This PDF file contains the front matter associated with SPIE Proceedings Volume 12432, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Silicon photomultiplier (SiPMs) is a photon counting device that consists of single photon avalanche diodes (SPADs) arrays being operated at a Geiger mode and has been widely used in many kinds of application including high-energy physics, confocal laser scanning microscopy (CSLM), flow cytometry, and light detection and ranging (LiDAR) instead of photomultiplier tube (PMT). Trench structures basically places at the boarder of every SPAD to guard optical and electrical crosstalk. However, illuminating photons to the trench region restricted the performance of SiPM such as photon detection efficiency (PDE) and timing performance because it does not absorb photon sufficiently. Our previous work demonstrated that guiding incident photons into the photo sensitive area of SPADs using metalens array resulted in improvement of the performance of the SiPM. However, performance is expected to fluctuate due to misalignment caused by slight vibration because metalens and SiPMs are separated configuration. Guaranteeing a good alignment between the metalens and SiPM has been necessary for practical applications. Here, we demonstrate the completely monolithic integration of a metalens with its corresponding SPAD to provide stable PDE improvement while maintaining the compact and flatness of the optical device. Furthermore, we investigated the crosstalk and dark-current comparing with a reference SiPM without the metalens for investigating the negative effect of integrating metalens with the SiPM. From the results of sophisticated investigation, we show the more practical approach toward the improving overall performance of the SiPM not only the PDE and timing performance but also crosstalk and dark current. Finally, we will show our next perspective and progress towards near infrared application.

Phase-change materials offer a compelling platform for low power consumption active integrated optical circuits and meta optics, with their large optical index contrast (Δn, Δk) and nonvolatile phase transition^1,2. Here, we demonstrate an electrically driven tunable meta lens in telecom range by exploring the full potential of a low absorption loss and high refractive index contrast PCM alloy, Sb₂Se_3, to realize non-volatile, reversible, fast focusing and defocusing meta lens in the 1550 telecom spectral range. With a fixed geometric design, the phase change material of Sb₂Se₃ switches the focusing length of a silicon photonic meta lens between two different values nonviolently. This unique functionality of the hybrid meta surface is attributed to the fact that the silicon’s refractive index is in the middle of the two convertible states in the optical phase change material. The transparency of Sb₂Se₃ in both states enables near phase-only meta surface structures. Our heterostructure architecture capitalizes over the integration of a robust resistive transparent microheater ITO (Indium Tin Oxide) decoupled from meta lens enabling good model to overlap with PCM meta pillars enables high transmission efficiency. The project be experimentally demonstrating an electrically reconfigurable phase-change meta lens capable of modulation an incident light beam into focusing of defocusing two different statures. This work represents a critical advance towards the development of integrable dynamic meta lens and their potential for beamforming applications.

The purpose of this paper is to investigate the impact of advanced immersion lithography process for the development of polarization optics at pixel level on CMOS image sensors. In the first part of this paper, we use Bloch formalism to define regimes that depend on the number of propagative Bloch modes within the structure. The presented analysis gives estimations of required features size to operate in NIR and visible range. The second part of this paper present optical characterization of silicon lamellar grating made on 300 mm wafer using advanced immersion lithography. Characterization results are discussed with respect to optical simulations and reconstructed grating profile is compared to patterning features estimated during first part.

We introduce well-developed optical proximity correction (OPC) techniques to the metasurface-based flat optics manufacturing process. Flat optics, formed by subwavelength scale nanostructure pillar (nanopillar) array, so called metasurface, has become promising substitutes for conventional bulky optical components. For its manufacturing, photolithography is preferable rather than the electron beam lithography (EBL) technique because of its time and cost effectiveness for mass manufacturing. However, the required feature size and pitch of the metasurface for the visible light is approaching the process limit of the ArF immersion lithography. It results in critical dimension (CD) errors due to optical proximity effect and could result in efficiency degradation of the flat optics. In the semiconductor manufacturing industry, OPC based on process modelling and numerical computation has been developed for the last few decades to control the CD on the wafer. Here, a machine learning (ML) model is constructed to avoid the time consumption of the conventional OPC method without losing the accuracy. Various pitches of flat optics metalens, from 465 nm to 160 nm, has been studied for the implementation of the ML OPC. The root mean square (RMS) CD errors < 1 nm and the CD accuracies < 6 nm can be achieved. The CD error percentages over the pillar diameters < 6 % is observed and the improvement of CD error and CD accuracy compared to rule based OPC in small pitches of metalens is demonstrated.

While achromatic focusing with dispersion engineered meta-surfaces has been shown, the time-bandwidth product presents a fundamental trade-off between the diameter, numerical aperture and bandwidth that can be corrected in a single surface for given materials and thickness. We demonstrate design of hybrid systems combining multiple meta-surfaces with refractive lenses. Our method allows to design dispersion engineered systems where each meta-surface adheres to the time-bandwidth limit. As an example achromatic fiber couplers for telecom and imaging the near infra-red spectrum are simulated with the commercial software packages: PlanOpSim and ZEMAX. The wavefront aberration is below λ/12 for all specified wavefronts.

A telephoto lens, which has a long effective focal length to obtain highly magnified images of objects, has been utilized in various imaging systems such as camera modules and astronomical telescopes. Nevertheless, the wasted space between the lens and the image sensor due to the long focal length and the huge volume of refractive lenses pose a major hurdle for system miniaturization. In this work, we propose a novel type of telephoto lens breaking the trade-off between system volume and magnification factor by arranging multiple metasurfaces on a glass substrate in a horizontal direction. This configuration obtains vastly extended optical path length leading to a high magnification factor within a downsized volume.

Multispectral imaging (MSI) provides scenes with multiple narrowband spectral channels. It plays an important role in disciplines such as remote sensing and medical diagnoses. Based on multispectral filter arrays (MSFA), fast and integrated multispectral imaging can be achieved. We demonstrate a wide range multispectral Fabry-Perot (FP) color filter array based on two-dimensional subwavelength gratings and selective suppression. A thin metal layer is added inside the cavity of a FP resonator to selectively suppress the odd-order resonant peaks. The metal layer provides a larger free spectral range and smaller full width at half maximum (FWHM) compared to the conventional FP resonator while maintaining the high transmission. It also reduces the infrared transmission off the reflection range of the distributed Bragg mirror of the FP resonator. With selective suppression, we can exploit the second-order resonant peak by suppressing the odd-order resonant peaks. The smaller reflection phase shift and FWHM of the second-order transmission peak enable a wide range MSFA covering a spectrum from red to NIR (630nm-960nm) with FWHM smaller than 30nm. To be able to tune the resonant peak, we pattern nano-rods with grating or mesh structures in the cavity layers. By manipulating the shape and the size of nano-rods, we can tune the transmission peaks without changing the physical thicknesses of the layers. This has the promise of a monolithic broadband multispectral color filter array and paves the way for one-shot multispectral imaging.

Building visible wavelength metalenses presents significant challenges for nanofabrication due to the high aspect ratio features and tight tolerances required for good performance. The requisite phase profiles often impart dramatic changes in nanostructure fill fraction, which are challenging to pattern via optical lithography. One metasurface of interest is a spatially-varying array of nanopillars ranging in diameter from 70nm - 180nm, with gaps between pillars ranging from 180nm - 70nm. To manufacture this and other metastructured devices in volume, Nanoimprint Lithography (NIL) becomes a key enabling technology due to its demonstrated scalability and ability to reliably replicate nanostructures with extremely tight tolerances, even with variations in local spacing. Another requirement for building metasurfaces for visible light applications, is the ability to pattern full wafers with good repeatability in high volume. Moxtek has therefore set up a 200 mm diameter manufacturing demonstration, where high aspect ratio nanopillars of varying diameter are etched from high refractive index material in order to make visible wavelength metalenses. In this work, metalenses designed for green light were fabricated with both a square grid arrangement and with a radially periodic arrangement. The metalenses were also given a protective coating and the focusing performance was characterized. The manufacturing process evaluation has three key components: 1) characterize the processing bias (from design dimensions to final nanostructure dimensions) at various stages; 2) monitor process stability and repeatability using metrology test devices distributed over the wafer; 3) characterize and verify functioning optical devices. Collectively, we have demonstrated volume manufacturing of metalenses for the visible regime, which was made possible by high precision NIL and Etch processes.

The monitoring of Earth’s atmosphere requires routine measurements of many gasses and aerosols. The most common technique to perform this task is hyperspectral imaging (HSI). However, with the push to integrate HSI sensing capabilities on small platforms, e.g. cubesats and UAVs, the development of smaller, cheaper, higher performing, and low power HSI systems is necessary. Current HSI systems are composed of a large and complex assortment of lenses, filters and cameras that are large, heavy, expensive, and intolerant to physical shocks—all things that make them challenging for use in space-based sensing and imaging applications. The metamaterial filter described in this work eliminates the need for many of the previously necessary optics because it can spectrally filter light independent of the lights angle of incidence—this allows for a focused beam of light to be filtered by the metamaterial. This is in distinct contrast to grating-based HSI systems where the spectrometer requires collimated light. Additionally, the metamaterial filter is designed to filter light only at the desired spectral bands; this is a great benefit for small-platform systems because of the substantially reduced data rate and required computational resources.

During the last decade, active metasurface has attracted significant attention from academia and industry because of its unparalleled advantages over conventional technologies. Active metasurface using electrically controlled liquid crystal (LC) is one of the most promising types of active metasurface towards industrial applications. In this work, we report a silicon metasurface immersed in a nematic liquid crystal for transmission amplitude modulation. Tunable resonance was realized by applying an AC voltage and the resonance was tuned in the spectral range of 1524 nm ~ 1573 nm, which covers the telecommunication C band. The corresponding phase shift at 1555 nm with a maximum value approaching 2π was measured using a Michelson interferometer, which supports the tuning of metasurface resonance by LC. As a result, the maximal modulation depth in transmission amplitude of 94% as experimentally recorded at 1530 nm. In addition, the high quality of LC photoalignment on metasurface was evaluated by examining the transmitted light intensity between crossed polarizers. The response time of sub-milliseconds can be obtained, thanks to the thin cell thickness of only 1 μm. The high alignment quality and fast response time demonstrated in this work shows a promising future for metasurface-integrated liquid crystal on silicon (meta-LCoS) spatial light modulators (SLMs), especially for telecommunication applications.