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1. Quadratic extension to retrace error calibration algorithm for non-null interferometric surface figure testing of nominally flat reflective surfaces

   https://doi.org/10.1364/FREEFORM.2019.JW3A.7  

   Tangari Larrategui, M; Yanqi, Z; Rocha, A.D.; Brown, T.G.; Ellis, J.D. (April 2019, Design and Fabrication Congress 2019 (Freeform, OFT) © OSA 2019)

   We present a slope dependent calibration algorithm for interferometric surface figure testing. RMS wavefront error is reduced 40.7% (10.8% for linear method) from the uncalibrated measurement for a R/22.7 mirror tested against a flat reference. © 2019 The Author(s) OCIS codes: 110.0110 Imaging systems; 120.0120 Instrumentation, measurement, and metrology 

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2. Design and performance of the ALPS II regeneration cavity

   https://doi.org/10.1364/OE.540297  

   Kozlowski, Todd; Wei, Li-Wei; Spector, Aaron_D; Hallal, Ayman; Frädrich, Henry; Brotherton, Daniel_C; Oceano, Isabella; Ejlli, Aldo; Grote, Hartmut; Hollis, Harold; et al (March 2025, Optics Express)

   The regeneration cavity (RC) is a critical component of the Any Light Particle Search II (ALPS II) experiment. It increases the signal from possible axions and axion-like particles in the experiment by nearly four orders of magnitude. The total round-trip optical losses of the power circulating in the cavity must be minimized in order to maximize the resonant enhancement of the cavity, which is an important figure of merit for ALPS II. Lower optical losses also increase the cavity storage time, and with the 123 meter long ALPS II RC we have demonstrated the longest storage time of a two-mirror optical cavity. We measured a storage time of 7.17±0.01ms, equivalent to a linewidth of 44.4 Hz and a finesse of 27,500 at a wavelength of 1064 nm. 

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3. Proof of the elliptic expansion moonshine conjecture of Căldăraru, He, and Huang

   https://doi.org/10.1090/proc/16032  

   Hong, Letong; Mertens, Michael; Ono, Ken; Zhang, Shengtong (January 2022, Proceedings of the American Mathematical Society)

   Using predictions in mirror symmetry, Căldăraru, He, and Huang recently formulated a “Moonshine Conjecture at Landau-Ginzburg points” [arXiv:2107.12405, 2021] for Klein’s modular j j -function at j = 0 j=0 and j = 1728. j=1728. The conjecture asserts that the j j -function, when specialized at specific flat coordinates on the moduli spaces of versal deformations of the corresponding CM elliptic curves, yields simple rational functions. We prove this conjecture, and show that these rational functions arise from classical 2 F 1 _2F_1 -hypergeometric inversion formulae for the j j -function. 

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4. Strategies to reduce the thermoelastic loss of multimaterial coated finite substrates

   https://doi.org/10.1088/1361-6382/acdd49  

   Zhou, R; Molina-Ruiz, M; Hellman, F (June 2023, Classical and Quantum Gravity)

   Abstract Thermoelastic loss is an important energy dissipation mechanisms in resonant systems. A careful analysis of the thermoelastic loss is critical to the design of low-noise devices for high-precision applications, such as the mirrors used for gravitational-wave (GW) detectors. In this paper, we present analytical solutions to the thermoelastic loss due to thermoelasticity between different materials that are in contact. We find expressions for the thermoelastic loss of multimaterial coatings of finite substrates, and analyze its dependencies on material properties, mirror design and operating experimental conditions. Our results show that lower operating mirror temperature, thinner layers and higher number of interfaces in the coating, and the choice of the first layer of the coating that minimizes the thermal expansion mismatch with the substrate are strategies that reduce the thermoelastic loss and, therefore, diminish the thermal noise that limits the resolution in sensing applications. The results presented in this paper are relevant for the development of low-noise GW detectors and for other experiments sensitive to energy dissipation mechanisms when different materials are in contact. 

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5. A 27.5–46.2-GHz Broadband Low Noise Amplifier With IP3 Enhancement

   https://doi.org/10.1109/LMWT.2023.3283943  

   Hu, Y.; Chi, T. (June 2023, IEEE Microwave and Wireless Technology Letters)

   This letter presents a 27.5–46.2-GHz broadband low-noise amplifier (LNA) featuring IP3 enhancement. The LNA bandwidth (BW) is extended by implementing dual-resonant input matching and a broadband output network. The LNA IP3 is enhanced by incorporating parallel PMOS and NMOS paths in the second stage, with their output currents combined through a three-winding transformer. Implemented using the GlobalFoundries 45-nm CMOS silicon-on insulator (SOI) process, the LNA demonstrates 27.5–46.2 GHz effective BW, 2.1 dB minimum noise figure (NF), and 19.8 dB peak gain. The measured IIP3 is − 3.6 dBm at 34 GHz under 25.5 mW DC power consumption. Compared to recently reported broadband LNAs with a similar frequency range, this design achieves the state-of-the-art NF, IIP3, and figure-of-merit (FoM). 

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