645 research outputs found
Hybrid Electro-Optically Modulated Microcombs
Optical frequency combs based on mode-locked lasers have proven to be
invaluable tools for a wide range of applications in precision spectroscopy and
metrology. A novel principle of optical frequency comb generation in
whispering-gallery mode microresonators ("microcombs") has been developed
recently, which represents a promising route towards chip-level integration and
out-of-the-lab use of these devices. Presently, two families of microcombs have
been demonstrated: combs with electronically detectable mode spacing that can
be directly stabilized, and broadband combs with up to octave-spanning spectra
but mode spacings beyond electronic detection limits. However, it has not yet
been possible to achieve these two key requirements simultaneously, as will be
critical for most microcomb applications. Here we present a key step to
overcome this problem by interleaving an electro-optic comb with the spectrum
from a parametric microcomb. This allows, for the first time, direct control
and stabilization of a microcomb spectrum with large mode spacing (>140 GHz)
with no need for an additional mode-locked laser frequency comb. The attained
residual 1-second-instability of the microcomb comb spacing is 10^-15, with a
microwave reference limited absolute instability of 10^-12 at a 140 GHz mode
spacing.Comment: 8 pages, 4 figures; accepted for publication in Physical Review
Letter
Parametric seeding of a microresonator optical frequency comb
We have investigated parametric seeding of a microresonator frequency comb
(microcomb) by way of a pump laser with two electro-optic-modulation sidebands.
We show that the pump-sideband spacing is precisely replicated throughout the
microcomb's optical spectrum, and we demonstrate a record absolute line-spacing
stability for microcombs of at 1 s. The spectrum of a
parametric comb is complex, and often non-equidistant subcombs are observed.
Our results demonstrate that parametric seeding can not only control the
subcombs, but can lead to the generation of a strictly equidistant microcomb
spectrum.Comment: 10 pages, 5 figure
Short-range force detection using optically-cooled levitated microspheres
We propose an experiment using optically trapped and cooled dielectric
microspheres for the detection of short-range forces. The center-of-mass motion
of a microsphere trapped in vacuum can experience extremely low dissipation and
quality factors of , leading to yoctonewton force sensitivity.
Trapping the sphere in an optical field enables positioning at less than 1
m from a surface, a regime where exotic new forces may exist. We expect
that the proposed system could advance the search for non-Newtonian gravity
forces via an enhanced sensitivity of over current experiments at
the 1 m length scale. Moreover, our system may be useful for
characterizing other short-range physics such as Casimir forces.Comment: 4 pages, 3 figures, minor changes, Figs. 1 and 2 replace
Soliton crystals in Kerr resonators
Strongly interacting solitons confined to an optical resonator would offer
unique capabilities for experiments in communication, computation, and sensing
with light. Here we report on the discovery of soliton crystals in monolithic
Kerr microresonators-spontaneously and collectively ordered ensembles of
co-propagating solitons whose interactions discretize their allowed temporal
separations. We unambiguously identify and characterize soliton crystals
through analysis of their 'fingerprint' optical spectra, which arise from
spectral interference between the solitons. We identify a rich space of soliton
crystals exhibiting crystallographic defects, and time-domain measurements
directly confirm our inference of their crystal structure. The crystallization
we observe is explained by long-range soliton interactions mediated by
resonator mode degeneracies, and we probe the qualitative difference between
soliton crystals and a soliton liquid that forms in the absence of these
interactions. Our work explores the rich physics of monolithic Kerr resonators
in a new regime of dense soliton occupation and offers a way to greatly
increase the efficiency of Kerr combs; further, the extreme degeneracy of the
configuration space of soliton crystals suggests an implementation for a robust
on-chip optical buffer
Self-referencing a continuous-wave laser with electro-optic modulation
We phase-coherently measure the frequency of continuous-wave (CW) laser light
by use of optical-phase modulation and f-2f nonlinear interferometry. Periodic
electro-optic modulation (EOM) transforms the CW laser into a continuous train
of picosecond optical pulses. Subsequent nonlinear-fiber broadening of this EOM
frequency comb produces a supercontinuum with 160 THz of bandwidth. A critical
intermediate step is optical filtering of the EOM comb to reduce
electronic-noise-induced decoherence of the supercontinuum. Applying f-2f
self-referencing with the supercontinuum yields the carrier-envelope offset
frequency of the EOM comb, which is precisely the difference of the CW laser
frequency and an exact integer multiple of the EOM pulse repetition rate. Here
we demonstrate absolute optical frequency metrology and synthesis applications
of the self-referenced CW laser with <5E-14 fractional accuracy and stability.Comment: 8 pages, 4 figure
Mechanical control of a microrod-resonator optical frequency comb
Robust control and stabilization of optical frequency combs enables an
extraordinary range of scientific and technological applications, including
frequency metrology at extreme levels of precision, novel spectroscopy of
quantum gases and of molecules from visible wavelengths to the far infrared,
searches for exoplanets, and photonic waveform synthesis. Here we report on the
stabilization of a microresonator-based optical comb (microcomb) by way of
mechanical actuation. This represents an important step in the development of
microcomb technology, which offers a pathway toward fully-integrated comb
systems. Residual fluctuations of our 32.6 GHz microcomb line spacing reach a
record stability level of for 1 s averaging, thereby
highlighting the potential of microcombs to support modern optical frequency
standards. Furthermore, measurements of the line spacing with respect to an
independent frequency reference reveal the effective stabilization of different
spectral slices of the comb with a 0.5 mHz variation among 140 comb lines
spanning 4.5 THz. These experiments were performed with newly-developed
microrod resonators, which were fabricated using a CO-laser-machining
technique
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