We explored the design of an optical pressure sensor. The objective is to create a photonic microelectromechanical system-based cantilever sensor design to detect prostate-specific antigen, a protein biomarker associated with prostate cancer. Sensor’s performance for the early detection of cancerous cells is dependent on sensitivity. The designed sensor consists of a hexagonal ring integrated with microcantilevers. Two types of microcantilever such as rectangular profile and V profile with integrated photonic sensing layer are investigated for sensitivity, quality factor, and resonant wavelength. The analysis shows that a geometrical modification of microcantilever has a significant effect on sensitivity enhancement. The finite difference time domain tool is used for designing photonic ring resonator patches. Numerical analysis of microcantilever is considered to investigate surface stress behavior. The cantilever deformation due to applied pressure resulted in a change in the index of refraction. Results show that the sensitivity of 55  nm  /  MPa for a triangular-shaped microcantilever obtained is higher compared to the rectangular-shaped microcantilever with a sensitivity of 0.19  nm  /  MPa. The designed structures have significantly higher sensitivities than the previously published sensitivity of 3.27  nm  /  MPa at wavelength 1550 nm. The maximum quality factor obtained for the rectangular shape is 2852 and 77,510 for the triangular shape. Triangular-shaped microcantilever can minimize winding inflexibility or stiffness. This capability of the triangular-shaped microcantilever enhances feasibility in making the final packaging and future fabrication.

We spin coated thin films of poly(methyl) methacrylate (PMMA) polymer doped with 2-[7-(1,3-dihydro-1,3,3-trimethyl-2H-indol-2-ylidene)-1,3,5-heptatrienyl]-1,3,3-trimethyl-3H-indolium iodide (HITC) laser dye onto microscope cover slides under applied flexural stress and found the patterns of scattering (milkiness) to correlate with the spatial variation of the pressure pattern. We further deposited thin gold films on top of the HITC:PMMA films and measured highly unusual transmission spectra of Au collected from strongly deformed (stressed) local areas of the sample. These spectra, which strongly deferred from those of plain Au films deposited onto unstressed glass, could not be described by simple, e.g., Maxwell Garnett, effective media models, calling for a thorough theoretical study.

We studied the electronic structure as well as the dielectric, optical, and phonon properties of PbTiO₃  /  CaTiO₃  /  SrTiO₃ ferroelectric superlattices, based on the density functional theory, using the Perdew–Becke–Johnson-generalized gradient approximation exchange-correlation functional. According to the results, the superlattice under investigation possessed a semiconducting phase with an indirect band gap of 1.84 eV. The results obtained for the partial density of states were indicative of a strong hybridization between the Ti-3d and O-2p states, which affected the amplitude of the Coulomb interaction and ferroelectric property. Regarding the optical properties, we calculated and analyzed the dielectric function and, accordingly, the refractive index, reflectivity, absorption coefficient, energy loss function, and optical conductivity. Thermal vibrations of the lattice were calculated along the high-symmetry path of the first Brillouin zone. Phonon dispersion data revealed stability at point Γ, while ferroelectric and dielectric responses of superlattice could be in unstable modes at other points of the Brillouin zone. Our results comprehensively present the electronic structure, dielectric function, plasmonic features, and dynamical stability based on phonon calculations, which are all essential for novel functional device applications.

A compact vertical coupler is proposed and optimized based on the multi-phase matching for three-dimensional (3D) mode (de)multiplexing [(De)MUX]. The multi-phase matching conditions can be achieved for the operating TE₂, TE₁, and TE₀ modes of the subwavelength grating-based waveguide. The coupling strength can be significantly increased due to the subwavelength structure. The proposed 3D mode (De)MUX is optimized by utilizing the 3D full-vectorial finite difference time domain method. The optimized mode (De)MUX can achieve the coupling lengths of only 0.25 and 1.75  μm for demultiplexing TE₁ and TE₂ modes. The insertion losses of the TE₂, TE₁, and TE₀ modes are only 0.25, 0.27, and 0.13 dB, respectively, and 3-dB bandwidths are calculated to be 364, 203, and >300  nm, respectively.

We proposed a hybrid metamaterial structure based on graphene–silver, which has tunable, efficient light-absorbing, and light-transmitting performance at the visible light regime. It is shown that this hybrid metamaterial structure can absorb light effectively with a maximum of 97.2% at a wavelength of 638 nm and reflect light effectively with a maximum of 98.05% at a wavelength of 437 nm. In addition, the two peak wavelength can be adjusted flexibly by grid voltage. This nearly perfect absorption capability is attributed to the synergetic effects of the localized surface plasmon enhancement of Ag nanoribbon, graphene plasmonics, metal–insulator–graphene mode, and Fabry–Perot resonance. There are almost no physical effects, only reflection when the reflection peak wavelength light goes into and out of the material. When the Fermi energy of graphene increases with the increase of grid voltage, the peaks wavelength of absorption and reflection will be blue shifted. This kind of tunable metamaterial can be used in visible light photodetectors or spectroscopy fields.

An optical amplitude modulator operating at near-infrared frequencies is presented. The proposed modulator structure consists of a Fabry–Perot (FP) cavity coupled with graphene located in the middle of two dielectric Bragg mirrors. Graphene’s presence as an active material with adjustable optical conductivity, as well as its effective interaction with powerful standing waves confined in the cavity, enables spectral tuning of the transmission spectrum. Since the resonator has a high quality factor, a small resonance frequency shift due to graphene Fermi energy change results in a huge change of the input light transmission value of the resonator, which makes it possible to achieve high modulation depth (MD). The results demonstrate that the proposed optical modulator has insertion loss lower than 0.1 and MD larger than 90%. It is believed that our study may be useful for optical wireless communication acting at near-infrared region.

Using the variational method of the Pekar type, we studied the ground-state energy and the excited-state energy of a parabolic potential quantum pseudodot. Through numerical calculation and derivation, we found that (1) the ground-state energy E₀ increases with the increase of V₀; (2) when λ  >  6, E₀ and E₁ are increasing functions of λ, but when λ  <  5, E₀ and E₁ are decreasing functions of λ. In these processes, the change of ω_c is not significant. (3) E₁ is a decreasing function of l₁ and l₂.

A surface plasmon-based hexagonal photonic crystal fiber sensor is numerically computed and studied covering a large span of analyte refractive index from 1.33 to 1.40. Structural design parameters are optimized to improve the sensor performance. Investigation of sensor sensitivity has been performed by analyzing the electromagnetic behavior of light using finite element method-based mode solver. The studied sensor yields the maximum amplitude sensitivity of 3958.84  RIU^−  1 at analyte RI of 1.39 and moderate wavelength sensitivity of 8000  nm RIU^−  1 at analyte RI of 1.40. The observed results are also presented by changing the gold layer thickness, lattice period, and air hole diameter. The reported plasmonic sensor is an appealing aspirant in the field of biochemical sensing, biomolecule detection, and biological sample recognition.

We report the synthesis of Ag–Au alloy nanoparticles (NPs) by post-irradiation of mixed colloidal Ag and Au NPs by a nanosecond pulse laser in the presence of an external electric field (EEF). In our study, size, optical, and plasmonic properties of colloidal Ag–Au alloy NPs were investigated. A colloid of individual Ag and Au NPs were separately prepared by nanosecond pulsed laser ablation in distilled water. An appropriate volume of these colloidal NPs samples was mixed and post-irradiated with the same pulsed laser beam in the presence of a uniform electric field, resulting in the formation of Ag–Au alloy NPs. The synthesized colloidal alloy NPs were characterized using scanning electron microscopy and UV–vis absorption spectroscopy. The results indicate that the EEF can reduce significantly the Ag–Au alloy formation time. The results also show that the wavelength of the localized surface plasmon resonance of alloy NPs decreased by the applied electric field.

Amyloid-based diseases, such as amyloid light-chain amyloidosis, are characterized by misfolding of proteins and their deposition as amyloids in tissues. As prognosis is usually poor, patients suffering from these illnesses can benefit from improved detection, monitoring, and treatment techniques. The use of nanoparticles to diagnose and treat biological targets has been extensively studied, including as a potential marker for Alzheimer’s disease, but not in the context of amyloidosis. Although curcumin is a known amyloid-binding molecule, vanillin attachment to amyloids has not been proposed or tested in the past. Our study focuses on iron oxide and gold nanoparticles, functionalized with curcumin and vanillin, as potential agents for amyloid specific binding. These nanoparticles are designed to have high visibility in computed tomography or magnetic resonance imaging and can therefore facilitate improved imaging and monitoring of amyloids. Amyloid fibers and plaques were prepared from insulin, and the successful binding of the nanoparticles to the amyloids was demonstrated using optical, fluorescence, and transmission electron microscopy. The nanoparticles did not bind to amyloids placed in cell-culture models, suggesting good specificity.

We propose an ultra-thin Huygens lens with high focusing efficiency and robustness that is composed of a unit cell with a pair of C-shaped split-ring resonators (CSRRs). Compared with the single-layer CSRR lens, the focusing efficiency of the Huygens metasurface lens improves 90% at the best focal lengths and three times at the central frequency. Our device has robustness against geometrical parameters, such as the difference of the opening angle, the mismatch of the opening angle, and the mismatch of the radius, which reduces the manufacturing difficulty. The Huygens lens has unprecedented potential for real-time, quick, electromagnetic wave processing such as holography, beam steering/splitter, imaging, and launcher control.

We design a dual-band absorber based on metal multiplexed gratings at mid-infrared (mid-IR) frequencies. The metal multiplexed gratings are realized with two constitutive gratings and separated from a metallic ground plate by a thick dielectric spacer in order to construct the metal–insulator–metal architecture. Simulations indicate that two different absorption frequencies from the excitation of surface plasmon–polariton modes can be achieved under normal incidence, due to the different field distributions of each resonance node numbers in supercell. The doublet resonance positions can be independently and arbitrarily adjusted by varying the constitutive grating periods. We also confirmed that the absorption performance of the resonance peak is related to the non-uniform distribution level of the corresponding constitutive grating ridge. The designed absorber can be easily fabricated with planar processing technology and used in many applications where multispectral control of mid-IR signals is required.

Avalanche photodiodes (APDs) are critical photodetection devices for high sensitivity and high-speed sensing. Great efforts in bandgap engineering and impact-ionization engineering have been put to achieve high gain-bandwidth products. Plasmonic optical antenna (POA) techniques can change the near-field distributions of the illumination light and thus provide an effective approach to achieve simultaneous enhancement of the gain and the detection speed. We report a metallic circular disk POA array-enhanced APD, where the circular disk POA array was fabricated on top of the p-doped side of the GaAs p-i-n APD. The electric field (E-field) distribution were simulated. The gain and the frequency response of the APD POA-enhanced APD were measured and compared with a reference APD without the POA array. The POA-enhanced APD shows a simultaneous enhancement in the gain and the detection speed.