Viscoelastic initially stressed microbeam heated by an intense pulse laser via photo-thermoelasticity with two-phase lag

This work aims to assess the response of viscoelastic Kelvin–Voigt microscale beams under initial stress. The microbeam is photostimulated by the light emitted by an intense picosecond pulsed laser. The photothermal elasticity model with dual-phase lags, the plasma wave equation and Euler–Bernoulli beam theory are utilized to construct the system equations governing the thermoelastic vibrations of microbeams. Using the Laplace transform technique, the problem is solved analytically and expressions are provided for the distributions of photothermal fields. Taking aluminum as a numerical example, the effect of the pulsed laser duration coefficient, viscoelasticity constants and initial stress on photothermal vibrations has been studied. In addition, a comparison has been made between different models of photo-thermoelasticity to validate the results of the current model. Photo-microdynamic systems might be monolithically integrated on aluminum microbeams using microsurface processing technology as a result of this research.

Terahertz-wave detector on silicon carbide platform

We developed a novel terahertz-wave detector fabricated on a SiC platform implementing an InP/InGaAs Fermi-level managed barrier (FMB) diode. The FMB diode epi-layers were transferred on a SiC substrate, and a waveguide coupler and filters were monolithically integrated with an FMB diode. Then, fabricated detector chip was assembled in a fundamental mixer module with a WR-3 rectangular-waveguide input port. It exhibited a minimum noise equivalent power as low as 3e-19 W/Hz at around 300 GHz for a local oscillator power of only 30 microwatts.

Monolithically integrated green-to-orange color InGaN-based nanocolumn photonic crystal LEDs with directional radiation beam profiles

In this study, the monolithic integration of LEDs with different emission colors (wavelengths of 543, 573, and 597 nm) with the directional radiation profiles was demonstrated. InGaN/GaN nanocolumn arrays ordered in a triangular lattice were prepared side by side, changing the diameter of the n-GaN nanocolumn (Dn-GaN). The periodic arrangement of the nanocolumns led to the photonic crystal (PC) effect. The photonic band edge wavelength (λB) and the InGaN bandgap were controlled by the Dn-GaN. By controlling λB closely at the bandgap wavelength, the PC effect provided directional beam radiation from the LEDs with radiation angles of approximately ±30°

Enhancing AlN PMUTs’ Acoustic Responsivity within a MEMS-on-CMOS Process

In this paper, guidelines for the optimization of piezoelectrical micromachined ultrasound transducers (PMUTs) monolithically integrated over a CMOS technology are developed. Higher acoustic pressure is produced by PMUTs with a thin layer of AlN piezoelectrical material and Si3N4 as a passive layer, as is studied here with finite element modeling (FEM) simulations and experimental characterization. Due to the thin layers used, parameters such as residual stress become relevant as they produce a buckled structure. It has been reported that the buckling of the membrane due to residual stress, in general, reduces the coupling factor and consequently degrades the efficiency of the acoustic pressure production. In this paper, we show that this buckling can be beneficial and that the fabricated PMUTs exhibit enhanced performance depending on the placement of the electrodes. This behavior was demonstrated experimentally and through FEM. The acoustic characterization of the fabricated PMUTs shows the enhancement of the PMUT performance as a transmitter (with 5 kPa V−1 surface pressure for a single PMUT) and as a receiver (12.5 V MPa−1) in comparison with previously reported devices using the same MEMS-on-CMOS technology as well as state-of-the-art devices.

Growth of Pseudomorphic GeSn at Low Pressure with Sn Composition of 16.7%

Group-IV alloy GeSn holds great promise for the high-performance optoelectronic devices that can be monolithically integrated on Si for near- and mid-infrared applications. Growth of GeSn using chemical vapor deposition technique with various Sn and Ge precursors has been investigated worldwide. To achieve relatively high Sn incorporation, the use of higher pressure and/or higher order Ge hydrides precursors were reported. In this work, we successfully demonstrated the growth of high-quality GeSn with Sn composition of 16.7% at low pressure of 12 Torr. The alloy was grown using the commercially available GeH4 and SnCl4 precursors via a chemical vapor deposition reactor. Material and optical characterizations were performed to confirm the Sn incorporation and to study the optical properties. The demonstrated growth results reveal a low-pressure growth window to achieve high-quality and high Sn alloys for future device applications.

Monolithically-integrated 3D printed coaxial bandpass filters and RF diplexers: single-band and dual-band

The manuscript reports on additively-manufactured (AM) coaxial-resonator-based bandpass filters (BPFs) and RF diplexers. A monolithic integration concept using stereolithography apparatus (SLA) is proposed and discussed in detail. Coupled-resonator-based synthesis alongside full-electromagnetic-based design methods is used for the design of the monolithic filters and RF diplexers. In particular, the paper discusses a new external coupling mechanism for dual-band BPFs that allow to independently control the coupling in each of the BPF passbands. Furthermore, a novel coaxial transmission line-type T-junction is proposed for the design of single- and dual-band RF diplexers. For practical validation purposes, multiple BPF and RF diplexer prototypes were designed, manufactured and tested at S- and C-band demonstrating the applicability of the proposed concept to low-cost, low-loss and low-weight RF components with complex geometrical features.