For Very Long Baseline Interferometry high-resolution imaging of exoplanets, an astrophotonic-based aperture synthesis concept is proposed for high-resolution direct imaging of exoplanets. A silicon photonic chip incorporates microheaters and optical phase shifters for precise control of delays and phase synchronization from widely separated receivers. A satellite laser guide star with a modulated optical signal serves as a global phase reference, enabling high-speed, high-stroke phase compensation and combining. The chip's design addresses challenges such as atmospheric turbulence and phase stability in optical frequencies. The study outlines the current proof-of-concept instrument status, measured performance, chip fabrication, and routes towards photonics-enabled exoplanet imaging.
Integrated photonics can be used for stable, cost-effective and precision instruments in astronomy. We present our development and testing of a silicon ring resonator as a tunable correlation filter, facilitating real-time gas contrast for specific molecules with low cross-sensitivity. Ring resonators for various gases in H-band, polarization-selective filters, and fiber-coupled prototypes are described. We present the first on-sky demonstration of silicon-on-insulator astrophotonics, and telluric CO2 absorption feature detection as a proof-of-concept using the 1.2m DAO telescope and REVOLT adaptive optics instrument. Comparisons with traditional spectrographs inform discussions on improving performance and extensions towards an observatory-class instrument for exoplanet biosignature detection.
Over the past 15 years since their first demonstration, subwavelength grating metamaterials in silicon photonic devices have become widely used and attracted rapidly growing research interest while also breaking into commercial applications. We will discuss recent advances in this research field, with a focus on novel components and circuits for beam steering applications, on-chip filtering and quantum optics. On-chip optical waveguides comprised of Mie resonant particle chains have only recently been demonstrated and promise to be the foundation of a new and exciting branch of integrated metamaterials research. We will review the early work in this area.
Light scattered by subwavelength dielectric nanoantennas can be manipulated by engineering the antennas' Mie resonances. Spectral overlapping of the dipole-like electric and magnetic Mie resonances results in suppression of backward scattering. This phenomenon is known as Forward Kerker effect which enables the individual nanoantennas to act as Huygens' scatterers. A periodic chain of such Huygens' scatterers may effectively act as a so-called Huygens' metawaveguide with interesting new optical properties compared to non-resonant subwavelength grating waveguide counterparts. Inspiring by these recent findings, in our current research we are investigating more complex integrated photonic components, e.g., micro-ring resonators. In this talk, first I will explain the Forward Kerker effect of the resonant dielectric nanoantennas followed by the functionalities of a straight Huygens' metawaveguide. Next, I will demonstrate our high-Q Huygens' meta-ring-resonators and its different aspects. In conclusion, I will brief on the potential future applications of our demonstrated meta-ring-resonator in nonlinear and quantum integrated photonic systems.
Hyperpolarizability is a measure of the nonlinear optical characteristics of natural or meta-atoms describing how the atoms become nonlinearly polarized by the induced local-field. However, determining hyperpolarizability in the case of structured plasmonic meta-atoms is not straightforward due to their relatively larger sizes, unique shapes, and the index of refraction of the surrounding dielectric medium. Also, the order-of-magnitude of hyperpolarizability may vary with the frequency of light especially when inter-band transitions in metals become dominant. Here, we experimentally and theoretically estimated the order-of-magnitude of the 1st-order hyperpolarizability of gold meta-atoms that can be used in designing nonlinear metasurfaces.
Metasurfaces consisting of periodically arranged plasmonic nanoparticles could become a promising platform for optical filtering and nonlinear experiments. However, due to the high absorption loss of noble metals e.g. gold, the localized surface plasmon resonances (LSPR) of individual nanoparticles exhibit very low quality factors (Q ~ order of 10), which is not suitable for practical usage. Here, we experimentally demonstrate a plasmonic metasurface with ultra-high-Q (above 1000) surface lattice resonances (SLRs) around the optical telecommunication wavelength of 1550 nm by optimizing the LSPR of rectangular gold nanoparticles and the overall array size.
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