The focal field of high NA lens axicon with a binary-phase optical component is calculated by using vector diffraction theory. Numerical results show that for a radially polarized Bessel Gaussian input field, the proposed system generates a subwavelength (0.395λ) longitudinally polarized beam with large uniform depth of focus (approximately 6 λ).

This numerical research presents a simple hybrid structure comprised of TiO₂-Cu-BaTiO₃ for a modified Kretschmann configuration that exhibits high sensitivity and high resolution for biosensing applications through an angular interrogation method. Recently, copper (Cu) emerged as an exceptional choice as a plasmonic metal for developing surface plasmon sensors (SPR) with high resolution as it yields finer, thinner SPR curves than Ag and Au. As copper is prone to oxidation, especially in ambient conditions, the proposed structure involves the utilization of barium titanate (BaTiO₃) film as a protection layer that not only preserves Cu film from oxidizing but enhances the performance of the sensor to a great extent. Numerical results also show that the utilization of a thin adhesive layer of titanium dioxide (TiO₂) between the prism base and Cu film not only induces strong interaction between them but also enhances the performance of the sensor. Such a configuration, upon suitable optimization of the thickness of each layer, is found to enhance sensitivity as high as 552°/RIU with a figure of merit (FOM) of 136.97 RIU⁻¹. This suggested biosensor design with enhanced sensitivity is expected to enable long-term detection with greater accuracy and sensitivity even when using Cu as a plasmonic metal.

We investigate the focusing properties of a double-ring-shaped azimuthally polarized beam by a high numerical aperture (NA) lens axicon based on vector diffraction theory. We observe that our proposed system generates a sub wavelength focal hole of $0.5\lambda$ having large uniform focal depth of $48\lambda$ without any annular aperture. We also observed that the distribution of the total intensity near the focus has little variation with the degree of truncation $\beta$ of the incident beam by the pupil. The authors expect such a super-long dark channel may find applications in optical, biological, and atmospheric sciences.

Optically transparent and mechanically good quality single crystal of L-Serine Phosphate (LSP) was grown by slow solvent evaporation technique. Optical Transmittance study was carried out by UV-Vis spectrophotometer. The optical Transmittance studies show the better transparency of the crystal in the ultraviolet and the entire visible region. Various optical constants such as optical band gap, absorption coefficient, extinction coefficient, reflectance, refractive index were calculated. Optical conductivity and electrical conductivity are also calculated using transmittance data. Important Mechanical properties of the grown crystal such as Vicker’s microhardness number, work hardening index, Yield strength, fracture toughness, brittleness index and elastic Stiffness constant values were determined using Vicker’s microhardness tester.