We propose a dual-band near-infrared absorber based on the simultaneous excitation of borophene localized surface plasmons (LSPs) and Tamm plasmon polaritons (TPPs). By leveraging the ultrahigh intrinsic carrier density of borophene, this hybrid architecture effectively overcomes the mid-infrared spectral limitations of conventional two-dimensional materials, achieving near-perfect peak absorptances of 98.1% and 97.2%. Theoretical and numerical investigations reveal that the in-plane LSP mode and the longitudinally distributed TPP mode exhibit a highly decoupled nature. The LSP resonance can be actively and independently modulated via the borophene ribbon geometry and electron density, whereas the TPP mode is strictly governed by the underlying one-dimensional photonic crystal and incident angle. Combined with a robust polarization-selective response, this structurally simple yet highly tunable platform offers a versatile physical paradigm for designing next-generation active optical modulators and polarization-sensitive nanophotonic devices.

Surface-enhanced Raman scattering (SERS) enables specific detection of chemical and biological analytes by detecting Raman signals from the molecular bonds in the analytes. Conventionally, rigid substrates have been explored due to their compatibility with semiconductor fabrication technology. Flexible and conformal SERS substrates have a broader scope for real-life applications due to their conformity over any complex surface for effectively sensing target molecules. We employ glancing angle deposition (GLAD) to directly grow silver nanowires (AgNWs) on a textile fabric to obtain flexible and conformal SERS substrates. Glancing angle deposition of AgNWs directly on textile fabrics is an easy, large-area fabrication method for developing SERS substrates, wherein not just batch processes but roll-to-roll fabrication processes are also possible. The low-cost textile fabric-based SERS substrates exhibit significantly higher SERS signals than those developed using GLAD on planar rigid silicon substrates or flexible Kapton substrates. This growth of plasmonic nanowires directly on the threads of a textile fabric has not been reported in any previous research work. Moreover, glancing angle deposition of plasmonic nanowires directly on a textile fabric has not been employed previously to develop large-area conformal SERS substrates. The SERS substrates developed on a large area can be cut into hundreds of small SERS sensor chips, which can be employed for detecting chemical or biological molecules of interest. The SERS analytical enhancement factor (AEF) of the textile fabric-based SERS sensor chips was experimentally evaluated to be 4×10 9 using pMBA. These SERS sensor chips were also employed for the label-free detection of DNA nucleobase cytosine (C).

Quasi-non-diffraction beam plays an important role in suppressing the divergence angle of the vortex electromagnetic wave. In this paper, a circular Pearcey beam is applied for orbital angular momentum (OAM) vortex beam’s divergence angle suppression, and a quasi-non-diffraction circular Pearcey vortex beam is generated with a transmission metasurface in the millimeter wave band. A full design method of the quasi-non-diffraction circular Pearcey vortex beam is proposed, and it is discussed in detail. An amplitude and phase controllable transmission metasurface working at 30 GHz is designed to generate a quasi-non-diffraction circular Pearcey (QCP) vortex beam with OAM mode of l = + 1. The simulated circular Pearcey vortex beam exhibits a distinct quasi-non-diffraction characteristic. Moreover, the circular Airy vortex beam and the conventional OAM vortex beam are also simulated and analyzed to compare with the designed Pearcey vortex beam. To further validate the proposed method, the designed transmission metasurface is fabricated and measured, and the measurement results align well with the simulation.

We demonstrate a high-quality source of polarization-entangled photons in aperiodically-poled KTiOPO 4 (KTP). The crystal is based on a phase-modulated domain-engineered design that allows two simultaneous downconversion processes, where the two processes correspond to the two terms of the entangled-photon state. We characterized the temperature tuning of both the spectral response and the polarization-fringe visibility for spontaneous parametric downconversion (SPDC) using this crystal. At the optimum temperature where wavelength distinguishability of the two SPDC processes is smallest, we obtained average polarization-entanglement visibility 0.984 ± 0.003 with a measured Clauser–Horne–Shimony–Holt (CHSH) parameter S = 2.801 ± 0.014. We also discuss the effects of the relative phase in the entangled-photon state and present a new way to compensate for these effects to obtain high polarization-entanglement visibility.

The crystallinity of a material often plays a significant role in determining its material properties. Aluminum nitride (AlN), which has emerged as a promising material for photonics in the past few decades, can be polycrystalline or monocrystalline in nature. Previously, the electro-optic (EO) coefficient of polycrystalline and bulk monocrystalline AlN has been reported. However, to the best of our knowledge, the EO coefficient of thin-film monocrystalline AlN has not yet been reported. In this work, we report the EO coefficient of thin-film monocrystalline AlN and make a side-by-side comparison with the EO coefficient of polycrystalline AlN. We used the resonant shift of a microring resonator to measure the EO coefficients for both transverse electric (TE) and transverse magnetic (TM) modes in the telecom C-band. For monocrystalline AlN, we observe surface effects that cause bias drift, which can be eliminated through annealing. The EO coefficients we measured for monocrystalline and polycrystalline AlN are comparable, with the EO of annealed monocrystalline AlN being slightly higher.