Optics (physics.optics)

Abstract: This study presents the theoretical foundation for optimizing the enhanced-NA Fresnel hologram to recover the low space-bandwidth. Optical kernel functions in real and Fourier spaces act as a basis function in digital hologram synthesis. The higher spectrum components of the optical kernel functions beyond the bandwidth exists in the form of their replications. The expansion of angular spectrum of the digital hologram by its repetition during optimization procedure increases the image resolution, resulting in a viewing angle that is dependent on the hologram numerical aperture. We numerically and experimentally verify our strategy to implement a wide viewing-angle holographic display without shrinking the image size.

Abstract: Understanding light-matter interaction at the nanoscale requires probing the optical properties of matter at the individual nano-absorber level. To this end, we have developed a nanomechanical photothermal sensing platform that can be used as a full spectromicroscopy tool for single molecule and single particle analysis. As a demonstration, the absorption cross-section of individual gold nanorods is resolved from the spectroscopic and polarization standpoint. By exploiting the capabilities of nanomechanical photothermal spectromicroscopy, the longitudinal localized surface plasmon resonance (LSPR) in the NIR range is unravelled and quantitatively characterized. The polarization features of the transversal surface plasmon resonance (TSPR) in the VIS range are also analyzed. The measurements are compared with the finite element method (FEM), elucidating the role played by electron-surface and bulk scattering in these plasmonic nanostructures, as well as the interaction between the nano-absorber and the nanoresonator, ultimately resulting in an absorption strength modulation.

Abstract: Polygon and star modes enable unidirectional emission and single-frequency lasing in whispering gallery microcavities. To understand their properties and facilitate design, we have adopted both two-dimensional and three-dimensional full-wave perturbation methods to simulate these modes. Our simulation demonstrates that a tapered optical fiber can be used as a weak perturbation to coherently combine multiple whispering gallery modes into a polygon or star mode. Additionally, our simulation predicts an optical quality factor as high as $10^7$ for the polygon modes, which is in good agreement with the experiment results.