12,923 research outputs found
A Passively Mode-locked Nanosecond Laser with an Ultra-narrow Spectral Width
Many different mode-locking techniques have been realized in the past [1, 2], but mainly focused on increasing the spectral bandwidth to achieve ultra-short coherent light pulses with well below picosecond duration. In contrast, no mode-locked laser scheme has managed to generate Fourier-limited nanosecond long pulses, which feature narrow spectral bandwidths (~MHz regime) instrumental to applications in spectroscopy, efficient excitation of molecules, sensing, and quantum optics. The related limitations are mainly caused by the adverse operation timescales of saturable absorbers, as well as by the low strength of the nonlinear effects typically reachable through nanosecond pulses with manageable energies
Plasmonic nanoantennas as integrated coherent perfect absorbers on SOI waveguides for modulators and all-optical switches
The performance of plasmonic nanoantenna structures on top of SOI wire
waveguides as coherent perfect absorbers for modulators and all-optical
switches is explored. The absorption, scattering, reflection and transmission
spectra of gold and aluminum nanoantenna-loaded waveguides were calculated by
means of 3D finite-difference time-domain simulations for single waves
propagating along the waveguide, as well as for standing wave scenarios
composed from two counterpropagating waves. The investigated configurations
showed losses of roughly 1% and extinction ratios greater than 25 dB for
modulator and switching applications, as well as plasmon effects such as strong
field enhancement and localization in the nanoantenna region. The proposed
plasmonic coherent perfect absorbers can be utilized for ultracompact
all-optical switches in coherent networks as well as modulators and can find
applications in sensing or in increasing nonlinear effects.Comment: 10 pages, 6 figure
Incoherent "Slow and Fast Light"
We show experimentally that the effects of "slow and fast light" that are
considered to be caused by spectral hole-burning under conditions of coherent
population oscillations (CPO) can be universally observed with incoherent light
fields on objects with the pure-intensity nonlinearity, when such an
interpretation is inapplicable. As a light source, we used an incandescent lamp
and as objects for study, a photochromic glass and a thermochromic coating. The
response of the objects to intensity modulation of the incident light
reproduced in all details the commonly accepted experimental evidences of the
"light with a negative group velocity" and "ultraslow light". We come to
conclusion that so far there are no experimental works providing evidence for
real observation of the "CPO-based slow or fast light".Comment: 10 pages and 8 figure
Tunable broadband light emission from graphene
Graphene is an ideal material for integrated nonlinear optics thanks to its
strong light-matter interaction and large nonlinear optical susceptibility.
Graphene has been used in optical modulators, saturable absorbers, nonlinear
frequency converters, and broadband light emitters. For the latter application,
a key requirement is the ability to control and engineer the emission
wavelength and bandwidth, as well as the electronic temperature of graphene.
Here, we demonstrate that the emission wavelength of graphene s broadband
hot carrier photoluminescence can be tuned by integration on photonic cavities,
while thermal management can be achieved by out-of-plane heat transfer to
hexagonal boron nitride. Our results pave the way to graphene-based ultrafast
broadband light emitters with tunable emission.Comment: 22 pages, 5 Figure
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