In this work, we realize a large-size single-mode silica-on-silicon (SOS) waveguide from a small-size single-mode silicon-on-insulator (SOI) waveguide at the two ends of the chip by a phosphorous-dopant enhanced complementary etching-oxidation of silicon (CEOS) method to implement a low-loss fiber-chip butt-coupling (FCBC). We model and investigate the geometrical change, and P-dopant caused refractive index change of P:SiO 2 waveguide core with both the numerical calculation and software simulator. As a result, the SOS waveguide not only greatly reduces the FCBC loss but also creates the supersmooth sidewalls of waveguides. With such a CEOS technique, a large-sized single-mode SOS waveguide is fabricated to monolithically integrate with the SOI waveguide via a taper. Consequently, a ∼6 dB IL reduction and a ∼3 dB FCBC loss reduction are achieved, and then FCBC loss lower than 1.2 dB is predicted once the taper structure is optimized by a conformal transportation theory. Hence, this work is an alternative route to fabricating silicon photonic integrated circuit (PIC) chips that possess both the on-chip and FCBC optical losses.

The growing demand for holography and its wide-ranging applications necessitate advancements to make this technology more accessible and adaptable to modern technological requirements. Nematic liquid crystals (NLCs) enable holographic projection by exploiting the geometric phase of light through carefully designed phase patterns. However, NLC-based holography faces challenges, particularly in terms of projection quality and the presence of zero-order leakage—a bright spot that overlaps the reconstructed image. The efficiency of the reconstructed image is strictly related to the thickness of the NLC layer, which is challenging to control with high precision. In this work, we use chiral liquid crystal (CLC) to fabricate reflective holograms. To address the issue of leakage waves overlapping the reconstructed image, we propose an interference-based fabrication approach. This approach combines the phase pattern of the hologram with a diffraction grating by interfering a plane wave with a tailored wavefront precisely matching the hologram’s phase pattern. As a result, the image is reconstructed away from the zero-order reflection, and the leakage overlapping with the reconstructed image is reduced significantly.

This study introduces a high-performance dual-channel surface plasmon resonance (SPR) sensor based on a photonic crystal fiber (PCF) platform, designed to detect analytes with refractive indices (RIs) both lower and higher than that of silica. The proposed configuration integrates two distinct analyte channels to achieve broad detection capability and enhanced structural adaptability. The first channel, positioned externally to the PCF, employs a gold layer to induce SPR excitation, whereas the second channel is embedded within the fiber at the centre. A gold film deposited along the inner wall of a neighboring air hole of the second channel works as a plasmonic medium. This indirect plasmonic configuration effectively eliminates direct contact between the metallic surface and liquid analytes, thereby mitigating oxidation and significantly improving the sensor’s operational stability. The optical performances of the sensor were numerically analyzed and optimized using the finite element method (FEM). Simulation outcomes reveal superior sensing performance, with the external channel exhibiting a maximum wavelength sensitivity (WS) of 16,000 nm/RIU and an amplitude sensitivity (AS) of 5030 RIU −1 , while the internal channel achieves 15,000 nm/RIU and 724 RIU −1 , corresponding to resolutions of 6.25×10 −6 RIU and 6.67×10 −6 RIU, respectively. The proposed sensor demonstrates wide detection ranges of 1.31–1.42 for the external channel and 1.44– 1.52 for the internal channel, enabling precise and reliable identification of analytes across diverse refractive indices. Owing to its wide sensing range, high sensitivity, and oxidation-resistant architecture, this dual-channel SPR sensor presents a promising platform for advanced applications in biochemical diagnostics, food quality control, environmental monitoring, and chemical analysis.