40 research outputs found
Nano-Kelvin thermometry and temperature control: beyond the thermal noise limit
We demonstrate thermometry with a resolution of 80 using an isotropic crystalline whispering-gallery mode
resonator based on a dichroic dual-mode technique. We simultaneously excite two
modes that have a mode frequency ratio very close to two (ppm). The
wavelength- and temperature-dependence of the refractive index means that the
frequency difference between these modes is an ultra-sensitive proxy of the
resonator temperature. This approach to temperature sensing automatically
suppresses sensitivity to thermal expansion and vibrationally induced changes
of the resonator. We also demonstrate active suppression of temperature
fluctuations in the resonator by controlling the intensity of the driving
laser. The residual temperature fluctuations are shown to be below the limits
set by fundamental thermodynamic fluctuations of the resonator material
Nano-Kelvin thermometry and temperature control: Beyond the thermal noise limit
We demonstrate thermometry with a resolution of 80nK/Hz using an isotropic crystalline whispering-gallery mode resonator based on a dichroic dual-mode technique. We simultaneously excite two modes that have a mode frequency ratio that is very close to two (±0.3ppm). The wavelength and temperature dependence of the refractive index means that the frequency difference between these modes is an ultrasensitive proxy of the resonator temperature. This approach to temperature sensing automatically suppresses sensitivity to thermal expansion and vibrationally induced changes of the resonator. We also demonstrate active suppression of temperature fluctuations in the resonator by controlling the intensity of the driving laser. The residual temperature fluctuations are shown to be below the limits set by fundamental thermodynamic fluctuations of the resonator material
Stabilization of a dynamically unstable opto-thermo-mechanical oscillator
We theoretically and experimentally examine thermal oscillations in a calcium fluoride whispering-gallery-mode resonator that lead to strong mode-frequency oscillations. We show that these oscillations arise from interplay among thermal expansion, the thermo-optic effect, and Kerr effects. In certain regimes we observe chaotic behavior and demonstrate that the threshold for this behavior can be predicted theoretically. We then demonstrate a self-stabilization technique that suppresses the oscillations and delivers high temperature and frequency stability without reference to external standards
Massively parallel coherent laser ranging using soliton microcombs
Coherent ranging, also known as frequency-modulated continuous-wave (FMCW)
laser based ranging (LIDAR) is currently developed for long range 3D distance
and velocimetry in autonomous driving. Its principle is based on mapping
distance to frequency, and to simultaneously measure the Doppler shift of
reflected light using frequency chirped signals, similar to Sonar or Radar.
Yet, despite these advantages, coherent ranging exhibits lower acquisition
speed and requires precisely chirped and highly-coherent laser sources,
hindering their widespread use and impeding Parallelization, compared to modern
time-of-flight (TOF) ranging that use arrays of individual lasers. Here we
demonstrate a novel massively parallel coherent LIDAR scheme using a photonic
chip-based microcomb. By fast chirping the pump laser in the soliton existence
range of a microcomb with amplitudes up to several GHz and sweep rate up to 10
MHz, the soliton pulse stream acquires a rapid change in the underlying carrier
waveform, while retaining its pulse-to-pulse repetition rate. As a result, the
chirp from a single narrow-linewidth pump laser is simultaneously transferred
to all spectral comb teeth of the soliton at once, and allows for true
parallelism in FMCW LIDAR. We demonstrate this approach by generating 30
distinct channels, demonstrating both parallel distance and velocity
measurements at an equivalent rate of 3 Mpixel/s, with potential to improve
sampling rates beyond 150 Mpixel/s and increase the image refresh rate of FMCW
LIDAR up to two orders of magnitude without deterioration of eye safety. The
present approach, when combined with photonic phase arrays based on
nanophotonic gratings, provides a technological basis for compact, massively
parallel and ultra-high frame rate coherent LIDAR systems.Comment: 18 pages, 12 Figure
Dynamics of soliton crystals in optical microresonators
Dissipative Kerr solitons in optical microresonators provide a unifying
framework for nonlinear optical physics with photonic-integrated technologies
and have recently been employed in a wide range of applications from coherent
communications to astrophysical spectrometer calibration. Dissipative Kerr
solitons can form a rich variety of stable states, ranging from breathers to
multiple-soliton formations, among which, the recently discovered soliton
crystals stand out. They represent temporally-ordered ensembles of soliton
pulses, which can be regularly arranged by a modulation of the continuous-wave
intracavity driving field. To date, however, the dynamics of soliton crystals
remains mainly unexplored. Moreover, the vast majority of the reported crystals
contained defects - missing or shifted pulses, breaking the symmetry of these
states, and no procedure to avoid such defects was suggested. Here we explore
the dynamical properties of soliton crystals and discover that often-neglected
chaotic operating regimes of the driven optical microresonator are the key to
their understanding. In contrast to prior work, we prove the viability of
deterministic generation of soliton crystal states, which
correspond to a stable, defect-free lattice of optical pulses inside the
cavity. We discover the existence of critical pump power, below which the
stochastic process of soliton excitation suddenly becomes deterministic
enabling faultless, device-independent access to perfect soliton crystals.
Furthermore, we demonstrate the switching of soliton crystal states and prove
that it is also tightly linked to the pump power and is only possible in the
regime of transient chaos. Finally, we report a number of other dynamical
phenomena experimentally observed in soliton crystals including the formation
of breathers, transitions between soliton crystals, their melting, and
recrystallization
Spectral purification of microwave signals with disciplined dissipative Kerr solitons
Continuous-wave-driven Kerr nonlinear microresonators give rise to
self-organization in terms of dissipative Kerr solitons, which constitute
optical frequency combs that can be used to generate low-noise microwave
signals. Here, by applying either amplitude or phase modulation to the driving
laser we create an intracavity potential trap, to discipline the repetition
rate of the solitons. We demonstrate that this effect gives rise to a novel
spectral purification mechanism of the external microwave signal frequency,
leading to reduced phase noise of the output signal. We experimentally observe
that the microwave signal generated from disciplined solitons follows the
external drive at long time scales, but exhibits an unexpected suppression of
the fast timing jitter. Counter-intuitively, this filtering takes place for
frequencies that are substantially lower than the cavity decay rate. As a
result, while the long-time-scale stability of the Kerr frequency comb
repetition rate is improved by more than 4 orders of magnitude as a result of
locking to the external microwave signal, the soliton stream shows a reduction
of the phase noise by 30 dB at offset frequencies above 10 kHz