JNP thanks the reviewers who served the journal in 2024.

Polarization beam splitters (PBSs) have received increasing attention due to their unique ability to split or combine two orthogonal linear polarization modes. We propose a compact all-fiber photonic crystal fiber-based terahertz (THz) PBS with a twin butterfly core. The design and optimization of the device are performed using the finite difference time domain method in combination with perfected matching layer boundary conditions. The influences of the PBS’s structural parameters on its coupling length as well as coupling length ratio are examined. The findings reveal that at 1 THz, the maximum polarization extinction ratio is 78.5 and 52.5 dB for x- and y-polarization lights, respectively, and it has an operation bandwidth of 24 GHz. The length of the PBS is merely 25.1 mm. Due to its remarkable characteristics and outstanding compatibility with the current THz optical fiber information system, the device will be widely applied in future THz radar, remote sensing, environmental monitoring, and imaging systems.

Artificial chiral structure plays an important role in the realization of strong chiroptical response and flexible light manipulation. Without introducing intrinsic chiral metamaterial with a complicated structure, we utilize a chiral metasurface to achieve giant extrinsic and tunable terahertz (THz) chirality assisted by quasi-bound states in the continuum (qBIC). The giant extrinsic chirality in this work originates from the mirror symmetry breaking of the proposed plasmonic THz metasurface; owing to the optical properties of InSb, the chirality induced by this metasurface can be actively manipulated by tailoring the angle of the elliptical nanopillar pairs and temperature. This proposed THz qBIC-assisted metasurface opens a new door for the detection of strong chirality, which may find potential important applications in THz science and technology, such as THz spin optics, chiral sensing, and efficient chiral light-emitting devices.

Although black phosphorous (BP) is a promising two-dimensional material for next-generation infrared (IR) photodetectors, enhancing its quantum efficiency remains challenging. We propose a hybrid BP/plasmonic nanograting with a narrow width and a high-depth groove system to address this challenge. The absorption properties of BP formed on plasmonic nanograting systems with two configurations, namely, an armchair edge normal and parallel to the groove direction, were numerically investigated. These systems demonstrated polarization-selective, wide-angle, near-unity absorption in the IR-wavelength region, and the absorption wavelength was controlled primarily by the groove depth. The BP induced a blue shift of the absorption wavelength, and the wavelength shift was larger for the armchair edge that was normal to the groove direction than that parallel to the groove direction. These results can be attributed to the coupling between the anisotropic surface plasmon resonances of BP and the plasmonic nanogratings. Moreover, this wavelength shift was enhanced by an increase in the carrier density of BP. The BP carrier density can be controlled by its electrical gating. This implies that the detection wavelength can be controlled by electrical gating of the BP. These systems can contribute to the development of high-performance BP-based polarization-selective and/or wavelength-tunable advanced IR photodetectors.

We design and experimentally demonstrate a four-channel cascaded Mach–Zehnder interferometer (MZI) with flat-passband for coarse wavelength division multiplexing, based on a silicon nitride platform. The performance of MZI filters is closely related to the design of power splitters. By employing wavelength-insensitive bent directional couplers between each MZI for power distribution, the crosstalk among channels within the device can be minimized. Simulation results indicate that the center crosstalk of all four channels is less than −24 dB, with a 3-dB bandwidth of ∼20 nm. Measurement results show that the average crosstalk between adjacent channels is −16.5 dB. The 3-dB bandwidths of the four channels are ∼19.7, 19.3, 19.3, and 20.5 nm, respectively. Compared with conventional cascaded MZI devices using straight directional couplers, the bent DC-based device shows a clear advantage in crosstalk performance. This work is conducive to promoting the commercial application of such a device.

The valence band structure and optical transitions of holes are investigated for elongated InGaAs/GaAs quantum dot (QD). We use the 4×4 Luttinger Hamiltonian under effective mass approximation for the estimation of the valence band structure. The energy eigenvalues and corresponding eigenvectors have been calculated by numerical diagonalization of Hamiltonian for lens-shaped QD using the harmonic oscillator basis function without considering the strain effect. We analyzed the impact of the size and composition of the QD on valence band structure and the transition probability of holes from ground state to excited states. The analysis reveals that the hole energy states form the energy band of heavy-hole (hh) and light-hole (lh) states. The band mixing of hh and lh energy states is decreasing with an increase in the lateral dimension (LD) of the QD which is indicated by the increase in the hh-lh band offset (Boff) parameter. The hh and lh states show strong intermixing for the small values of indium (In) concentration less than 0.23 and for the LD less than 10 nm for which the Boff parameter is found to be less than 25.22 meV. The widths of hh and lh bands are found to decrease with an increase in LD, and it is increasing with In concentration of the QD. The transitions from hh to hh states are polarization-sensitive, but transitions from hh to lh states are insensitive to the polarization state of the incident photon. The square optical matrix elements are decreasing with LD and increasing with In concentration.

The research into 6G communication technology is intense, providing a focal point for terahertz metamaterials, with high-performance 6G communication sensors being a prominent area of interest. Drawing on the distinctive features of our university’s emblem, this study explores 4F rotating nanoperiodic metamaterials, leading to the design and fabrication of a wide-angle, non-polarized terahertz receiver sensor utilizing 4F rotating structure metamaterials. The 4F rotating periodic nanoscale metamaterials comprise copper-based, silicon dioxide, aluminum oxide, graphene, and a periodic 4F rotating structure of gold material metal pattern layer. Leveraging mechanisms such as Fabry-Pérot resonance, surface plasmon effects of nano metal patterns, and graphene Fermi level control, the material exhibits two nearly perfect absorption edges that can be gate-regulated within the 1 to 3 THz range. Based on these metamaterials, the sensor’s gate control voltage shows a clear linear relationship, achieving a Fermi level tuning of 3.2 mV corresponding to 0.2 eV, and a peak blue shift of 0.05 THz. The sensor maintains a stable absorption spectrum under both transverse magnetic and transverse electric modes, with the absorption rate dropping by <50% within an incident angle of 75 deg, and controlled at 80% within 60 deg. These unique characteristics are poised to make this sensor the new darling of 6G communication.