You-Chia Chang

Focal plane arrays (FPAs) promise robust solid‐state beam steering for LiDAR and free‐space optical communications. However, the need for external collimation lenses hinders chip‐scale compactness. Discrete switching between FPA elements further introduces blind spots and limits the number of resolvable points, restricting applications that require continuous tracking. Here, we demonstrate a silicon photonic beam steerer based on a metalens FPA that monolithically integrates the collimation lens on‐chip. Thermo‐optic prisms enable continuous fine‐tuning, eliminating blind spots and doubling the number of resolvable points. Continuous steering over a 62° field of view is achieved while maintaining high beam quality, with an average sidelobe suppression ratio of 19 dB.

This study optimizes photonic nanojet (PNJ)‐amplified surface‐enhanced Raman spectroscopy (SERS) by precisely controlling the gap distance between a dielectric microsphere and the SERS‐active surface, ensuring alignment of the PNJ focal point with plasmonic hotspots. To achieve this, we developed a tunable sensing platform using poly(ethylene glycol) diacrylate (PEGDA) microcone arrays decorated with silver nanoparticles (AgNPs). These microcone arrays mechanically support high refractive index microspheres at specific heights above the SERS substrate, allowing the microsphere‐substrate gap to be systematically tuned by varying the microcone pitch. Structural parameters were validated using 3D optical profilometry, and the PNJ focal distances were modeled using finite‐difference time‐domain (FDTD) simulations to confirm optimal alignment. Our findings demonstrate that an optimal gap distance exists for each microsphere size, corresponding to the precise alignment of the PNJ's focal point with the SERS‐active surface. This optimized configuration yields a PNJ‐induced SERS enhancement of up to 15‐fold, significantly improving the limit of detection for adenine (to 1 nM) and melamine (to 0.5 µ M ). Overall, this work establishes microcone‐mediated gap control as an effective, reproducible strategy for the rational design and optimization of PNJ‐amplified SERS biosensors, with potential applications in food safety, environmental monitoring, and biomedical diagnostics.

We experimentally demonstrate a silicon photonic physical unclonable function based on a waveguide array and phase shifters embedded in feedback loops. We show that optical feedback enhances the unpredictability against machine learning attacks.

We demonstrate a focused beam scanner based on an 8×8 active optical phased array, achieving continuous steering throughout a 3D volume. The device requires only single-point calibration, removing the need for time-consuming iterative optimization.

Model-based optical proximity correction (OPC) is a widely adopted resolution enhancement technique that compensates for lithography proximity effects by adjusting and correcting mask pattern shapes. However, its application to large-area, high-density patterns such as metasurfaces is constrained by the computational demands of image calculation in the lithographic model. This paper introduces an intelligent proximity correction (IPC) system that leverages a deep-learning U-net-based lithographic model to optimize mask designs through iterative algorithms. By eliminating the need for optical calculations while maintaining accurate predictions of photoresist contours directly from mask patterns, the intelligent lithography model demonstrated a 3-fold reduction in simulation time compared to conventional optical models. Overall the IPC system with parallel computation achieves a remarkable 35-fold speed increase compared to conventional OPC approaches without compromising correction accuracy. Experimental results demonstrate that IPC is effective in fabricating high-efficiency, large-area metalenses and metasurface holograms for the visible wavelength using KrF photolithography, opening possibilities to produce complex, large-scale metasurfaces for various applications in optics and photonics.

Enlarging the active window size of the photodetector (PD) while sustaining its high-speed and high-responsivity performances is the key to achieving a high-performance photo-receiver with a large field-of-view (FoV) angle for application in a free space laser communication system. However, in the traditional PD structure, a large active area always leads to a pronounced degradation in the RC-bandwidth. Using a tandem layout for high-speed p-i-n PD arrays solves the problem, but it reduces the responsivity for high-speed and large FoV performance, as current balancing between the different p-n junctions is needed. Here, for the first time, novel tandem APD arrays are demonstrated which relax the fundamental trade-offs among window size, responsivity, and speed. Our flip-chip packaged 3 $ \times $ 3 arrays with a window size of 0.12 mm can simultaneously achieve a, high-responsivity (1.2 A/W), wide-bandwidth (6 GHz), and large GBP (150 GHz).

We put forward and demonstrate a 2D wide field-of-view (FOV) silicon photonics (SiPh) optical beam steerer via a metalens focal plane array (FPA). We illustrate the potential implementations of the SiPh metalens based FPA for chip-to-chip optical wireless communication (OWC). Experimental results show that the measured FOV is 51.4° × 6.12°, and the average full-width at half-maximum (FWHM) divergence angle is 1.4°. Bit-error-rate (BER) measurements using optical orthogonal frequency division multiplexing (OFDM) signals reveal that, while steering the beam and transmitting data at over 70 Gbit/s, the system can fulfill the hard-decision forward error correction (HD-FEC) bit-error-rate (BER) requirement of 3.8 × 10⁻³. We also discuss the potential of using liquid-crystal (LC) based spatial-light-modulator (SLM) as the reflective surface for the chip-to-chip OWC transmission and optical beam manipulation.

In this study, design high-speed avalanche photodiodes (APDs) with wide dynamic range performance which are poised to play an important role in the next generation of wireless communication systems, especially those incorporating a 50 G passive optical network (PON) as a backbone. We demonstrate that the DC responsivity of advanced high-speed APDs with a cascaded M-layer design can be enhanced by enlarging the spot size of the launched optical beam and increasing the working distance without compromising their high-speed performance. The optimization is effective for both top- and backside-illuminated structures with buried optical reflectors. Furthermore, under low gain operation (∼2), when illuminated with an optimized beam shape, the backside-illuminated APD can achieve a broad optical-to-electrical (O-E) bandwidth of 35 GHz, maintaining a low excess noise factor (∼1.5) and high responsivity (1.6 A/W; 0.9 V_br) even near saturation output levels of photocurrent (5 mA) and MMW power at 35 GHz. This exceptional high-speed performance together with the wide dynamic range of the APD demonstrated under the optimized optical coupling scheme is crucial for dense deployment scenarios in MMW wireless communication networks with a fiber backbone.

Silicon photonic physical unclonable function (PUF) stands out as a promising hardware security primitive, offering the advantages of CMOS compatibility and a compact chip-scale footprint compared to other optical PUFs. It harnesses inherent fabrication variations arising during mass production to generate unique digital keys. In this paper, we experimentally demonstrate a silicon photonic PUF using an 8-channel waveguide array with embedded phase shifters, enabling the active generation of challenge-response pairs. Through testing six device copies fabricated on the same wafer, we achieve a false acceptance rate of 4.06 × 10⁻²¹. Both challenge generation and response detection can be performed on-chip, leading to a stand-alone PUF on the silicon photonic platform.

Squeezed light, with its quantum noise reduction capabilities, has emerged as a powerful resource in quantum information processing and precision metrology. To reach noise reduction levels such that a quantum advantage is achieved, off-chip squeezers are typically used. The development of on-chip squeezed light sources, particularly in nanophotonic platforms, has been challenging. We report 3.7±0.2dB of directly detected nanophotonic quantum squeezing using foundry-fabricated silicon nitride (Si₃N₄) microrings with an inferred squeezing level of 10.2 dB on-chip. The squeezing level is robust across multiple devices and pump detunings, and is consistent with the overcoupling degree without noticeable degradation from excess classical noise. We also offer insights to mitigate thermally induced excess noise, which typically degrades squeezing, by using small-radius rings with a larger free spectral range (450 GHz) and consequently lower parametric oscillation thresholds. Our results demonstrate that Si₃N₄ is a viable platform for strong quantum noise reduction in a CMOS-compatible, scalable architecture.