Perfect absorption and polarization conversion of electromagnetic wave (EM) are of significant importance for numerous optical applications. Vanadium dioxide (VO₂), which can be converted from insulating state to metallic state by being exposed to different temperatures, is introduced into a metallic square loop to constitute a switchable bifunctional plasmonic metasurface for perfect absorption and polarization conversion. Combined theoretical analyses and numerical simulations, the results show that at temperature T = 356 K, the metasurface acts as a perfect absorber with nearly 91% absorptance at the wavelength of 1547 nm. When the temperature decreases to T = 292 K, the metasurface expresses as a high efficiency (about 94%) polarization converter with the polarization conversion ratio up to 86% around 1550 nm. The designed bifunctional metasurface has plenty of potential applications such as energy harvesting, optical sensing and imaging. Moreover, it can also provide guidance to research tunable, smart and multifunctional devices.

We propose a novel waveguide design of a polarization-maintaining few mode fiber (PM-FMF) supporting $\ge 10$ non-degenerate modes, utilizing a central circular air hole and a circumjacent elliptical-ring core. The structure endows a new degree of freedom to adjust the birefringence of all the guided modes, including the fundamental polarization mode. Numerical simulations demonstrate that, by optimizing the air hole and elliptical-ring core, a PM-FMF supporting 10 distinctive polarization modes has been achieved, and the effective index difference $\mathrm{\Delta }{n}_{\mathrm{eff}}$ between the adjacent guided modes could be kept larger than $1.32\times {10}^{-4}$ over the whole $\mathrm{C}+\mathrm{L}$ band. The proposed fiber structure can be flexibly tailored to support an even larger number of modes in PM-FMF (14-mode PM-FMF has been demonstrated as an example), which can be readily applicable to a scalable mode division multiplexing system.

Optics InfoBase is the Optical Society's online library for flagship journals, partnered and copublished journals, and recent proceedings from OSA conferences.

We investigate the pulse evolution and energy conservation condition at the temporal boundary under third-order dispersion. When the fundamental soliton crosses the temporal boundary and forms two reflected pulses and one transmitted pulse, the power of the transmitted pulse first increases and then decreases as the incident spectrum shifts toward the blue side. If the transmitted spectrum lies in the anomalous group-velocity dispersion region, second-order soliton is formed and dispersive wave is radiated. We present a modified phase-matching condition to predict the resonance frequencies. The predicted results are in good agreement with the results obtained by numerically solving the nonlinear Schrödinger equation.

Weakly coupled multicore fiber (WC-MCF) is promising for use in short-reach fiber telecommunication systems in the near future. Intercore crosstalk (XT) plays an important role in WCMCF-based short-reach intensity-modulation/direct-detection (IM/DD) systems, because XT can significantly degrade system performance. For the first time, the combined effect of intercore XT and the frequency offset between optical carriers, which is defined as the carrier beating impairment (CBI), is measured and characterized by experiments and numerical simulations. The experimental results show that the CBI causes large fluctuations in the signal-to-noise ratio (SNR) with a normally tolerable XT level. Such SNR fluctuations can additionally reduce the system’s XT tolerance (at worst 1-dB SNR degradation) by as much as 20 dB for 4-level pulse amplitude modulation (PAM-4) transmission. The simulation results show that the CBI is mainly affected by the specific properties of the laser source and the modulation depth of the transmitted signals. These results suggest that the XT should be designed to be much smaller for WCMCF-based short-reach IM/DD systems when there is the CBI.

A hybrid plasmonic waveguide Bragg grating (HPWBG) consisting of a polyvinyl alcohol (PVA) microfiber coupled with metal strips oriented at right angles is reported for simultaneous measurement of humidity and temperature. Due to the convenient adherence of PVA microfiber to metal gratings and its easy connectivity to silica fiber tapers, the hybrid plasmonic waveguide sensor exhibits high flexibility. Numerical calculation reveals that TM polarization shows more prominent Bragg reflection owing to hybrid plasmonic modes exciting. Two hybrid plasmonic TM modes, namely the fundamental mode and the high-order mode, are excited, resulting in two separate reflection peaks. As the two reflection peaks exhibit different behaviors in response to changes in humidity and temperature, simultaneous measurement of humidity and temperature can be realized through a sensitivity coefficient matrix. The experimental results show that the humidity sensitivity reaches −1.98 nm/%RH in the range of 30%–90%RH and the temperature sensitivity is −0.64 nm/°C within a temperature range of 20–90 °C for a PVA microfiber diameter of 1.57 μm. The excellent sensing performance, compactness, and flexibility of the hybrid plasmonic waveguide make it an encouraging choice for humidity and temperature sensing applications.