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1. DNN Beamforming for High Contrast Targets in the Presence of Reverberation Clutter

   https://doi.org/10.1109/ULTSYM.2019.8925715  

   Luchies, Adam; Byram, Brett (October 2019, 2019 IEEE International Ultrasonics Symposium (IUS))

   We evaluated training deep neural network (DNN) beamformers for the task of high contrast imaging in the presence of reverberation clutter. Training data was generated using simulated hypoechoic cysts and a pseudo nonlinear method for generating reverberation clutter. Performance was compared to standard delay-and-sum (DAS) beamforming on simulated hypoechoic cysts having a different size. For a hypoechoic cyst in the presence of reverberation clutter, when the intrinsic contrast ratio (CR) was -10 dB and -20 dB, the measured CR for DAS beamforming was -9.2±0.8 dB and -14.3±0.5 dB, respectively, and the measured CR for DNNs was -10.7±1.4 dB and -20.0±1.0 dB, respectively. For a hypoechoic cyst with -20 dB intrinsic CR, the contrast-to-noise ratio (CNR) was 3.4±0.3 dB and 4.3±0.3 dB for DAS and DNN beamforming, respectively. These results show that DNN beamforming was able to extend contrast ratio dynamic range (CRDR) by about 10 dB while also improving CNR. 

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2. Efficient, narrow profile waveguide crossings based on rapid adiabatic coupling

   https://doi.org/10.1364/CLEO_SI.2020.SM4J.4  

   Fargas Cabanillas, Josep M.; Zhang, Bohan; Popović, Miloš A. (May 2020, Proceedings of Conference on Lasers & Electro-Optics (CLEO))

   We demonstrate an efficient silicon waveguide crossing based on the rapid adiabatic coupling (RAC) concept. Insertion loss and crosstalk are under 0.05 dB and -50 dB in simulation and under 0.3 dB and -17 dB in experiment across a 100 nm bandwidth. 

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3. A <5 dB NF, > 17 dBm OP _{1 dB} F-Band GaN-on-SiC HEMT LNA with a Monolithic Substrate-Integrated Waveguide Filter

   https://doi.org/10.1109/IMS40175.2024.10600353  

   Thome, Fabian; Schwantuschke, Dirk; Brückner, Peter; Wang, Xiaopeng; Hwang, James_C M; Quay, Rüdiger (June 2024, IEEE)

   This paper demonstrates the monolithic integration of a substrate-integrated waveguide bandpass filter (BPF) and a low-noise amplifier (LNA) at F-band, fabricated in a 70-nm GaN-on-SiC technology. The three-stage LNA alone achieves a state-of-the-art average noise figure of 3.6 dB over 87–115 GHz. The LNA + BPF exhibits a peak gain of 13.6 dB over a 3 dB bandwidth of 17 GHz from 104 to 121 GHz. The average noise figure is 4.9 dB over 87–115 GHz. The OP1 dB and saturated output power are 17.6dBm and >20 dBm, respectively. 

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4. Low Loss Chip-to-Chip Couplers for High Density Co-Packaged Optics

   https://doi.org/10.1364/opticaopen.25852735.v1  

   Weninger, Drew; Otálvaro, Samuel Serna; Ranno, Luigi; Kimerling, Lionel; Agarwal, Anuradha (May 2024, Optica Open)

   An experimentally demonstrated, vertical chip-to-chip evanescent coupler between silicon nitride (Si₃N₄) and silicon (Si) is presented with the coupler loss measured to be 0.39 ± 1.06 dB at 1550 nm with a 1-dB bandwidth of 160 nm extending across the C-band, S-band, and L-band (1480-1640 nm). The average coupling loss was determined to be 0.73 dB for the 1480-1640 nm wavelength range with a ± 2σ tolerance of ± 0.92 dB. The 1-dB lateral alignment tolerance was 1.56 ± 0.14 μm at 1550 nm and the average tolerance was 1.38 ± 0.24 μm across the 1480-1640 nm wavelength regime. In addition, the average coupling loss varied by less than ± 0.35 dB and the average 1-dB alignment tolerance varied by less than ± 30 nm for temperatures varying from 23-60°C. Finally, the average coupling loss range was less than 1.5 dB range across four sets of identically packaged die. This is the first experimental demonstration of an inter-chip, passively assembled evanescent coupler using standard CMOS foundry processes for directly coupling between Si and Si₃N₄, overcoming a waveguide refractive index difference of Δn = 1.32 without requiring taper tip widths of less than 100 nm. 

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5. Multi-layer inverse design of vertical grating couplers for high-density, commercial foundry interconnects

   https://doi.org/10.1364/OE.466015  

   Hammond, Alec_M; Slaby, Joel_B; Probst, Michael_J; Ralph, Stephen_E (August 2022, Optics Express)

   Density-based topology optimization is used to design large-scale, multi-layer grating couplers that comply with commercial foundry fabrication constraints while simultaneously providing beam profiles that efficiently couple to a single-mode optical fiber without additional optics. Specifically, we describe the design process and experimentally demonstrate both single- and dual-polarization grating couplers that couple at normal incidence (0° from the normal) with low backreflections (-13.7 dB and -15.4 dB at the center wavelength), broad 3 dB bandwidths (75 nm and 89 nm), and standard coupling efficiencies (-4.7 dB and -7.0 dB). The dual-polarization grating couplers exhibit over 30 dB of polarization extinction across the entire band. The devices were fabricated on the GlobalFoundries 45CLO CMOS platform and characterized across three separate wafers. This new design approach produces distinct features for multiple foundry layers and yields emitters with arbitrary, user-specified far-field profiles. 

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