25 research outputs found
Opto-thermal transport engineering in hybrid organic-inorganic lead halide perovskites metasurfaces
Halide perovskites have recently gained widespread attention for their
exceptional optoelectronic properties which have been illuminated by extensive
spectroscopic investigations. In this article, nanophotonic surface-engineering
using soft-lithography has been used to reproduce nanostructures with enhanced
functionalities. A non-invasive optical technique based on Raman and
photolumines-cence (PL) spectroscopy is employed to investigate the interactive
effect of the thermal and optical behaviour in surface-patterned hybrid
organic-inorganic halide perovskite thin films. The thermophys-ical properties
of the engineered perovskite films are extracted from the softening of the
representa-tive peak positions in the Raman and PL spectra of the samples which
act as temperature markers. The investigation suggests a comparatively higher
rise in the local temperature for the patterned thin films resulting from their
enhanced absorption. Therefore, a cross-talk between the opto-thermal transport
phenomena in imprinted perovskite thin films pertaining to both enhancing
device properties along with maintaining device stability is established
Inversionless gain in a lossy medium
We study gain without inversion due to coherence effects in a
Doppler-broadened degenerate three-level system of a rubidium-hydrogen mixture
in a miniaturized micron scale custom vapor cell. The cell miniaturization
gives rise to collisions of atoms with the walls of the cell. This, combined
with the high collision rate with the hydrogen buffer gas allows us to observe
gain in the absorption spectra. Furthermore, we analyze the role of cell
miniaturization in the evolution of the gain profile. In addition to
fundamental interest, the observation of gain without inversion in our
miniaturized cells paves the way for applications such as miniaturized lasers
without inversion.Comment: 15 pages, 8 figures, 1 tabl
Near-IR wide field-of-view Huygens metalens for outdoor imaging applications
The ongoing effort to implement compact and cheap optical systems is the main
driving force for the recent flourishing research in the field of optical
metalenses. Metalenses are a type of metasurface, used for focusing and imaging
applications, and are implemented based on the nanopatterning of an optical
surface. The challenge faced by metalens research is to reach high levels of
performance, using simple fabrication methods suitable for mass-production. In
this paper we present a Huygens nanoantenna based metalens, designed for
outdoor photographic/surveillance applications in the near-infra-red. We show
that good imaging quality can be obtained over a field-of-view (FOV) as large
as +/-15 degrees. This first successful implementation of metalenses for
outdoor imaging applications is expected to provide insight and inspiration for
future metalens imaging applications
How good is your metalens? Experimental verification of metalens performance criterion
A metric for evaluation of overall metalens performance is presented. It is
applied to determination of optimal operating spectral range of a metalens,
both theoretically and experimentally. This metric is quite general and can be
applied to the design and evaluation of future metalenses, particularly
achromatic metalenses
On-Chip Integrated, Silicon-Graphene Plasmonic Schottky Photodetector with High Responsivity and Avalanche Photogain.
We report an on-chip integrated metal graphene-silicon plasmonic Schottky photodetector with 85 mA/W responsivity at 1.55 μm and 7% internal quantum efficiency. This is one order of magnitude higher than metal-silicon Schottky photodetectors operated in the same conditions. At a reverse bias of 3 V, we achieve avalanche multiplication, with 0.37A/W responsivity and avalanche photogain ∼2. This paves the way to graphene integrated silicon photonics.We acknowledge funding from EU Graphene Flagship (No. 604391), ERC Grant Hetero2D, and EPSRC Grant Nos. EP/ K01711X/1, EP/K017144/1, EP/N010345/1, EP/M507799/ 1, and EP/L016087/1.This is the final version of the article. It first appeared from the American Chemical Society via https://doi.org/10.1021/acs.nanolett.5b0521