Edge coupler is a key component of silicon-based optoelectronic chips, which dramatically reduces the coupling loss between fibers and transmission waveguides. Here, we propose an ultralow-loss three-step silicon edge coupler based on a 130 nm CMOS process. By replacing the silicon substrate with a material with a lower refractive index than silicon oxide, the silicon leakage loss and polarization-dependent loss can be significantly improved. This structure avoids the existence of a cantilever, which enhances the mechanical strength of the edge coupler. Coupling with standard single-mode fiber, the simulation results demonstrate that the TE/TM mode has an ultralow loss of 0.63/1.08 dB at 1310 nm and 0.57/1.34 dB at 1550 nm, and the 0.5 dB bandwidth covering the entire communication band is about 400 nm. In the entire communication band, the polarization-dependent loss is less than 0.8 dB. Furthermore, we propose a taper shape design method based on mode analysis, which can be adapted for any taper to improve its compactness. Compared with the parabolic shape, the coupling loss of the edge coupler with a length of 460 μm for the TE mode is improved by 0.3 dB on average, this edge coupler provides a feasible solution for fiber-to-chip coupling and is perfectly suitable for wavelength division multiplexing applications in optical communications.

Inverse design effectively promotes the miniaturization of integrated photonic devices through the modulation of subwavelength structures. Utilizing a theoretical prior based inverse design, we propose an ultra-compact integrated polarizing beam splitter consisting of a standard silicon-on-insulator (SOI) substrate and a tunable air–silicon column two-dimensional code metasurface, with a footprint of 5 × 2.7 μm². The effective refractive index of the waveguide is modulated by adjusting the two-dimensional code morphology in the additional layer to achieve efficient polarization beam splitting. The simulation results demonstrate high performance, with a low insertion loss (10.76 dB) in a bandwidth of 80 nm covering the C-band. The device can withstand manufacturing errors up to ±20 nm and is robust to process defects, such as the outer proximity effect, and thus is suitable for ultra-compact on-chip optical interconnects.

In an azimuth multichannel synthetic aperture radar (SAR) system operating in sliding spotlight mode or Terrain Observation by Progressive Scans (TOPS) mode, due to the varying Doppler centroid and the greater processed Doppler bandwidth, the conventional channel phase error estimation algorithms that tailored to stripmap mode will fail and unable to be directly employed. To address these issues, a deramping-based method is proposed in this letter, which extends the conventional methods to sliding spotlight and TOPS cases. By multiplying the signals of each channel with the corresponding deramp phase, the problem of varying Doppler centroid is solved, and its resulting greater Doppler bandwidth is reduced. Therefore, the spectral properties of the signals are the same as those in the stripmap case, and the conventional channel phase error estimation methods can be applied subsequently. Estimation and imaging results of the simulation data and the real data of GaoFen-3 (GF-3) operating in dual-channel sliding spotlight mode demonstrate the effectiveness of the proposed method.