu

Abnormal phenomenon that on-resistance of JBS diode increases with forward bias has been studied in this work. It is found that the forward bias is mainly applied to the p-type Schottky junction, resulting in a slower electric potential increasing rate of p-GaN than n-type channel between adjacent p-grid. Therefore, the lateral PN junction at channel is reversely biased and the effective conduction area of JBS diode reduces, which results in the increase of on-resistance. JBS diodes with different Schottky barrier height at p-type Schottky contact are also simulated to verify our analysis. The decrease of barrier height at p-type Schottky junction results in that the anode voltage is mainly applied to the PN junction, which can shorten the lateral depletion region and decrease the on-resistance of JBS diode. The simulation results in this paper are useful for providing reference advice for following experiments.

Equivalent series resistance

Metal–semiconductor junction

10.1109/sslchinaifws57942.2023.10070928

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Vectorial‐Optics‐Enabled Multi‐View Non‐Line‐Of‐Sight Imaging with High Signal‐To‐Noise Ratio

Laser & Photonics Review (2024)

Zewei Wang Xiaoyin Li Mingbo Pu Lianwei Chen Fei Zhang

Abstract Non‐line‐of‐sight (NLOS) imaging enables the reconstruction of targets beyond the direct line of sight, which has extensive applications across various fields. However, it remains unclear how and to what extent the vectorial nature of light, which plays a critical role in optical imaging and object recognition, can enhance the imaging performance of active NLOS imaging. Here, this work proposes a method that utilizes vector optical fields (VOFs) with arbitrarily designed polarization distributions to realize NLOS imaging in challenging conditions with low signal‐to‐noise ratio (SNR). A generalized VOF reflection model is established at the relay surface for active NLOS imaging to determine the optimal illumination angle and polarization as well as the received polarization. Based on this model, the feasibility of multi‐view NLOS imaging is demonstrated with enhanced SNR of echo signals under proper VOF modulation, surpassing the limitations of conventional single‐view NLOS imaging. Simulations and experiments validate the superior performance of the proposed approach to realize accurate reconstruction and recognition of hidden objects.

SIGNAL (programming language)

Line-of-sight

Line (geometry)

Non-line-of-sight propagation

Sight

10.1002/lpor.202300909

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Citations (8)

High-resolution non-line-of-sight imaging based on liquid crystal planar optical elements

Nanophotonics (2024)

Zhi-Bin Zhao Qi Zhang Xiaoyin Li Yinghui Guo Mingbo Pu

Non-line-of-sight (NLOS) imaging aims at recovering hidden objects located beyond the traditional line of sight, with potential applications in areas such as security monitoring, search and rescue, and autonomous driving. Conventionally, NLOS imaging requires raster scanning of laser pulses and collecting the reflected photons from a relay wall. High-time-resolution detectors obtain the flight time of photons undergoing multiple scattering for image reconstruction. Expanding the scanning area while maintaining the sampling rate is an effective method to enhance the resolution of NLOS imaging, where an angle magnification system is commonly adopted. Compared to traditional optical components, planar optical elements such as liquid crystal, offer the advantages of high efficiency, lightweight, low cost, and ease of processing. By introducing liquid crystal with angle magnification capabilities into the NLOS imaging system, we successfully designed a large field-of-view high-resolution system for a wide scanning area and high-quality image reconstruction. Furthermore, in order to reduce the long data acquisition time, a sparse scanning method capitalizing on the correlation between measurement data to reduce the number of sampling points is thus proposed. Both the simulation and experiment results demonstrate a >20 % reduction in data acquisition time while maintaining the exact resolution.

Nanomaterials

Line (geometry)

Sight

10.1515/nanoph-2023-0655

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Shortening Focal Length of 100‐mm Aperture Flat Lens Based on Improved Sagnac Interferometer and Bifacial Liquid Crystal

Advanced Optical Materials (2023)

Yifeng Wen Qi Zhang Qiong He Feifei Zhang Lingxing Xiong

Abstract Conventional lens technologies face great challenges in applications requiring large apertures and small f‐numbers, while a liquid crystal (LC) lens based on geometric phase is a potential solution. However, the challenge of manufacturing a large size LC flat lens with high efficiency and high phase gradient still remains. Here, an improved interferometric exposure system is proposed to acquire a large‐size vectorial optical field for photo‐alignment. Bifacial LC layers are applied to reduce the focal length while maintaining a large aperture, high diffraction efficiency, and light weight. LC layers are deposited on both sides of the substrate with the same vector system. Finally, a bifacial LC flat lens with a 10 cm diameter and 88.37% diffraction efficiency is fabricated by using optical elements smaller than 2 in., while the effective focal length is reduced from 91.5 cm to 46 cm comparing to the single side LC lens. This work demonstrates the great advantages of LC‐based flat lenses for flat optical systems with large aperture.

Aperture (computer memory)

Diffraction efficiency

10.1002/adom.202300127

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Citations (12)

高非線形ファイバにおける並列相互位相変調を用いた位相変調光信号のための偏光モード分散モニタリング【Powered by NICT】

IEEE Conference Proceedings (2016)

Junde Chang Bo Liu Lijia Zhang Xiangjun Xin Qi Zhang

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A power-constrained contrast enhancement algorithm for AMOLED display using histogram segmentation

Wenhua Qiang Qi Zhang Wei Miao Guohong Li Hui Wang

A power-constrained contrast enhancement algorithm is proposed for high contrast low power active-matrix organic light-emitting diode (AMOLED) display. The contrast enhancement and power constraint are implemented respectively for each histogram segment. The proposed algorithm is simple in order to be implemented into the hardware. Simulation results demonstrate that the proposed algorithm can reduce the power consumption significantly with image contrast conservation. The local detail of the processed image is clearer than the original one. The proposed algorithm is also implemented to a 2.8-inch AMOLED display to confirm its effectiveness.

AMOLED

10.1109/asicon.2013.6812072

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