4,500 research outputs found
Enhanced Photodetection in Graphene-Integrated Photonic Crystal Cavity
We demonstrate the controlled enhancement of photoresponsivity in a graphene
photodetector by coupling to slow light modes in a long photonic crystal linear
defect cavity. Near the Brillouin zone (BZ) boundary, spectral coupling of
multiple cavity modes results in broad-band photocurrent enhancement from 1530
nm to 1540 nm. Away from the BZ boundary, individual cavity resonances enhance
the photocurrent eight-fold in narrow resonant peaks. Optimization of the
photocurrent via critical coupling of the incident field with the
graphene-cavity system is discussed. The enhanced photocurrent demonstrates the
feasibility of a wavelength-scale graphene photodetector for efficient
photodetection with high spectral selectivity and broadband response
Electrical detection of hyperbolic phonon-polaritons in heterostructures of graphene and boron nitride
Light properties in the mid-infrared can be controlled at a deep
subwavelength scale using hyperbolic phonons-polaritons (HPPs) of hexagonal
boron nitride (h-BN). While propagating as waveguided modes HPPs can
concentrate the electric field in a chosen nano-volume. Such a behavior is at
the heart of many applications including subdiffraction imaging and sensing.
Here, we employ HPPs in heterostructures of h-BN and graphene as new
nano-optoelectronic platform by uniting the benefits of efficient hot-carrier
photoconversion in graphene and the hyperbolic nature of h-BN. We demonstrate
electrical detection of HPPs by guiding them towards a graphene pn-junction. We
shine a laser beam onto a gap in metal gates underneath the heterostructure,
where the light is converted into HPPs. The HPPs then propagate as confined
rays heating up the graphene leading to a strong photocurrent. This concept is
exploited to boost the external responsivity of mid-infrared photodetectors,
overcoming the limitation of graphene pn-junction detectors due to their small
active area and weak absorption. Moreover this type of detector exhibits
tunable frequency selectivity due to the HPPs, which combined with its high
responsivity paves the way for efficient high-resolution mid-infrared imaging
Monolayer graphene bolometer as a sensitive far-IR detector
In this paper we give a detailed analysis of the expected sensitivity and
operating conditions in the power detection mode of a hot-electron bolometer
(HEB) made from a few {\mu}m of monolayer graphene (MLG) flake which can be
embedded into either a planar antenna or waveguide circuit via NbN (or NbTiN)
superconducting contacts with critical temperature ~ 14 K. Recent data on the
strength of the electron-phonon coupling are used in the present analysis and
the contribution of the readout noise to the Noise Equivalent Power (NEP) is
explicitly computed. The readout scheme utilizes Johnson Noise Thermometry
(JNT) allowing for Frequency-Domain Multiplexing (FDM) using narrowband filter
coupling of the HEBs. In general, the filter bandwidth and the summing
amplifier noise have a significant effect on the overall system sensitivity.
The analysis shows that the readout contribution can be reduced to that of the
bolometer phonon noise if the detector device is operated at 0.05 K and the JNT
signal is read at about 10 GHz where the Johnson noise emitted in equilibrium
is substantially reduced. Beside the high sensitivity (NEP < 10
W/Hz, this bolometer does not have any hard saturation limit and thus
can be used for far-IR sky imaging with arbitrary contrast. By changing the
operating temperature of the bolometer the sensitivity can be fine tuned to
accommodate the background photon flux in a particular application. By using a
broadband low-noise kinetic inductance parametric amplifier, ~100s of graphene
HEBs can be read simultaneously without saturation of the system output.Comment: 9 pages. 6 figure, SPIE Astronomical Telescopes + Instrumentation,
Montr\'eal, Quebec, Canada, 22-27 June, 201
Graphene-based Josephson junction single photon detector
We propose to use graphene-based Josephson junctions (gJjs) to detect single
photons in a wide electromagnetic spectrum from visible to radio frequencies.
Our approach takes advantage of the exceptionally low electronic heat capacity
of monolayer graphene and its constricted thermal conductance to its phonon
degrees of freedom. Such a system could provide high sensitivity photon
detection required for research areas including quantum information processing
and radio-astronomy. As an example, we present our device concepts for gJj
single photon detectors in both the microwave and infrared regimes. The dark
count rate and intrinsic quantum efficiency are computed based on parameters
from a measured gJj, demonstrating feasibility within existing technologies.Comment: 11 pages, 6 figures, and 1 table in the main tex
Femtosecond Population Inversion and Stimulated Emission of Dense Dirac Fermions in Graphene
We show that strongly photoexcited graphene monolayers with 35fs pulses
quasi-instantaneously build up a broadband, inverted Dirac fermion population.
Optical gain emerges and directly manifests itself via a negative optical
conductivity for the first 200fs, where stimulated emission completely
compensates absorption loss in the graphene layer. Our experiment-theory
comparison with two distinct electron and hole chemical potentials reproduce
absorption saturation and gain at 40fs, revealing, particularly, the evolution
of the transient state from a hot classical gas to a dense quantum fluid with
increasing the photoexcitation
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