About

Samuel K. Roberts is a doctoral student in the Department of History at Columbia University, with a research focus on Modern Europe. His academic advisor is Saada. Roberts is actively engaged in historical research related to Modern European history, contributing to the department's diverse scholarly community. His work is part of Columbia's broader commitment to fostering historical scholarship and academic excellence in the field of European history.

Research topics

• Computer Science
• Optoelectronics
• Engineering
• Materials science
• Electronic engineering
• Electrical engineering
• Optics
• Physics
• Nanotechnology

Selected publications

• Ultra‐Low‐Loss Silicon Nitride Photonics Based on Deposited Films Compatible with Foundries

  Laser & Photonics Review · 2023-01-02 · 56 citations

  articleOpen access

  Abstract The fabrication processes of silicon nitride (Si 3 N 4 ) photonic devices used in foundries require low temperature deposition, which typically leads to high propagation losses. Here, it is shown that propagation loss as low as 0.42 dB cm −1 can be achieved using foundry compatible processes by solely reducing waveguide surface roughness. By postprocessing the fabricated devices using rapid thermal anneal (RTA) and furnace anneal, propagation losses down to 0.28 dB cm −1 and 0.06 dB cm −1 , respectively, are achieved. These low losses are comparable to the conventional devices using high temperature, high‐stress LPCVD films. The dispersion of the devices is also tuned, and it is proved that these devices can be used for linear and nonlinear applications. Low threshold parametric oscillation, broadband frequency combs, and narrow‐linewidth laser are demonstrated. This work demonstrates the feasibility of scalable photonic systems based on foundries.

  PublisherOA PDFDOI

• Measurements and Modeling of Atomic‐Scale Sidewall Roughness and Losses in Integrated Photonic Devices

  Advanced Optical Materials · 2022-06-25 · 35 citations

  articleOpen access1st authorCorresponding

  Abstract Atomic‐level imperfections play an increasingly critical role in nanophotonic device performance. However, it remains challenging to accurately characterize the sidewall roughness with sub‐nanometer resolution and directly correlate this roughness with device performance. A method that allows to measure the sidewall roughness of waveguides made of any material (including dielectrics) using the high resolution of atomic force microscopy is developed. This method is illustrated by measuring state‐of‐the‐art photonic devices made of silicon nitride. The roughness of devices fabricated using both deep ultraviolet (DUV) photo‐lithography and electron‐beam lithography for two different etch processes is compared. To correlate roughness with device performance, a new Payne–Lacey Bending model is described, which adds a correction factor to the widely used Payne–Lacey model so that losses in resonators and waveguides with bends can be accurately predicted given the sidewall roughness, waveguide width and bending radii. Having a better way to measure roughness and use it to predict device performance can allow researchers and engineers to optimize fabrication for state‐of‐the‐art photonics using many materials.

  PublisherOA PDFDOI

• Fabrication-Robust Silicon Photonic Devices in Standard Sub-Micron Silicon-on-Insulator Processes

  arXiv (Cornell University) · 2022-05-23 · 2 citations

  preprintOpen access

  Perturbations to the effective refractive index from nanometer-scale fabrication variations in waveguide geometry plague high index-contrast photonic platforms including the ubiquitous sub-micron silicon-on-insulator (SOI) process. Such variations are particularly troublesome for phase-sensitive devices such as interferometers and resonators, which exhibit drastic changes in performance as a result of these fabrication-induced phase errors. In this Letter, we propose and experimentally demonstrate a design methodology for dramatically reducing device sensitivity to silicon width variations. We apply this methodology to a highly phase-sensitive device, the ring-assisted Mach Zehnder interferometer (RAMZI), and show comparable performance and footprint to state-of-the-art devices while substantially reducing stochastic phase errors from etch variations. This decrease in sensitivity is directly realized as energy savings by significantly lowering the required corrective thermal tuning power, providing a promising path towards ultra-energy-efficient large-scale silicon photonic circuits.

  PublisherOA PDFDOI

• Fabrication-robust silicon photonic devices in standard sub-micron silicon-on-insulator processes

  Optics Letters · 2022-12-12 · 26 citations

  articleOpen access

  Perturbations to the effective refractive index from nanometer-scale fabrication variations in waveguide geometry plague high index-contrast photonic platforms; this includes the ubiquitous sub-micron silicon-on-insulator (SOI) process. Such variations are particularly troublesome for phase-sensitive devices, such as interferometers and resonators, which exhibit drastic changes in performance as a result of these fabrication-induced phase errors. In this Letter, we propose and experimentally demonstrate a design methodology for dramatically reducing device sensitivity to silicon width variations. We apply this methodology to a highly phase-sensitive device, the ring-assisted Mach-Zehnder interferometer (RAMZI), and show comparable performance and footprint to state-of-the-art devices, while substantially reducing stochastic phase errors from etch variations. This decrease in sensitivity is directly realized as energy savings by significantly reducing the required corrective thermal tuning power, providing a promising path toward ultra-energy-efficient large-scale silicon photonic circuits.

  PublisherOA PDFDOI

• Fabrication-Robust Silicon Photonics Platform in Standard 220 nm Silicon Processes

  2021-12-01 · 5 citations

  article

  We present a fabrication-robust silicon photonics platform compatible with standard 220 nm silicon thickness. Our generalized design methodology shows a 4× energy reduction over standard filter designs and was validated in a 300 mm foundry process, showing a promising avenue for reducing thermal tuning energy.

  PublisherDOI

• Methods to achieve ultra-high quality factor silicon nitride resonators

  APL Photonics · 2021 · 167 citations

  • Materials science
  • Optoelectronics
  • Electronic engineering

  On-chip resonators are promising candidates for applications in a wide range of integrated photonic fields, such as communications, spectroscopy, biosensing, and optical filters, due to their compact size, wavelength selectivity, tunability, and flexible structure. The high quality (Q) factor is a main positive attribute of on-chip resonators that makes it possible for them to provide high sensitivity, narrow bandpass, and low power consumption. In this Tutorial, we discuss methods to achieve ultra-high Q factor on-chip resonators on a silicon nitride (Si3N4) platform. We outline the microfabrication processes, including detailed descriptions and recipes for steps such as deposition, lithography, etch, cladding, and etch facet, and then describe the measurement of the Q factor and methods to improve it. We also discuss how to extract the basic loss limit and determine the contribution of each loss source in the waveguide and resonator. We present a modified model for calculating scattering losses, which successfully relates the measured roughness of the waveguide interface to the overall performance of the device. We conclude with a summary of work done to date with low pressure chemical vapor deposition Si3N4 resonator devices, confinement, cross-sectional dimensions, bend radius, Q factor, and propagation loss.

  PublisherOA PDFDOI

• Integrated near-field thermo-photovoltaics for heat recycling

  Nature Communications · 2020 · 126 citations

  • Computer Science
  • Materials science
  • Optoelectronics

  ) and relies on scalable silicon-based process technologies.

  PublisherOA PDFDOI

• Supplementary document for Large-scale optical phased array using a low power multi-pass silicon photonic platform - 4310889.pdf

  Figshare · 2019-01-01

  articleOpen access

  Device design, simulation, measurements and fabrication

  OA PDFDOI

• Scalable low-power silicon photonic platform for all-solid-state beam steering

  2019-05-13 · 3 citations

  article

  Solid-state beam steering is the key to realize miniature, mass-producible LIDAR (Light Detection And Ranging) and freespace communication systems without using any moving parts. The huge power consumption required in solid-state beam steering, however, prevents this technology from further scaling. Here we show two different approaches to enable lowpower solid-state beam steering. In the first approach, we use spatial-mode multiplexing to reduce the power consumption of the phase shifters in a large-scale optical phased array. We show an improvement of phase shifter power consumption by nearly 9 times, without sacrificing optical bandwidth or operation speed. Using this approach, we demonstrate 2D beam steering with a silicon photonic phased array containing 512 actively controlled elements. This phased array consumes only 1.9 W of power while steering over a 70° × 6° field of view. This power consumption is at least an order of magnitude lower compared to other demonstrated large-scale active phased arrays. In the second approach, we achieve 2D beam steering with a switchable emitter array and a metalens that collimates the emitted light. The power consumption of this approach scales logarithmically with the number of emitters and therefore favors large-scale systems. This approach allows straightforward feedback control and better robustness to environmental temperature change. Our approaches demonstrate a path forward to build truly scalable beam steering devices.

  PublisherDOI

• High Quality Factor PECVD Si3N4 Ring Resonators Compatible with CMOS Process

  Conference on Lasers and Electro-Optics · 2019-01-01 · 6 citations

  article

  We demonstrate high-confinement Si3N4 resonators with intrinsic quality factor more than 1 million using standard PECVD process. We show that by addressing scattering, the loss at 1.6 μm can be as low as 0.4 dB/cm.

  PublisherDOI

Frequent coauthors

• Michal Lipson

  27 shared

• Xingchen Ji

  24 shared

• Aseema Mohanty

  16 shared

• You-Chia Chang

  National Yang Ming Chiao Tung University

  13 shared

• Christopher T. Phare

  Columbia University

  11 shared

• Brian Stern

  Nokia (United States)

  11 shared

• Moshe Zadka

  Columbia University

  10 shared

• Steven A. Miller

  9 shared

Education

• Ph.D.

  Princeton University

  2001

• M.A.

  Princeton University

  1997

• B.A.

  University of Virginia

  1995