Solar-blind ultraviolet (UV) photodetectors (PDs) based on $\boldsymbol {\beta }$ -Ga2O3 hold considerable promise for both military and civilian applications owing to their wide bandgap and excellent stability. However, light absorption in the Ga2O3 layer is significantly reduced by surface metal electrodes, thereby limiting quantum efficiency. Here, we report a combined theoretical and experimental study of solar-blind UV metal–semiconductor–metal (MSM) Ga2O3 PDs incorporating Ti/Au nanogratings. Simulations reveal that the nanogratings excite localized surface plasmon resonance (LSPR), effectively enhancing light absorption in the Ga2O3 layer. The fabricated devices achieve external quantum efficiencies (EQEs) of $10^{6}$ %– $10^{7}$ %, substantially outperforming conventional MSM PDs with interdigital electrodes. Furthermore, we demonstrate that grating width critically regulates LSPR, with the optimized device achieving a responsivity (R) of $1.14 \times {{10}^{5}} \mathrm {A}\cdot \mathrm {{W}^{-1}}$ , an EQE of 5.57% $\times{\,} {10}^{{7}}$ %, and a specific detectivity ( $\mathrm {D}^{*}$ ) of ${{3.01}} \times {{10}^{12}}$ Jones. These findings provide design guidelines for plasmonic nanogratings and a promising strategy for high-performance solar-blind UV PDs.
Lead zirconate titanate (PZT)-based piezoelectric MEMS micromirrors are highly desirable for their high responsivity, high speed, and low power, but their achievable scan range is fundamentally limited by the large nonlinearities arising from the ferroelectric properties of PZT, especially under high-voltage excitation. In this work, a DC-biasing strategy is proposed to suppress the nonlinearity and extend the usable scan range without the need to modify the device structure or material composition. A piezoelectric micromirror with Z-shaped PZT actuators and a $1\times 1$ mm mirror aperture is designed and fabricated. The nonlinear scanning behaviors of the micromirror are systematically studied under various DC bias voltages in both low-frequency and resonant operation modes. Under low-frequency operation, the effects of DC bias are investigated over a voltage range of −20 to + 20 V. Under a −15 V DC bias, the optical scan angle reaches ±6.5° at 50 Vpp at 10 Hz, a threefold increase compared with that without DC bias, and achieves a linearity of ${\mathrm {R}}^{{2}} =0.997$ , compared with ${\mathrm {R}}^{{2}} =0.887$ under the unbiased condition. Under resonant operation, a −15 V DC bias increases the optical scan angle to ±38.3° at 30 Vpp excitation and the resonant frequency of 1.35kHz, corresponding to a 58% enhancement compared with the unbiased condition. The effectiveness of DC bias is strongly dependent on the bias polarity. A bias aligned with the initial polarization shifts the polarization response away from the coercive field and suppresses ferroelectric polarization switching. These results establish DC-biasing as an effective approach for achieving large-angle and high-linearity optical scanning.
An innovative ammonia (NH ${}_{{3}}\text {)}$ gas sensor is fabricated by integrating a sputtered tungsten-doped indium oxide (IWO) thin film with evaporated platinum nanoparticles (Pt NPs) and deposited on a sapphire substrate. The inclusion of Pt NPs significantly enhances the performance of the sensor in detecting NH3, leveraging their catalytic properties to increase sensitivity. Extensive analyses were conducted to characterize the compositional, elemental, and structural properties of the sensor, providing valuable insights into its enhanced sensing capabilities. Steady-state current–voltage ( $I$ – $V$ ) and transient current–time (I–t) measurements were meticulously recorded to investigate the NH3 gas-sensing behavior comprehensively. Under operational conditions of $200^{\circ }$ C, when exposed to 1000 ppm NH3 in air, the studied sensor exhibited a remarkable response of 142. It demonstrated a response time of 177 s and a recovery time of 49 s. Impressively, the sensor can detect lower concentrations, down to 1 ppm NH3, showcasing its wide detection range. To understand the sensing mechanism, an investigation into the adsorption of NH3 molecules on the surface of the sensor was conducted. This analysis shed light on the phenomena related to surface coverage and gas interaction. The studied sensor also shows promising selectivity toNH3 gas.
To preserve a large beam tunnel and maintain a high beam transmission ratio in the terahertz (THz) band, a frequency multiplier based on superradiant Smith–Purcell radiation (SSPR) from a grooved subwavelength hole array (GSHA) is proposed. Compared with the conventional subwavelength hole array (CSHA), the GSHA offers a larger characteristic impedance ${R}/{Q}$ and stronger radiation, while its beam tunnel radius is more than twice that of conventional 660-GHz devices. Under the same operating conditions, PIC simulations show that the output power of the proposed GSHA-based multiplier is more than 2.8 times that of the CSHA. Without phase velocity taper (PVT), it achieves a peak output power of 72 mW at 660.2 GHz with a −3-dB bandwidth of 2.6 GHz. By tuning the input power, the −3 dB bandwidth is extended to 3.2 GHz (659.2–662.4 GHz). With PVT, the peak output power reaches 111 mW. Cold-test results demonstrate that the fabricated modified folded waveguide (MFWG) slow wave structure (SWS) exhibits a reflection coefficient below −15 dB across 328.3–336.0 GHz, along with well-matched transmission characteristics. Meanwhile, the measured and simulated results of the GSHA exhibit excellent agreement within the 655–665-GHz range. These results indicate that the GSHA-based frequency multiplier offers an effective solution to the challenge of implementing electron optical systems (EOSs) for THz vacuum electronic devices (VEDs).
