A passive‐matrix monolithic full‐color InGaN light emitting diode (LED) microdisplay with 40 × 40 full‐color pixels is demonstrated. Each full‐color pixel consists of red, green, and blue (RGB) subpixels that have a pitch size of 40 μm × 120 μm. The full‐color microdisplay is monolithically fabricated on blue/green dual‐wavelength LED epilayers, using red quantum dot photoresist as a color converter. Pure RGB emission and a wide color gamut are achieved, as shown by electroluminescence spectra. Full‐color patterns with controllable grayscale and color mixing can be clearly rendered driven by a full‐color microdisplay controller, indicating tremendous potential of this novel approach for full‐color LED microdisplays in the future.

No abstract

No abstract

An electromagnetic acoustic transducer (EMAT) is suitable for measuring the propagation time more accurately without causing abrasion to the transducer during testing due to the principle of its excitation. This work designs a flux-concentrating EMAT with a radial-flux-focusing permanent magnet to significantly enhance static magnetic field strength. Through theoretical analysis and finite element simulation, two kinds of coils are designed according to the concentration areas of the horizontal and vertical components of the magnetic field. One is used to generate pure longitudinal waves, and the other is used to generate both longitudinal waves and shear waves. The experimental comparison shows that the amplitudes of the pure longitudinal wave and the dual-mode wave excited by the two kinds of coils with the radial-flux-focusing magnet are more than two times higher than those with the ordinary magnet. Therefore, the flux-concentrating EMAT with the appropriate coil provides an insight into realizing more accurate detection where longitudinal wave detection is required.

No abstract