We propose a freestanding GaN-based integrated photonics chip with ultra-micro LED and straight waveguide for visible light communication on GaN-on-silicon platform realized by double-side process. The ultra-micro LED and waveguide is prepared by dry etching for GaN, electron beam evaporation for metal electrode, plasma enhanced chemical vapor deposition (PECVD) and wet etching for SiO2. The silicon substrate under chip is totally removed by deep inductive coupled plasma (ICP) etching to realize the freestanding membrane. The ultra-micro LED emits visible light signal in blue range. The visible light signal is coupled into straight waveguide connected to ultra-micro LED, and transmitted to tip of waveguide end. The communication performance of chip is significantly influenced by the active area of LED. Ultra-micro LED could well confine the visible light signal in waveguide, and achieve greater modulation bandwidth. The technical difficulty of chip with ultra-micro LED is to make p-electrode pad on active area with ultramicro size. We realize p-electrode pad with relatively large size on ultra-micro LED with SiO2 isolation layer. Light transmission performance of chip verse current is quantitatively analyzed by measuring intensity of visible light transmitted to waveguide tip. Most of the light emitted from ultra-micro LED is well confined in straight waveguide. The light intensity of waveguide tip is strongly modulated by the geometric parameters of straight waveguide. Freespace visible light communication (VLC) test with 120Mbps random binary sequence is carried out to achieve high speed data transmission. This study provides a potential approach for GaN-based integrated photonics chip as ultramicro light source and passive optical device in visible range.
The multifunctional technology is essential for the Internet of things in which a single device can have multifunctionalities for the development of monolithic multicomponent system. GaN photonics provides a great potential to integrate photonic and electronic circuits on a single chip for modern computing system architecture. When appropriately biased, multiple quantum well (MQW) diode intrinsically exhibits the simultaneous emission-detection phenomenon because there is a spectral overlap between the electroluminescence spectra and photocurrent responsivity spectra. We come up with the Wang effect to make a fundamental interpretation of the intriguing phenomenon, and experimentally demonstrate full-duplex audio communication using the dual-functioning MQW-diode, which can simultaneously transmit and receive information using visible light.
We demonstrate a wafer-level process for achieving monolithic photonic integration of a light-emitting diode (LED) with a waveguide and photodiode on a GaN-on-silicon platform. Both silicon removal and back-side thinning are conducted to achieve a suspended device architecture. A highly confined waveguide that utilizes the large index contrast between GaN and air is used for the connection between the LED and the photodiode. The suspended waveguide is considered as an in-plane escape cone of the LED, and the photodiode is located at the other end of the waveguide. The photons emitted from the LED are transported to the photodiode through the suspended waveguide parallel to the LED surface, leading to in-plane data transport using visible light. This proof-of-concept monolithic integration paves the way towards in-plane visible light communication as well as photonic computation on a single chip.
Recently, visible light positioning has gradually become a research hotspot in indoor environments. Based on a single transmitter and a single tilted optical receiver, a three-dimensional (3-D) indoor visible light positioning system is proposed. The tilted optical receiver is installed on a rotatable and retractable platform. The 3-D space is divided many two-dimensional (2-D) planes by lifting the platform of the optical receiver. In each 2-D plane, various azimuth angles can be obtained by rotating the receiver platform, which offers a feasible way to perform multiple measurements with different azimuth angles to achieve the angle gain. According to the difference of the angle gain, a 3-D positioning algorithm is proposed. Experimental results show that the proposed positioning algorithm can provide good positioning accuracy.
We present a method for distinguishing human face from high-emulation mask, which is increasingly
used by criminals for activities such as stealing card numbers and passwords on ATM. Traditional
facial recognition technique is difficult to detect such camouflaged criminals. In this paper, we use the
high-resolution hyperspectral video capture system to detect high-emulation mask. A RGB camera is
used for traditional facial recognition. A prism and a gray scale camera are used to capture spectral
information of the observed face. Experiments show that mask made of silica gel has different spectral
reflectance compared with the human skin. As multispectral image offers additional spectral
information about physical characteristics, high-emulation mask can be easily recognized.
We present a new hybrid camera system based on spatial light modulator (SLM) to capture texture-adaptive
high-resolution hyperspectral video. The hybrid camera system records a hyperspectral video with low spatial resolution
using a gray camera and a high-spatial resolution video using a RGB camera. The hyperspectral video is subsampled by
the SLM. The subsampled points can be adaptively selected according to the texture characteristic of the scene by
combining with digital imaging analysis and computational processing. In this paper, we propose an adaptive sampling
method utilizing texture segmentation and wavelet transform (WT). We also demonstrate the effectiveness of the
sampled pattern on the SLM with the proposed method.
Homoepitaxial grown InGaN/GaN p-i-n junction was deposited on GaN/Si template with AlN/GaN supperlattice as interlayer by molecular beam epitaxy. Different surface microstructure of the p-GaN was affected by the amount of Mg flux. Light-emitting diode was fabricated from the p-i-n junction. The crystal properties of InGaN/GaN p-i-n junction and the related light-emitting diode properties were investigated.