Compact pupil-expansion AR-HUD based on surface-relief grating.

Augmented reality head-up display (AR-HUD) using diffractive waveguide is a challenging research field. It can drastically reduce the system volume compared with AR-HUD based on freeform mirror. However, one of the remaining challenges that affects the performance of the diffractive waveguide is to expand the eye-box while maintaining the illuminance uniformity. In this paper, a one-dimensional pupil expansion diffractive optical waveguide system for AR-HUD is presented. The optimization of grating parameters is based on scalar diffraction theory and rigorous coupled wave analysis (RCWA). Then, the illuminance uniformity is optimized through non-sequential ray tracing. We simulate and construct a waveguide-based AR-HUD. The presented AR-HUD realized an exit pupil size of 80 mm × 15 mm and a field of view of 10° × 5° at the wavelength of 532 nm.

A Review on Micro-LED Display Integrating Metasurface Structures.

Micro-LED display technology has been considered a promising candidate for near-eye display applications owing to its superior performance, such as having high brightness, high resolution, and high contrast. However, the realization of polarized and high-efficiency light extraction from Micro-LED arrays is still a significant problem to be addressed. Recently, by exploiting the capability of metasurfaces in wavefront modulation, researchers have achieved many excellent results by integrating metasurface structures with Micro-LEDs, including improving the light extraction efficiency, controlling the emission angle to achieve directional emission, and obtaining polarized Micro-LEDs. In this paper, recent progressions on Micro-LEDs integrated with metasurface structures are reviewed in the above three aspects, and the similar applications of metasurface structures in organic LEDs, quantum dot LEDs, and perovskite LEDs are also summarized.

Trap Characterization Techniques for GaN-Based HEMTs: A Critical Review.

Gallium nitride (GaN) high-electron-mobility transistors (HEMTs) have been considered promising candidates for power devices due to their superior advantages of high current density, high breakdown voltage, high power density, and high-frequency operations. However, the development of GaN HEMTs has been constrained by stability and reliability issues related to traps. In this article, the locations and energy levels of traps in GaN HEMTs are summarized. Moreover, the characterization techniques for bulk traps and interface traps, whose characteristics and scopes are included as well, are reviewed and highlighted. Finally, the challenges in trap characterization techniques for GaN-based HEMTs are discussed to provide insights into the reliability assessment of GaN-based HEMTs.

Are women in China sexist toward other women? A study of Chinese college students.

This study assessed the extent to which social sexism affects Chinese women's perception and evaluation of other women's performance. A sample of 100 college women was selected in a top university in Beijing, China, and was asked to read six scholastic essays and then evaluate the quality of the essays and competence of the authors. Male and female names were randomly assigned as authors of the essays, and the respondents were blind to the arrangement. Results showed that the essays assumed to be written by male authors did not receive higher scores than those assumed to be written by female authors on quality or competence items. Sexism is not marked among these highly educated young women.