Actively-controlled second harmonic generation in a silicon nitride ring resonator is proposed and simulated. The ring was designed to resonate at both pump and second harmonic wavelengths and quasi-phase-matched frequency conversion is induced by a periodic static electric field generated by voltage applied to electrodes arranged along the ring. Nonlinear propagation simulations were undertaken and an efficiency of -21.67 dB was calculated for 60 mW of pump power at 1550 nm and for a 30V applied voltage, which compares favorably with demonstrated all-optical second harmonic generation in integrated microresonators. Transient effects were also evaluated. The proposed design can be exploited for the construction of electro-optical devices based on nonlinear effects in CMOS compatible circuits.
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http://dx.doi.org/10.1364/OE.21.032690 | DOI Listing |
J Matern Fetal Neonatal Med
December 2025
Department of Cardiac Surgery, Lanzhou University Second Hospital, Lanzhou University, Lanzhou, China.
Objective: There is an increase in the application data of Extracorporeal Membrane Oxygenation (ECMO) in perinatal women, particularly since the outbreak of coronavirus disease 2019. Therefore, we reviewed publications on the use of ECMO in pregnant and postpartum women and analyzed the maternal and fetal outcomes, updated the progress of ECMO in perinatal women.
Methods: We conducted a systematic literature search across PubMed, EMBASE, Cochrane Library, and the International Clinical Trials Registry (ICTRP), yielding 30 eligible clinical studies that investigated the application of ECMO during pregnancy.
In this paper, we demonstrate a high-contrast front-end laser system based on Yb: YAG solid-state laser for Ti: sapphire terminal amplification. An ultrafast Yb: YAG solid-state laser is used to generate a broad-spectrum seed through white light generation (WLG), and then the signal light near 1600 nm is amplified by three-level colinear optical parametric chirped pulse amplification (OPCPA). Finally, a fs second harmonic generation (SHG) is used to obtain a laser output with a central wavelength of 795 nm, a pulse width of 40.
View Article and Find Full Text PDFNonlinear emission phenomena observed in transition metal dichalcogenides (TMDCs) have significantly advanced the development of robust nonlinear optical sources within two-dimensional materials. However, the intrinsic emission characteristics of TMDCs are inherently dependent on the specific material, which constrains their tunability for practical applications. In this study, we propose a strategy for the selective enhancement and modification of second-harmonic generation (SHG) emission in a multilayer WS flake through the implementation of a silicon (Si)-based circular Bragg grating (CBG) structure positioned on an Au/SiO substrate.
View Article and Find Full Text PDFThis paper demonstrates a customized quartz tuning fork (QTF) coated with the titanium carbide (TiCT) MXene film that can effectively enhance the sensitivity of light-induced thermoelastic spectroscopy (LITES). The MXene film is coated at the root of the customized QTF. The film area is proven to have little impact on resonance frequency, bandwidth, quality factor, and amplitude of the second harmonic signal (2) based on the fundamental flexural mode.
View Article and Find Full Text PDFMed Phys
January 2025
Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China.
Background: High-resolution brain imaging is crucial in clinical diagnosis and neuroscience, with ultra-high field strength MRI systems ( ) offering significant advantages for imaging neuronal microstructures. However, achieving magnetic field homogeneity is challenging due to engineering faults during the installation of superconducting strip windings and the primary magnet.
Purpose: This study aims to design and optimize active superconducting shim coils for a 7 T animal MRI system, focusing on the impact of safety margin, size, and adjustability of the second-order shim coils on the MRI system's optimization.
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