To overcome the weak intrinsic birefringence and limited polarization-splitting capability of conventional buried silica waveguides, we propose and fabricate a polarization beam splitter (PBS) based on a Mach–Zehnder interferometer and enabled by stress-induced birefringence on a silica planar lightwave circuit (PLC) platform. The device consists of two 3-dB directional couplers, a reference arm, and a stress-modulation arm. Stress-control trenches are etched on both sides of the modulation arm to break the stress symmetry in the waveguide core, thereby inducing different phase accumulations for the transverse-electric (TE) and transverse-magnetic (TM) modes and routing them to separate output ports. The stress-control trenches are optimized using the finite-element method, while the directional couplers and the complete PBS are optimized using the beam propagation method. Experimental results show that, over the C band, the insertion losses of the target TE and TM channels are below 0.91 and 1.55 dB, respectively. Within the wavelength range of 1545–1560 nm, the polarization extinction ratios of the two channels are higher than 20 and 25 dB, respectively. These results demonstrate that the proposed structure enables on-chip polarization splitting compatible with standard silica PLC fabrication while preserving the low-loss characteristics of the platform.
Inter-core crosstalk remains a major obstacle for dense few-mode multicore fibers, particularly for weakly confined higher-order modes. To address this issue, a ring-trench-assisted elliptical-core six-core five-LP-mode fiber (RT-EC-FM-MCF) is proposed, in which an elliptical core, an inner ring, and an outer trench are synergistically incorporated to suppress inter-core crosstalk through phase mismatch, boundary-induced field blocking, and lateral confinement. Analyses based on the finite-element method and coupled-power theory show that, at a bending radius of 140 mm, the inter-core crosstalk of all five LP modes remains below −40 dB/km, the effective refractive-index difference between adjacent modes exceeds 1 × 10−3, and the effective mode area is greater than 70 μm2. In a 1 km component comparison, the calculated accumulated ICXT of LP21Y is approximately 49 dB lower than that of the trench-only structure. Across 1.33–1.57 μm, the maximum differential mode delay remains below 15 ps/m. These results demonstrate the potential of the proposed architecture for low-crosstalk, high-spatial-density few-mode multicore fibers.
Space-based gravitational-wave detection encodes minute interspacecraft optical path-length variations in laser heterodyne phase for precision phasemeter readout. Besides the main beat note carrying the science measurement, a phasemeter receives clock sidebands, pseudo-random-noise modulation for ranging and communication, and a pilot tone for sampling-jitter correction. Nonlinearity in the analog front end and analog-to-digital converter (ADC) generates harmonic and intermodulation products. High-frequency nonlinear components that remain observable after the analog front end can alias near functional tones after sampling and affect phase readout. We present an algorithm for separability assessment and selective suppression of these spurious tones. It predicts candidates from multitone nonlinear combinations, calculates aliased frequencies, and traces their origins. Guard bands around the functional tones distinguish separable spurs, which undergo selective band-stop processing during operation, from inseparable conflicts used for pre-deployment frequency-plan screening. In numerical simulations, selective suppression reduced the total target-spur energy by 37.95–40.19 dB and improved the spurious-free dynamic range (SFDR) by 24.47–28.03 dB, while introducing a root-mean-square (RMS) difference of 1.125–1.928μrad in the main-beat science phase. Processing the target set identified in ADC data acquired from a phasemeter test platform achieved 38.21 dB of total target-spur energy suppression and improved the SFDR by 12.63 dB, with a processing-induced main-beat-note phase-difference RMS of 3.147μrad. The method therefore suppresses separable spurious tones while identifying inseparable frequency conflicts for pre-deployment screening and excluding them from operational filter targets.
This study aims to determine how rotation affects the coupled temperature, excess carrier density, displacement, and stress distributions in a semiconductor half-space subjected to laser-induced surface heating when density-gradient quantum corrections to carrier transport are included. The model extends classical formulations by incorporating quantum carrier diffusion through a density-gradient approach, along with rotational effects represented by Coriolis and centrifugal forces. The resulting coupled system captures the interaction between elastic deformation, thermal transport, and photo-generated carrier dynamics in a rotating reference frame. Normal-mode analysis is employed to derive the dispersion relations governing wave propagation. Numerical simulations, using silicon as a representative material, investigate how angular velocity affects temperature, displacement, carrier density, and stress distributions. The results demonstrate that rotation significantly modifies transport characteristics, leading to phase shifts, amplitude reduction, and enhanced attenuation of the coupled fields. Furthermore, the combined influence of quantum diffusion and rotation produces smoother spatial distributions and increases thermal penetration depth compared with the non-rotating case. These findings indicate that neglecting rotational effects may lead to inaccurate predictions in high-frequency and micro-scale applications and provide useful insights for advanced optoelectronic and nanoelectromechanical system design.
