A liquid-filled D-shaped fiber (DF) cavity serving as an in-fiber Mach–Zehnder interferometer (MZI) has been proposed and experimentally demonstrated for temperature sensing with ultrahigh sensitivity. The miniature MZI is constructed by splicing a segment of DF between two single-mode fibers (SMFs) to form a microcavity (MC) for filling and replacement of various refractive index (RI) liquids. By adjusting the effective RI difference between the DF and MC (the two interference arms), experimental and calculated results indicate that the interference spectra show different degrees of temperature dependence. As the effective RI of the liquid-filled MC approaches that of the DF, temperature sensitivity up to −84.72 nm/°C with a linear correlation coefficient of 0.9953 has been experimentally achieved for a device with the MC length of 456 μm, filled with liquid RI of 1.482. Apart from ultrahigh sensitivity, the proposed MCMZI device possesses additional advantages of its miniature size and simple configuration; these features make it promising and competitive in various temperature sensing applications, such as consumer electronics, biological treatments, and medical diagnosis.

A surface plasmon resonance (SPR) biosensor, which contains an overlayer of titanium dioxide nanoparticles (TDNPs) to modify the plasmonic interface, has been developed and investigated. Owing to its large surface area and high refractive index, the TDNP overlayer significantly enhances the probing electric field intensity and detection sensitivity. This sensitivity is related to the TDNP overlayer thickness, which can be engineered by changing the TiO₂–ethanol dispersion’s spin-coating concentration. The highest refractive index sensitivity for ethylene glycol measurement is 2567.3 nm/RIU, which is 38% higher than that of a conventional SPR sensor with an uncoated gold film. The proposed TDNP-SPR sensor also exhibits a 1.59-fold sensitivity enhancement in fetal bovine serum detection. Moreover, the proposed interface modification approach that is applied without additional biochemical amplification steps is chemical-free and contamination-free; therefore this TDNP-SPR sensor could be integrated into a sensitive, cost-effective, and biocompatible platform for rapid and label-free biochemical detection.

In this work, a new type of self-powered, high-performance ultra-thin p-Si/n-ZnO nanowire (NW) flexible photodetector (PD) and its application as full-spectrum optical sensor and pyroelectric nanogenerator (PENG) are demonstrated. The working mechanism of PDs for PENGs is carefully investigated and systematically analyzed. The self-powered PDs exhibit high responsivity (1200 mA/W), high detectivity (10¹³ Jones) and fast response (τ_r = 18 μs, τ_f = 25 μs) under UV illumination. High and stable short-circuit output currents at each wavelength from ultraviolet (UV) to near-infrared (NIR) demonstrates that the device can realize full-spectrum optical communication. An experiment in which the PENG powers other devices is designed to further demonstrate the proposed working mechanism. This work provides an effective approach to realize self-powered, high-performance PDs for full-spectrum communication. Also, the fabrication of the PENG utilizing a simple and low-cost method shows its potential applications in self-powered flexible electronic devices.