Micromirrors have recently emerged as an essential component in optical scanning technology, attracting considerable attention from researchers. Their compact size and versatile capabilities, such as light steering, modulation, and switching, are leading them as potential alternatives to traditional bulky galvanometer scanners. The actuation of these mirrors is critical in determining their performance, as it contributes to factors such as response time, scanning angle, and power consumption. This article aims to provide a thorough exploration of the actuation techniques used to drive micromirrors, describing the fundamental operating principles. The four primary actuation modalities—electrostatic, electrothermal, electromagnetic, and piezoelectric—are thoroughly investigated. Each type of actuator’s operational principles, key advantages, and their limitations are discussed. Additionally, the discussion extends to hybrid micromirror designs that combine two types of actuation in a single device. A total of 208 closely related papers indexed in Web of Science were reviewed. The findings indicate ongoing advancements in the field, particularly in terms of size, controllability, and field of view, making micromirrors ideal candidates for applications in medical imaging, display projections, and optical communication. With a comprehensive overview of micromirror actuation strategies, this manuscript serves as a compelling resource for researchers and engineers aiming to utilize the appropriate type of micromirror in the field of optical scanning technology.

This paper presents a bi-port, single-layered (planar), dual circularly polarized (CP) patch antenna with improved interport isolation for S-band satellite telemetry and telecommand applications. The dual-port, planar antenna is based on a square-shaped radiator with trimmed corner to achieve CP characteristics (RHCP and LHCP) for excitations from respective ports. However, the RF isolation between the two ports is very low due to strong power leakage from transmit (T_x) to transmit (R_x) port. The externally employed tunable self-interference cancellation (SIC) circuit achieves high isolation between orthogonal ports while axial ratio (AR) is 3dB for both right and left handed circular polarization modes. The employed single-tap SIC circuit/loop attains the high interport isolation through signal inversion mechanism. The proposed antenna design achieves 72dB peak interport isolation in addition to 30dB and 15dB port to port isolation over the isolation or SIC bandwidths of 15MHz and 90MHz (10dB bandwidth for both ports), respectively. The port to port isolation performance is improved without significant degradation in antenna radiation characteristics. The validation model of the presented planar antenna based on single element characterizes much better measured interport isolation performance compared to those dual CP printed antennas reported earlier as endorsed through detailed comparison

This article presents a new wafer-bonding fabrication technique for Capacitive Micromachined Ultrasonic Transducers (CMUTs) using polymethyl methacrylate (PMMA). The PMMA-based single-mask and single-dry-etch step-bonding device is much simpler, and reduces process steps and cost as compared to other wafer-bonding methods and sacrificial-layer processes. A low-temperature (< $180{}^{\circ }\mathrm{C}$ ) bonding process was carried out in a purpose-built bonding tool to minimize the involvement of expensive laboratory equipment. A single-element CMUT comprising 16 cells of 2.5 $\mathrm{mm}$ radius and 800 $\mathrm{nm}$ cavity was fabricated. The center frequency of the device was set to 200 kHz for underwater communication purposes. Characterization of the device was carried out in immersion, and results were subsequently validated with data from Finite Element Analysis (FEA). Results show the feasibility of the fabricated CMUTs as receivers for underwater applications.