IntroductionWe present a polarization-coded binary phase mask based on spherical aberration (BPM-SA), which is numerically investigated to extend the depth of focus.MethodsFirst, we generate the baseline binary phase mask by binarizing the fourth-order spherical-aberration phase function into concentric 0- and π-phase zones. To improve axial beam shaping, we introduce polarization coding using Jones retarders in the binary zones, and combine the resulting fields through a linear analyzer.ResultsThe depth of focus (DOF) was evaluated using a 90% axial intensity criterion. Compared with a BPM-SA, the proposed polarization-coded BPM-SA suppresses the central intensity dip caused by destructive interference.DiscussionPolarization coding synthesizes a continuous, uniform axial intensity profile over an extended depth of focus (EDOF) without significantly degrading transverse resolution.
Silicon oxynitride (SiON) is a highly adaptable material platform for photonic integrated circuits owing to its refractive index tunability and full CMOS compatibility. In this work, an integrated surface plasmon resonance (SPR) sensor based on a robust SiON rib waveguide is demonstrated. The sensor geometry and modal properties were optimized using two-dimensional finite element method (FEM) simulations. The sensor performance was evaluated by direct edge coupling within the 550–915 nm spectral range. The influence of the plasmonic layer was first investigated by tracking the resonance dip for gold thicknesses of 20–40 nm with dimethyl sulfoxide (DMSO, n = 1.47) as the analyte. The response was then simulated matching approximately volumetric water-isopropyl alcohol (IPA) mixtures (n = 1.33–1.38), yielding an averaged sensitivity of 158 nm/RIU changing from 80 (water) up to 350 (IPA) nm/RIU that increases with the analyte refractive index. The results confirm that matching the SiON core refractive index to the target analyte enhances the evanescent coupling and thereby the sensitivity. The combination of index tunability, robust architecture, and simple CMOS-compatible fabrication makes the presented platform a versatile candidate for lab-on-a-chip sensing.
Single-shot phase-shifting interferometry (SSPSI) has emerged as a powerful solution for quantitative phase retrieval in situations where conventional multi-step phase-shifting techniques fail due to vibration, motion, or limited acquisition speed. By encoding the required phase diversity within a single interferogram, either spatially or computationally, SSPSI enables real-time and full-field measurement without sacrificing spatial resolution. This paper provides a comprehensive overview of the theoretical foundations, current methodologies, and remaining challenges of SSPSI. The basic principle of interferometric phase extraction is first revisited to establish the transition from classical N-step algorithms to single-frame strategies. Existing approaches are then classified according to the mechanism used to introduce phase shifts, including spatial-carrier encoding and digital or computational techniques such as Hilbert, Riesz, wavelet, and monogenic-signal–based analysis. Each family of methods is examined in terms of phase accuracy, robustness to noise, implementation complexity, and suitability for dynamic measurements. Particular attention is given to recent advances in digital and hybrid techniques that numerically generate π/2-shifted fringe patterns from a single image, enabling precise phase recovery without experimental modulation.
To meet the stringent ultra-reliable connectivity demands of 6G applications such as enhanced broadband and autonomous driving, optical wireless communication (OWC) is considered a key candidate technology. In this work, we investigate the performance of an intelligent reflecting surface (IRS)-aided OWC system by analyzing the signal-to-interference-plus-noise ratio (SINR), data rate, and sum rate through comprehensive MATLAB simulations. The impact of key system parameters on these performance metrics is systematically studied. Furthermore, an analytical expression for the optimal line-of-sight (LoS) channel gain is derived to maximize SINR, data rate, and sum rate. This optimization enables the selection of higher-order M-pulse amplitude modulation (M-PAM) schemes, thereby enhancing channel capacity (CC), spectral efficiency (SE), and energy efficiency (EE) of the IRS-aided OWC system. Simulation results demonstrate that for an SINR of 14.52 dB, 4-PAM is identified as the most suitable advanced digital modulation scheme for reliable data transmission. Additionally, the proposed system achieves a maximum sum rate of 32 Mbps for two mirror arrays and two blockages, which is approximately three times higher than the corresponding results reported in the existing literature. These findings highlight the substantial potential of IRS-assisted OWC systems as an enabling technology for future 6G networks.
