In polarimetry, that is, a measurement of the four-component polarization Stokes vector, a measurement must either consist of four (or more) sequential intensity measurements, sacrificing time resolution, or contain four separate light paths each with separate polarization optics, increasing bulk, cost, and system complexity. Similar issues present difficulty across polarization optics technology.
Metasurfaces, nanophotonic arrays of phase shifting elements, have emerged as a novel platform for polarization optics. These individual phase shifters can be designed with a characteristic anisotropy, and are thus imbued with tunable shape birefringence. A metasurface, then, can function as a subwavelength spaced array of nanoscale waveplates.
I will describe how, through relatively simple optimization methods, a metasurface producing arbitrarily specified polarization states (when illuminated with light of a known polarization) can be designed. This functionality is equivalent to a traditional diffraction grating with individual waveplate optics on each order; here, all the necessary polarization optics can be integrated into a flat, ultrathin optical element. Moreover, such a metasurface can be used in a reverse configuration as a parallel snapshot polarimeter with no need for additional polarization optics (save for a single polarizer). I present a detailed experimental characterization of both concepts in the visible spectral region and a comparison of the performance of the metasurface to a commercially available rotating waveplate polarimeter. With no bulk birefringent crystal optics, a parallel, full-polarization state measurement can be made with an integrated, scalable, and inexpensive device. Given its diffractive nature, the design naturally extends to spectropolarimetry and polarization imaging.
Optical amplification of surface plasmon polaritons has been pursued extensively in recent years. However, few currently known optical gain materials can be expected to provide sufficient gain to fully compensate propagation losses of highly confined surface plasmon polaritons. Low-loss plasmonic waveguide geometries, on the other hand, provide a platform for realizing net plasmon gain by sacrificing some plasmonic properties. In search for potential applications for amplified surface plasmon polaritons, focus should be on making use of both optical gain and optical loss, such as in high-extinction-ratio modulators or parity-time symmetric devices.
A novel optical platform offering potential for highly integrated polymer-based biophotonic chips is presented, featuring
a cladding index that closely matches aqueous samples or biological samples. Applications including evanescent-wave
microscopy, surface plasmon-coupled biosensing, and on-chip manipulation of light signals are demonstrated.
We present simulations of integrated optical devices based on nanometer-thin metallic stripes or wires suitable for
guiding long-range surface plasmon polaritons at telecom wavelengths. Propagation of light in these circuits can be
directly controlled by using the metal wires simultaneously as waveguides and heating elements. We will show examples
of how resistive heating of metallic waveguides can be used to control confinement or used to affect selected parts of
multi-mode waveguides in order to realize modulation, attenuation and/or switching.
We report on experimental realization of different metal-insulator geometries that are used as plasmonic waveguides
guiding electromagnetic radiation along metal-dielectric interfaces via excitation of surface plasmon polaritons (SPPs).
Three configurations are considered: metal strips, symmetric nanowires and nanowire pairs embedded in a dielectric, and
metal V-shaped grooves. Planar plasmonic waveguides based on nm-thin and μm-wide gold strips embedded in a
polymer that support propagation of long-range SPPs are shown to constitute an alternative for integrated optical
circuits. Using uniform and thickness-modulated gold strips different waveguide components including reflecting
gratings can be realized. For applications where polarization is random or changing, metal nanowire waveguides are
shown to be suitable candidates for efficient guiding of arbitrary polarized light. Plasmonic waveguides based on metal
V-grooves that offer subwavelength confinement are also considered. We focus on recent advances in manufacturing of
nanostructured metal strips and metal V-grooves using combined UV, electron-beam and nanoimprint lithography.
Long-range surface plasmon polariton (LRSPP) waveguides supporting both TE and TM polarized light are demonstrated experimentally. The waveguides consist of metallic nanowires with approximately 150-nm square cross sections embedded in a polymer matrix. The wavelength dependence of propagation loss and coupling loss to single mode fibers is presented. At wavelengths around 1550 nm, the nanowires exhibit a propagation loss around 4.0 dB/cm for the TM mode and 4.5 dB/cm for the TE mode. The mode field is close to symmetric and suitable for coupling to and from optical fibers. A small increase in the waveguide width, resulting in a deviation from a square cross section, is sufficient to extinguish the TE mode, making asymmetric nanowire waveguides similar to the more conventional LRSPP thin stripe waveguides. Finally, we demonstrate a compact thermo-optical variable optical attenuator based on a LRSPP nanowire waveguide.