Optical phased arrays (OPAs) are renowned for their exceptional ability to manipulate and direct light beams, positioning them as an ideal choice for solid-state light detection and ranging (LiDAR) technologies. This review provides a comprehensive examination of the current research landscape for photonic integrated circuit (PIC)-based OPAs. It begins by addressing the critical design elements at the component level necessary for optimal functionality. This review then delves into phase calibration techniques and the overarching architecture of OPAs. It concludes by emphasizing the innovative 3-D OPA design, which stands out for its enhanced optical efficiency.

In this paper, we proposed an interdigitated capacitor (IDC)-based glucose biosensor to measure different concentrations of glucose from 1 μM to 1 M. We studied four different types of solvatochromic dyes: Auramine O, Nile red, Rhodamine B, and Reichardt’s dye (R-dye). These dyes were individually incorporated into a polymer [polyvinyl chloride (PVC)] and N,N-Dimethylacetamide (DMAC) solution to make the respective dielectric/sensing materials. To the best of our knowledge, we report for the first time an IDC glucose biosensing system utilizing a solvatochromic-dye-containing sensing membrane. These four dielectric or sensing materials were individually placed into the interdigitated electrode (IDE) by spin coating to make four IDC glucose biosensing elements. The proposed IDC glucose biosensor has a high sensing ability over a wide dynamic range and its sensitivity was about 23.32 mV/decade. It also has fast response and recovery times of approximately 7 s and 5 s, respectively, excellent reproducibility with a standard deviation of approximately 0.023, highly stable sensing performance, and real-time monitoring capabilities. The proposed IDC glucose biosensor was compared with an IDC, potentiometric, FET, and fiber-optic glucose sensor with respect to response time, dynamic range width, sensitivity, and linearity. We observed that the designed IDC glucose biosensor offered excellent performance.

In this paper, an electronic tongue/taste sensor array containing different interdigitated capacitor (IDC) sensing elements to detect different types of tastes, such as sweetness (glucose), saltiness (NaCl), sourness (HCl), bitterness (quinine-HCl), and umami (monosodium glutamate) is proposed. We present for the first time an IDC electronic tongue using sensing membranes containing solvatochromic dyes. The proposed highly sensitive (30.64 mV/decade sensitivity) IDC electronic tongue has fast response and recovery times of about 6 s and 5 s, respectively, with extremely stable responses, and is capable of linear sensing performance (R² ≈ 0.985 correlation coefficient) over the wide dynamic range of 1 µM to 1 M. The designed IDC electronic tongue offers excellent reproducibility, with a relative standard deviation (RSD) of about 0.029. The proposed device was found to have better sensing performance than potentiometric-, cascoded compatible lateral bipolar transistor (C-CLBT)-, Electronic Tongue (SA402)-, and fiber-optic-based taste sensing systems in what concerns dynamic range width, response time, sensitivity, and linearity. Finally, we applied principal component analysis (PCA) to distinguish between various kinds of taste in mixed taste compounds.

This study investigates the role of pitch size in achieving high numerical aperture (NA) and focusing efficiency in metalens design, while demonstrating how high refractive index materials contribute to performance enhancement by enabling smaller pitch sizes through reduced filling ratios. Silicon-rich nitride (SRN) was chosen as the material platform due to its high refractive index, CMOS compatibility, and cost-effective fabrication. Two SRN-based metalenses were designed: a geometric phase metalens (GPM) and a propagation phase metalens (PPM), each evaluated at aspect ratios of 10:1 and 4:1. The GPM achieved an NA of 0.99 with focusing efficiencies of 26.6% (10:1) and 17.6% (4:1), while the PPM achieved NAs of 0.95 (10:1) and 0.97 (4:1) with focusing efficiencies of 65.6% and 32.1%, respectively. Our findings demonstrate that smaller pitch sizes reduce spatial discretization errors, enhancing phase fidelity and focusing efficiency, which is applicable to various applications such as imaging and polarimetry.

A passive radio frequency-identification-based inductor-capacitor (LC) lactate sensory system with a specific dye-containing interdigitated capacitor (IDC) in which the sensing signal is amplified by the solvatochromic effect is proposed. When a lactate solution contacts the IDC of the LC lactate sensor, the capacitance of the IDC changes, changing the resonance frequency of the sensor. This changes the oscillation frequency of the Colpitts oscillator in the readout circuit. By analyzing the frequency changes, the concentration of the lactate solution can be measured quickly and accurately over a wide range. To our knowledge, the proposed device is the first passive, battery-free LC lactate sensor that uses solvatochromic dye-containing IDC sensing elements to detect lactate solution concentrations. Four solvatochromic dyes were tested and incorporated into a polymer as the lactate-sensitive membranes of the IDCs. The proposed LC sensor tag offers excellent sensitivity and linearity over a wide lactate concentration range of about $10 \mu \text{M}$ to 1 M. The response and recovery times of our LC sensory system were significantly shorter than those of previously reported lactate sensors. Our results are useful for the development of reliable wearable devices capable of real-time lactate detection at a low cost.