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Yasha Yi

Publications and source records attributed to Yasha Yi.

13 recordsLinked to original sources
arXiv2026

3D optoelectronics and co-packaged optics: when solving the wrong problems stalls deployment

The rapid growth of AI and accelerator-driven workloads is forcing a fundamental rethinking of optical interconnect architectures in datacenters. Co-packaged optics and three-dimensional photonic integration have emerged as promising solutions to overcome the energy and bandwidth limitations of electrical I/O. Yet, as optics move closer to compute, packaging, thermal management, and system-level robustness increasingly dominate performance and scalability. Here, we argue that co-packaged optics should not be viewed as a component-level optimization, but as an architectural commitment that reshapes the boundaries between photonics, electronics, and system design. We examine how heterogeneous integration strategies, chiplet-based optics, and emerging packaging platforms redefine scaling laws for AI systems, often introducing trade-offs that are underappreciated in device-centric analyses. Looking forward, we discuss why standardization, serviceability, and thermal-aware co-design will be decisive in determining whether co-packaged optics can transition from early deployment to widespread adoption in AI-scale datacenters.

physics.optics↗
arXiv2025

Multi-NA Metalens Array for Compact High-NA Microscopy

We demonstrate a CMOS-compatible silicon-rich nitride metalens array for visible microscopy at 660 nm. Three co-planar elements provide numerical apertures of 0.54, 0.92, and 0.97, enabling within-sample NA benchmarking without objective swaps. Imaging of annular cell monolayers labeled in the AF647 ZO-1 channel shows progressive sharpening of junctional edges and reduced blur with increasing NA, consistent with diffraction-limited scaling. The compact, planar platform supports direct integration with image sensors, offering a practical route to high-NA fluorescence bioimaging in space-constrained, low-cost systems.

physics.optics↗
arXiv2025

Polarization-Resolved Chlorophyll Imaging for Non-Invasive Plant Tissue Assessment Using a Silicon-Rich Nitride Metalens Array

Polarization-sensitive imaging enhances contrast and reveals structural features in biological tissues that are often missed by intensity-based methods, but its adoption is limited by bulky optics. We present a compact silicon-rich nitride (SRN) metalens array for high-resolution, polarization-resolved imaging of plant tissue at the chlorophyll absorption peak (660\,nm). The array integrates orthogonally sensitive metalenses to simultaneously capture X- and Y-linearly polarized transmission images, enabling real-time, label-free assessment of plant microstructure and stress responses. Polarization fusion and difference mapping reveal structural anisotropy and pigment variation in both healthy and stressed leaves. The SRN metalens, designed via an inverse approach using birefringent meta-atoms and fabricated through CMOS-compatible processes, achieves a large numerical aperture, high transmission, and spectral alignment with biological absorbers. This work demonstrates the feasibility of compact, integrated polarization-resolved imaging, offering a scalable alternative to conventional systems. The approach holds potential for biomedical and agricultural applications, where detecting subtle polarization-dependent changes could enable early diagnosis and tissue characterization

physics.optics↗
arXiv2024

Dual-Axis Beam-Steering OPA with purely Passive Phase Shifters

In this work, we present a multi-layer optical phased array (OPA) designed for dual-axis beam steering on a silicon (Si) platform, utilizing only wavelength tuning. Our design eliminates the need for grating couplers, commonly required for dual-axis beam steering, thereby reducing energy losses due to substrate leakage. It also features the unique capability of achieving a positive or negative phase slope profile. This three-dimensional architecture enhances output efficiency by emitting light from the device edge, providing greater flexibility and improved performance in beam steering. This approach opens up new possibilities for on-chip photonic systems, enabling faster, more accurate, and broader beam steering range.

physics.optics↗
arXiv2024

Polarization-based Metalenses with High Numerical Aperture and Focusing Efficiency Utilizing Silicon-rich Nitride

We explore the cutting-edge application of silicon-rich nitride (SRN) in the realm of high numerical aperture (NA) metalens design, focusing on the crucial role of pitch size optimization in amplifying lens efficiency through advanced simulations. Our investigation unveils how the exceptional tunable high refractive index of SRN can be harnessed to achieve significant advancements in metalens performance. By meticulously designing and simulating two innovative SRN-based metalenses - Mk1, with an NA of 0.9, reaching an impressive 75% focusing efficiency with full width at half maximum (FWHM) of 0.53λ, and Mk2, with an NA of 0.99, achieving a 42% efficiency while maintaining an FWHM of 0.48λ. We demonstrate the critical influence of reduced pitch size on enhancing efficiency. This study not only highlights the unparalleled potential of SRN in optimizing metalens efficiency but also represents a significant leap forward in the field of nanophotonics, offering new pathways for the development of highly efficient flat photonic devices.

physics.optics↗
arXiv2024

Passive Aperiodic Optical Phased Array based on Uniform Random Shuffle

Grating lobes arise from the periodic nature of element spacing in the optical phased array. Essentially, the phased array performs the Spatial Fourier Transform on light; the steering capability of the main lobe is governed by phase shift variations among waveguides, and the Sidelobe Suppression Ratio (SLSR) correlates with the uniformity of emitter positions. Leveraging this understanding, we have optimized a 1x64 channel passive aperiodic OPAs with the uniform random shuffle in the emitter's position. Our conceptual simulations highlight a robust steering capability (18.60° / 10nm) and SLSR (-13.46 dB @ 0° / -8.27 dB @ +/-45°), and initial measurements demonstrate the steering capability (9.8 ° / 10nm, with smaller phase shifts design) and SLSR (-6.1dB @ -33.4°) from the preliminary fabrication.

physics.app-ph↗
arXiv2022

Photonic integrated circuit with multiple waveguide layers for broadband high-efficient on-chip 3-D optical phased arrays in light detection and ranging applications

Traditional photonic integrated circuit (PIC) inherits the mature CMOS fabrication process from the electronic integrated circuit (IC) industry. However, this process also limits the PIC structure to a single-waveguide-layer configuration. In this work, we explore the possibility of the multi-waveguide-layer PIC by proposing and demonstrating a true 3-D optical phased array (OPA) device, with the light exiting from the edge of the device, based on a multi-layer Si3N4/SiO2 platform. The multi-waveguide-layer configuration offers the possibility of utilizing edge couplers at both the input and the emitting ends to achieve broadband high efficiency. This uniqueness provides the potential for a more extended detection range in the Lidar application. The device has been studied by numerical simulation, and proof-of-concept samples have been fabricated and tested with a CMOS-compatible process. To the best of our knowledge, this is the first experimental proof-of-concept of a true 3-D OPA with a multi-waveguide-layer configuration all over the device.

physics.optics↗
arXiv2019

High efficiency end-fire 3-D optical phased array based on multi-layers Si3N4/SiO2 platform

Beam steering device such as optical phased array (OPA) is a key component in applications of solid-state Lidar and wireless communication. The traditional single-layer optical phased array (OPA) results in a significant energy loss due to the substrate leakage caused by the downward coupling from the grating coupler structure. In this work we have investigated a structure based on multi-layers Si3N4/SiO2 platform that can form a 3-D OPA to emit the light from the edge of the device with high efficiency, a 2-D converged out-coupling beam will be end-fired to the air. The high efficiency and wide horizontal beam steering are demonstrated numerically, the influence of vertical cross-talk, the delay length, number of waveguide layers, and the fabrication feasibility are also discussed.

physics.app-ph↗
arXiv2019

Metalens With Artificial Focus Pattern

Metalens as one of the most popular applications of emmerging optical metasurfaces has raised widspread interest recently. With nano structures fully controlling phase, polarization and transmission, metalens has achieved comparable performance of commercial objective lenses. While recent studies seeking for the accomplishment of traditional focusing behaviors through metalens are successful, inthis work, we have discovered that instead of focusing light to a point, metasurface further enables shaping the focus into a flexibly designed pattern, with more promises and potentials. New mechanism and generalizations of conventional point-focused metalens guiding principles have been proposed with metalens concentrating light to artificial focus pattern. As proving examples, we have demonstrated the engineering of metalens with artificial focus pattern by creating line and ring-shaped focus as 'drawing tools'. The metalens with 'U' and 'M' shaped focus are characterized for the proof of concepts. These metalens are fabricated through a single layer of silicon-based material through CMOS compatible nano fabrication process. The mechanism to generate artificial focus pattern can be applied to a plethora of future on-chip optical devices with applications ranging from beam engineering to next generation nano lithography.

eess.IV↗
arXiv2011

Graded index and randomly oriented core-shell silicon nanowires with broadband and wide angle antireflection for photovoltaic cell applications

Antireflection with broadband and wide angle properties is important for a wide range of applications on photovoltaic cells and display. The SiOx shell layer provides a natural antireflection from air to the Si core absorption layer. In this work, we have demonstrated the random core-shell silicon nanowires with both broadband (from 400nm to 900nm) and wide angle (from normal incidence to 60\degree) antireflection characteristics within AM1.5 solar spectrum. The graded index structure from the randomly oriented core-shell (Air/SiOx/Si) nanowires may provide a potential avenue to realize a broadband and wide angle antireflection layer.

physics.optics↗
arXiv2011

Higher-order optical resonance node detection of integrated disk microresonator

We have demonstrated higher-order optical resonance node detection by using an integrated disk microresonator from through port of the coupling bus waveguide. In addition to the fundamental mode, the disk resonator has higher-order whispering gallery modes. The excited second-order higher-order mode has a node at the position where the electromagnetic energy of the fundamental mode is close to a maximum. This high resolution measurement of optical resonance mode profile has a variety of applications for optical sensing and detection. The self-referencing characteristics of the two optical resonance modes have potential to achieve optical detection independent of external perturbation, such as temperature change.

physics.optics↗
arXiv2010

Metallic nanoparticle on micro ring resonator for bio optical detection and sensing

We have investigated the unique effects of metallic nanoparticle on the ring resonator, especially multiple Au nanoparticles on the micro ring resonator with the 4-port configuration on chip. For the Au nanoparticle, because it has smaller real refractive index than air and large absorption refractive index, we found that there is a blue shift for the ring resonance wavelength, instead of red shift normally observed for dielectric nanoparticles. The drop port intensity is strongly dependent on both number and size of nanoparticles, while relatively independent on position of nanoparticles. The correlation between the penetration depth of Au and the resonance mode evanescent tail is also discussed to reveal the unique properties of Au nanoparticle to be used for detection, sensing and nano medicine.

physics.optics↗