Qingquan Liu

We present a new strategy to produce high performance flexible transparent electrode based on broadband induced transmission. The mechanism allows metal layer to achieve broadband transparency while maintaining high conductivity simultaneously, overcoming the drawback of low infrared transmittance in conventional transparent conductors. To demonstrate this concept, a simple tri-layer structure has been fabricated to produce a short-wave infrared (SWIR) transparent electrode with high transmittance and conductivity simultaneously. The experimental results show that the SWIR transparent electrode has average transmittance of 80% and sheet resistance as low as 8.5 Ω/sq, with huge advantage in terms of transmittance bandwidth. The typical infrared imaging result shows that the Michelson contrast is 1.6 times better than that of ITO. Such an infrared transparent electrode can be produced on large scale by using mature technology. It paves a way for the design of high performance infrared transparent electrode and has significant application potentials for infrared optoelectronics devices, including near infrared solar cells, flexible smart display screen and micro spectrometers.

Metalenses play an important role in optoelectronic integrated devices, given their advantages in miniaturization and integration. Due to its high aspect ratio subwavelength structure, fabricating metalenses requires a high-level dry etching technology. Consequently, structure deformation of the metalens will exist if the etching process of the material is not mature enough, which will impair the metalens’ performance. In this paper, a polarization-independent InP dielectric metalens is designed to focus the incident light from air into the substrate, which is used for monolithically integrating with the InGaAs/InP photodetector in the future. Subsequently, with the simulation method, we investigated the impact of the structure deformation on the metalens’ performance, which was found in our InP dry etching process development. We have found that the sidewall slope and aspect ratio-dependent etching effect greatly impaired the focusing efficiency because of the phase modulation deviation. To solve this problem, we proposed a manufacturing-tolerant design method, which effectively improved the performance of the device with structural deformation. Our work is instructive for developing metalenses and can accelerate their integration application.

There is a problem of insufficient reference tracking accuracy in servo system driven by permanent magnet synchronous motor (PMSM), which limits its application. This paper aims to propose a modified error-driven preset-input least mean square adaptive filter (EPLMS-AF) to improve the tracking accuracy. The reference tracking error is used to drive the update of adaptive weights in EPLMS-AF. The designed preset-inputs makes the reference tracking error converge to zero according to the form of reference. On the premise of choosing an appropriate iteration size to ensure the stability of the filter, the tracking error is able to reduce to zero along the gradient direction. At last, numerical simulations are provided to illustrate the high efficiency and wide applicability of the proposed method.

Low-threshold single-mode laser in CsPbBr₃ microdiscs grown between two distributed Bragg reflectors (DBRs) is realized at room temperature. The CsPbBr₃ microdiscs are directly synthesized on the surface of prepared first-half DBRs microcavity by a chemical vapor deposition method. This scheme avoids possible surface damage or contamination caused by the traditional transfer of sample into the DBRs. The single-mode laser with low threshold (∼1.3 μJ/cm²) was obtained in the CsPbBr₃ microdiscs sandwiched in DBRs and measured by using the micro-photoluminescence spectroscopy. The length of the resonant cavity is short enough to support a large free spectral range, which ensures only one mode in the bandwidth of the optical gain. Moreover, by modulating the thickness of the CsPbBr₃ microdiscs, the wavelength of single-mode laser emission can be broadly tuned from 529.6 to 544.1 nm. This work provides a method of fabricating single-mode laser in DBRs, which may have potential applications in on-chip integration of optoelectronic devices and signal processing.

Fluorescence imaging is very useful for skin cancer lesions detection because of its properties of noninvasion and fast imaging. However, conventional fluorescence imaging devices’ excitation light source and camera are usually separated, which will cause problems such as complicated structure, large volume, and poor illumination homogeneity. In this paper, we introduce a miniature portable fluorescence imaging device to diagnose skin cancer. A coaxial design has been introduced to combine the exciting light source and fluorescence receiver as an integral part, which significantly reduces the size of the device and ensures illumination homogeneity. The volume of the device is less than [ ][ ]cm³ with weight of 150[ ]g, and the total power (including the excitation lamp) is only 1.5 W. It is used to detect the squamous cell carcinoma mice for demonstration. The results show that the location of the cancer lesions can be easily distinguished from the images captured by the device. It can be efficiently used to detect early skin tumors with noninvasion. It also has prospects to be integrated with other diagnostic methods such as ultrasound probe, for multiple diagnose of skin tumors thanks to its miniature size.

In the nearest decades, the rapidly increasing demand of wireless connectivity has resulted in the ubiquitous deployment of wireless systems as well as heavily congested wireless spectrum. Owing to the various inherent advantages, such as spectral and bandwidth relief, no healthy concern, high security, low cost, and low interference with Radio Frequency (RF) waves, visible light communication (VLC) has been an emerging optical wireless data transmission approach that can act as a good complement to and substitute for Radio Frequency. How to achieve a high-speed data transmission is a key problem to be solved in the VLC system. This review mainly focuses on the enabling technologies for high-speed VLC systems, including novel transmitter architectures, blue filters and advanced modulation, and equalization technologies. And the inherent advantages, potential applications, and some issues of VLC that need further study are presented as well. Finally, a comprehensive survey on the recent developments and the key contributions by research groups involved in the field of high-speed VLC is provided.