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Polarization-insensitive semiconductor optical amplifiers (SOAs) in all-optical networks can improve the signal-light quality and transmission rate. Herein, to reduce the gain sensitivity to polarization, a multi-quantum-well SOA in the 1550 nm band is designed, simulated, and developed. The active region mainly comprises the quaternary compound InGaAlAs, as differences in the potential barriers and wells of the components cause lattice mismatch. Consequently, a strained quantum well is generated, providing the SOA with gain insensitivity to the polarization state of light. In simulations, the SOA with ridge widths of 4 µm, 5 µm, and 6 µm is investigated. A 3 dB gain bandwidth of >140 nm is achieved with a 4 µm ridge width, whereas a 6 µm ridge width provides more output power and gain. The saturated output power is 150 mW (21.76 dB gain) at an input power of 0 dBm but increases to 233 mW (13.67 dB gain) at an input power of 10 dBm. The polarization sensitivity is <3 dBm at −20 dBm. This design, which achieves low polarization sensitivity, a wide gain bandwidth, and high gain, will be applicable in a wide range of fields following further optimization. [ABSTRACT FROM AUTHOR]

The paper presents a wide-bandwidth, low-polarization semiconductor optical amplifier (SOA) based on strained quantum wells. By enhancing the material gain of quantum wells for TM modes, we have extended the gain bandwidth of the SOA while reducing its polarization sensitivity. Through a combination of tilted waveguide design and cavity surface optical thin film design, we have effectively reduced the cavity surface reflectance of the SOA, thus decreasing device transmission losses and noise figure. At a wavelength of 1550 nm and a drive current of 1.4 A, the output power can reach 188 mW, with a small signal gain of 36.4 dB and a 3 dB gain bandwidth of 128 nm. The linewidth broadening is only 1.032 times. The polarization-dependent gain of the SOA is below 1.4 dB, and the noise figure is below 5.5 dB. The device employs only I-line lithography technology, offering simple fabrication processes and low costs yet delivering outstanding and stable performance. The designed SOA achieves wide gain bandwidth, high gain, low polarization sensitivity, low linewidth broadening, and low noise, promising significant applications in the wide-bandwidth optical communication field across the S + C + L bands. [ABSTRACT FROM AUTHOR]

In order to improve the interior sound quality of Electric Vehicles (EV), solve the problem of low sense of power and comfort of the interior sound as well as the large electromagnetic excitation order noise of motor and the sharp interior sound, this article designs a dynamic active sound control system for EV under accelerated driving conditions. Firstly, by comparing and analyzing the sound spectrum characteristics of fuel vehicle (FV) and EV during acceleration, a short-time Fourier transform (STFT) is adopted to extract and synthesize the engine sound. Secondly, the influence of the engine order composition and the energy distribution in the frequency domain on the sound quality of the vehicle is analyzed, and an active control system for sound quality is proposed. And the software and hardware development of the active control sound system is completed. Finally, through real-vehicle testing and verification, the sense of comfort and power of the EV interior sound has been greatly improved during acceleration, and the total value of interior sound can meet the requirement. The sound pressure level and loudness of interior sound have been increased, and the sharpness of the sound inside the vehicle has been improved, with a maximum reduction of 1.0acum. [ABSTRACT FROM AUTHOR]

The micro‐ring resonator (MRR) is a crucial element in integrated photonics. It allows for the realization of various optical devices, including integrated filters, modulators, micro‐ring laser cavities, detectors, optical logic switches, and nonlinear optical devices. The development of integrated photonics has enabled the integration of these devices with other components into a photonic chip to perform specific functions. For instance, widely tunable MRR‐based lasers have been integrated with optical phased arrays (OPAs), detectors, and other elements to form a fully integrated LiDAR engine. Advances in nanofabrication have facilitated the miniaturization of nanophotonic phased arrays and on‐chip lasers. MRR‐based integrated external cavity lasers (ECLs) and integrated optical frequency combs (OFCs) have significantly enhanced the scanning and detection capabilities of LiDAR recently. Additionally, their size and power consumption have been continuously reduced, rendering them suitable for chip‐scale integration. This paper systematically reviews the major advancements of MRR‐based integrated lasers for chip‐scale LiDAR. [ABSTRACT FROM AUTHOR]

Background: With the increasing survival rate of smaller newborns and twins, previous growth curves may not accurately assess the growth of extremely preterm infants (EPIs). Our study aimed to establish birth weight percentile curves for singletons and twins in EPIs from China and the USA and compare the differences between them., Methods: In China, EPIs were from 31 provinces, from 2010 to 2021. The collected information was sex, gestational age, birth weight, singletons and twins. We used the generalised additive models for location scale and shape method to construct the birth weight percentile curves by gestational age and sex for EPIs. The National Vital Statistics System database from 2016 to 2021 was also analysed. We compared the differences between the 50th birth weight percentile curves of the two databases., Results: We identified 8768 neonates in China (5536 singletons and 3232 twins) and 121 933 neonates in the USA (97 329 singletons and 24 604 twins). We established the 3rd, 10th, 25th, 50th, 75th, 90th and 97th birth weight reference curves for China and the USA. The results showed that males had higher birth weights than females. In China, for the same gestational age and sex, birth weights in singletons and twins were found to be similar, though singleton males born in China had slightly higher birth weights than male twins. In the USA, birth weights were also similar for females and males, with the same gestational age in singletons and twins., Conclusion: We established birth weight reference percentile curves by gestational age and sex for singletons and twins among EPIs in China and the USA., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)