587 research outputs found
Coherent, directional supercontinuum via cascaded dispersive wave generation
We demonstrate a novel approach to producing coherent, directional
supercontinuum via cascaded dispersive wave generation. By pumping in the
normal group-velocity dispersion regime, pulse compression of the first
dispersive wave results in the generation of a second dispersive wave,
resulting in an octave-spanning supercontinuum generated primarily to one side
of the pump spectrum. We theoretically investigate the dynamics and show that
the generated spectrum is highly coherent. We experimentally confirm this
dynamical behavior and the coherence properties in silicon nitride waveguides
by performing direct detection of the carrier-envelope-offset frequency of our
femtosecond pump source using an f-2f interferometer. Our technique offers a
path towards a stabilized, high-power, integrated supercontinuum source with
low noise and high coherence, with applications including direct comb
spectroscopy
Gas-phase microresonator-based comb spectroscopy without an external pump laser
We present a novel approach to realize microresonator-comb-based high
resolution spectroscopy that combines a fiber-laser cavity with a
microresonator. Although the spectral resolution of a chip-based comb source is
typically limited by the free spectral range (FSR) of the microresonator, we
overcome this limit by tuning the 200-GHz repetition-rate comb over one FSR via
control of an integrated heater. Our dual-cavity scheme allows for
self-starting comb generation without the need for conventional pump-cavity
detuning while achieving a spectral resolution equal to the comb linewidth. We
measure broadband molecular absorption spectra of acetylene by interleaving 800
spectra taken at 250-MHz per spectral step using a 60-GHz-coarse-resolution
spectrometer and exploits advances of integrated heater which can locally and
rapidly change the refractive index of a microresonator with low electrical
consumption (0.9 GHz/mW), which is orders of magnitude lower than a fiber-based
comb. This approach offers a path towards a simple, robust and low-power
consumption CMOS-compatible platform capable of remote sensing
Synchronization of coupled optical microresonators
The phenomenon of synchronization occurs universally across the natural
sciences and provides critical insight into the behavior of coupled nonlinear
dynamical systems. It also offers a powerful approach to robust frequency or
temporal locking in diverse applications including communications,
superconductors, and photonics. Here we report the experimental synchronization
of two coupled soliton modelocked chip-based frequency combs separated over
distances of 20 m. We show that such a system obeys the universal Kuramoto
model for synchronization and that the cavity solitons from the microresonators
can be coherently combined which overcomes the fundamental power limit of
microresonator-based combs. This study could significantly expand applications
of microresonator combs, and with its capability for massive integration,
offers a chip-based photonic platform for exploring complex nonlinear systems
Low-Loss Silicon Platform for Broadband Mid-Infrared Photonics
Broadband mid-infrared (mid-IR) spectroscopy applications could greatly
benefit from today's well-developed, highly scalable silicon photonics
technology; however, this platform lacks broadband transparency due to its
reliance on absorptive silicon dioxide cladding. Alternative cladding materials
have been studied, but the challenge lies in decreasing losses while avoiding
complex fabrication techniques. Here, in contrast to traditional assumptions,
we show that silicon photonics can achieve low-loss propagation in the mid-IR
from 3 - 6 um wavelength, thus providing a highly scalable, well-developed
technology in this spectral range. We engineer the waveguide cross section and
optical mode interaction with the absorptive cladding oxide to reduce loss at
mid-IR wavelengths. We fabricate a microring resonator and measure an intrinsic
quality (Q) factor of 10^6 at wavelengths from 3.5 to 3.8 um. This is the
highest Q demonstrated on an integrated mid-IR platform to date. With this
high-Q silicon microresonator, we also demonstrate a low optical parametric
oscillation threshold of 5.2 mW, illustrating the utility of this platform for
nonlinear chip-scale applications in the mid-IR
Counter-rotating cavity solitons in a silicon nitride microresonator
We demonstrate the generation of counter-rotating cavity solitons in a
silicon nitride microresonator using a fixed, single-frequency laser. We
demonstrate a dual 3-soliton state with a difference in the repetition rates of
the soliton trains that can be tuned by varying the ratio of pump powers in the
two directions. Such a system enables a highly compact, tunable dual comb
source that can be used for applications such as spectroscopy and distance
ranging.Comment: 5pages, 5 figure
Fully integrated ultra-low power Kerr comb generation
Optical frequency combs are broadband sources that offer mutually-coherent,
equidistant spectral lines with unprecedented precision in frequency and timing
for an array of applications. Kerr frequency combs in microresonators require a
single-frequency pump laser and have offered the promise of highly compact,
scalable, and power efficient devices. Here, we realize this promise by
demonstrating the first fully integrated Kerr frequency comb source through use
of extremely low-loss silicon nitride waveguides that form both the
microresonator and an integrated laser cavity. Our device generates low-noise
soliton-modelocked combs spanning over 100 nm using only 98 mW of electrical
pump power. Our design is based on a novel dual-cavity configuration that
demonstrates the flexibility afforded by full integration. The realization of a
fully integrated Kerr comb source with ultra-low power consumption brings the
possibility of highly portable and robust frequency and timing references,
sensors, and signal sources. It also enables new tools to investigate the
dynamics of comb and soliton generation through close chip-based integration of
microresonators and lasers.Comment: 12 pages, 6 figure
A Reconfigurable Nanophotonics Platform for Sub-Millisecond, Deep Brain Neural Stimulation
Nanophotonics provides the ability to rapidly and precisely reconfigure light
beams on a compact platform. Infrared nanophotonic devices are widely used in
data communications to overcome traditional bandwidth limitations of electrical
interconnects. Nanophotonic devices also hold promise for use in biological
applications that require visible light, but this has remained technically
elusive due to the challenges of reconfiguring and guiding light at these
smaller dimensions. In neuroscience, for example, there is a need for
implantable optical devices to optogenetically stimulate neurons across deep
brain regions with the speed and precision matching state-of-the-art recording
probes. Here we demonstrate the first platform for reconfigurable nanophotonic
devices in the visible wavelength range and show its application in vivo in the
brain. We demonstrate an implantable probe endowed with the ability to rapidly
switch and route multiple optical beams using a nanoscale switching network.
Each switch consists of a silicon nitride waveguide structure that can be
reconfigured by electrically tuning the phase of light and is designed for
robustness to fabrication variation, enabling scalable devices. By implanting
our probe in mouse visual cortex, we demonstrate in vivo the ability to
stimulate identified sets of neurons across layers to produce multi-neuron
spike patterns and record them simultaneously with sub-millisecond temporal
precision. This nanophotonic platform can be scaled up and integrated with
high-density neural recording technologies, opening the door to implantable
probe technologies that are able to simultaneously record and stimulate the
activity of large neural populations at distant regions of the brain with
sub-millisecond precision. We expect this platform will enable researchers to
gain a deeper understanding into the spatio-temporal precision of the neural
code.Comment: 14 pages, 11 figure
Thermally Controlled Comb Generation and Soliton Modelocking in Microresonators
We report the first demonstration of thermally controlled soliton modelocked
frequency comb generation in microresonators. By controlling the electric
current through heaters integrated with silicon nitride microresonators, we
demonstrate a systematic and repeatable pathway to single- and multi-soliton
modelocked states without adjusting the pump laser wavelength. Such an approach
could greatly simplify the generation of modelocked frequency combs and
facilitate applications such as chip-based dual-comb spectroscopy.Comment: 5 pages, 6 figure
Observation of Arnold Tongues in Coupled Soliton Kerr Frequency Combs
We demonstrate various regimes of synchronization in systems of two coupled
cavity soliton-based Kerr frequency combs. We show sub-harmonic, harmonic and
harmonic-ratio synchronization of coupled microresonators, and reveal their
dynamics in the form of Arnold tongues, structures that are ubiquitous in
nonlinear dynamical systems. Our experimental results are well corroborated by
numerical simulations based on coupled Lugiato-Lefever equations. This study
illustrates the newfound degree of flexibility in synchronizing Kerr combs
across a wide range of comb spacings and could find applications in time and
frequency metrology, spectroscopy, microwave photonics, optical communications,
and astronomy
Near-degenerate quadrature-squeezed vacuum generation on a silicon-nitride chip
Squeezed states are a primary resource for continuous-variable (CV) quantum
information processing. To implement CV protocols in a scalable and robust way,
it is desirable to generate and manipulate squeezed states using an integrated
photonics platform. In this Letter, we demonstrate the generation of
quadrature-phase squeezed states in the radio-frequency carrier sideband using
a small-footprint silicon-nitride microresonator with a dual-pumped
four-wave-mixing process. We record a squeezed noise level of 1.34 dB
(0.16 dB) below the photocurrent shot noise, which corresponds to 3.09 dB
(0.49 dB) of quadrature squeezing on chip. We also show that it is
critical to account for the nonlinear behavior of the pump fields to properly
predict the squeezing that can be generated in this system. This technology
represents a significant step toward creating and manipulating large-scale CV
cluster states that can be used for quantum information applications including
universal quantum computing.Comment: 13 pages, 7 figure
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