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1. Low-Loss High-Density Inverse-Designed Structures for High Power Signal Routing on Integrated Silicon Photonics Foundry Platforms

   https://doi.org/10.1364/CLEO_SI.2023.STh4G.4  

   Slaby, Joel B.; Hammond, Alec M.; Ralph, Stephen E. (January 2023, Optica Publishing Group)

   We present inverse-designed compact multi-mode structures (bend, mode converter, and taper) for single-mode operation to enable low-loss, high power, and high-density signal routing with a demonstrated bend insertion loss of 0.48 dB on commercial foundry platforms. 

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2. Methods to achieve ultra-high quality factor silicon nitride resonators

   https://doi.org/10.1063/5.0057881  

   Ji, Xingchen; Roberts, Samantha; Corato-Zanarella, Mateus; Lipson, Michal (July 2021, APL Photonics)

   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. 

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3. Large-range high-speed dynamic-mode atomic force microscope imaging: adaptive tapping towards minimal force

   https://doi.org/10.1088/1361-6528/acd700  

   Chen, Jiarong; Zou, Qingze (May 2023, Nanotechnology)

   Abstract This paper presents a software-hardware integrated approach to high-speed large-range dynamic mode imaging of atomic force microscope (AFM). High speed AFM imaging is needed to interrogate dynamic processes at nanoscale such as cellular interactions and polymer crystallization process. High-speed dynamic-modes such as tapping-mode AFM imaging is challenging as the probe tapping motion is sensitive to the highly nonlinear probe-sample interaction during the imaging process. The existing hardware-based approach via bandwidth enlargement, however, results in a substantially reduction of imaging area that can be covered. Contrarily, control (algorithm)-based approach, for example, the recently developed adaptive multiloop mode (AMLM) technique, has demonstrated its efficacy in increasing the tapping-mode imaging speed without loss of imaging size. Further improvement, however, has been limited by the hardware bandwidth and online signal processing speed and computation complexity.Thus, in this paper, the AMLM technique is further enhanced to optimize the probe tapping regulation and integrated with a field programmable gate array (FPGA) platform to further increase the imaging speed without loss of imaging quality and range. Experimental implementation of the proposed approach demonstrates that the high-quality imaging can be achieved at a high-speed scanning rate of 100 Hz and higher, and over a large imaging area of over 20 µm. 

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4. Unidirectional Light Generation in PT-symmetric Microring Lasers

   https://doi.org/10.1364/CLEO_QELS.2018.FM4E.3  

   Ren, Jinhan; Parto, Midya; Wittek, Steffen; Hokmabadi, Mohammad P.; Christodoulides, Demetrios N.; Khajavikhan, Mercedeh (July 2018, CLEO: QELS_Fundamental Science 2018)

   At resonance, mircoring resonators tend to support two counter-propagating degenerate modes. By incorporating S-bend chiral elements in each resonator, unidirectional single mode lasing below and above PT-symmetry breaking point is experimentally demonstrated. 

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5. Stretchable Optical Waveguide Sensor Suitability for Wrinkle Degree Detection in Soft Robots

   https://doi.org/10.1109/RoboSoft55895.2023.10122087  

   Williamson, J. Garrett; Schultz, Joshua (April 2023, IEEE)

   Optical waveguide deformation sensors are created for less than 15 US Dollars each and evaluated for their usefulness in detecting the severity of wrinkles in a thin-walled soft robot. This severity is quantified by the bend angle produced in the robot. The sensors are integrated into the skin of the robot and tests are performed to determine their usefulness. The sensors prove to be able to accurately track the bend angle of the robotic arm as a wrinkle is induced in a sudden load drop test, a sudden pressure loss test, an incremented load test, and an incremented pressure test. The drop test, specifically, tracked bend angle through many rapid undulations. 

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