24 research outputs found
Soliton generation in CaF crystalline whispering gallery mode resonators with negative thermal-optical effects
Calcium fluoride (CaF) crystalline whispering gallery mode resonators
(WGMRs) exhibit ultrahigh intrinsic quality factors and a low power anomalous
dispersion in the communication and mid-infrared bands, making them attractive
platforms for microresonator-based comb generation. However, their unique
negative thermo-optic effects pose challenges when achieving thermal
equilibrium. To our knowledge, our experiments serve as the first demonstration
of soliton microcombs in Q > 109 CaF WGMRs. We observed soliton
mode-locking and bidirectional switching of soliton numbers caused by the
negative thermo-optic effects. Additionally, various soliton formation dynamics
are shown, including breathing and vibrational solitons, which can be
attributed to thermo-photomechanical oscillations. Thus, our results enrich the
soliton generation platform and provide a reference for generating solitons
from WGMRs that comprise other materials with negative thermo-optic effects. In
the future, the ultrahigh quality factor of CaF crystal cavities may enable
the generation of sub-milliwatt-level broad-spectrum soliton combs.Comment: 4 pages,5 pictures,description of soliton generation in a calcium
fluoride whisper gallery mode microresonators with negative thermo-optical
effect,ready for publication in optics lette
Direct Kerr-frequency-comb atomic spectroscopy
Microresonator-based soliton frequency combs - microcombs - have recently
emerged to offer low-noise, photonic-chip sources for optical measurements.
Owing to nonlinear-optical physics, microcombs can be built with various
materials and tuned or stabilized with a consistent framework. Some
applications require phase stabilization, including optical-frequency synthesis
and measurements, optical-frequency division, and optical clocks. Partially
stabilized microcombs can also benefit applications, such as oscillators,
ranging, dual-comb spectroscopy, wavelength calibration, and optical
communications. Broad optical bandwidth, brightness, coherence, and frequency
stability have made frequency-comb sources important for studying comb-matter
interactions with atoms and molecules. Here, we explore direct microcomb atomic
spectroscopy, utilizing a cascaded, two-photon 1529-nm atomic transition of
rubidium. Both the microcomb and the atomic vapor are implemented with planar
fabrication techniques to support integration. By fine and simultaneous control
of the repetition rate and carrier-envelope-offset frequency of the soliton
microcomb, we obtain direct sub-Doppler and hyperfine spectroscopy of the
manifold. Moreover, the entire set of microcomb modes are
stabilized to this atomic transition, yielding absolute optical-frequency
fluctuations of the microcomb at the kilohertz-level over a few seconds and < 1
MHz day-to-day accuracy. Our work demonstrates atomic spectroscopy with
microcombs and provides a rubidium-stabilized microcomb laser source, operating
across the 1550 nm band for sensing, dimensional metrology, and communication.Comment: 5 pages, 3 figure
Towards a compact soliton microcomb fully referenced on atomic reference
A fully stabilized soliton microcomb is critical for many applications of
optical frequency comb based on microresonators. However, the current
approaches for full frequency stabilization require either external
acousto-optic or electro-optic devices or auxiliary lasers and multiple
phase-locked loops, which compromises the convenience of the system. This study
explores a compact atomic referenced fully stabilized soliton microcomb that
directly uses a rubidium atomic optical frequency reference as the pump source,
and complements the repetition rate (7.3 GHz) of the soliton microcomb was
phase-locked to an atomic-clock-stabilized radio frequency (RF) reference by
mechanically tuning the resonance of the optical resonator. The results
demonstrate that the stability of the comb line (0.66 THz away from the pump
line) is consistent with that of the Rb87 optical reference, attaining a level
of approximately 4 Hz @100 s, corresponding to the frequency stability of 2E-14
@100 s. Furthermore,the frequency reproducibility of the comb line was
evaluated over six days and it was discovered that the standard deviation (SD)
of the frequency of the comb line is 10 kHz, resulting in a corresponding
absolute deviation uncertainty of 1.3E-10, which is technically limited by the
locking range of the soliton repetition rate. The proposed method gives a
low-power and compact solution for fully stabilized soliton micorcombs.Comment: 6 pages, 5 figure
Direct Kerr frequency comb atomic spectroscopy and stabilization
Microresonator-based soliton frequency combs, microcombs, have recently emerged to offer low-noise, photonic-chip sources for applications, spanning from timekeeping to optical-frequency synthesis and ranging. Broad optical bandwidth, brightness, coherence, and frequency stability have made frequency combs important to directly probe atoms and molecules, especially in trace gas detection, multiphoton light-atom interactions, and spectroscopy in the extreme ultraviolet. Here, we explore direct microcomb atomic spectroscopy, using a cascaded, two-photon 1529-nm atomic transition in a rubidium micromachined cell. Fine and simultaneous repetition rate and carrier-envelope offset frequency control of the soliton enables direct sub-Doppler and hyperfine spectroscopy. Moreover, the entire set of microcomb modes are stabilized to this atomic transition, yielding absolute optical-frequency fluctuations at the kilohertz level over a few seconds and <1-MHz day-to-day accuracy. Our work demonstrates direct atomic spectroscopy with Kerr microcombs and provides an atomic-stabilized microcomb laser source, operating across the telecom band for sensing, dimensional metrology, and communication
Direct Kerr frequency comb atomic spectroscopy and stabilization
Microresonator-based soliton frequency combs, microcombs, have recently emerged to offer low-noise, photonic-chip sources for applications, spanning from timekeeping to optical-frequency synthesis and ranging. Broad optical bandwidth, brightness, coherence, and frequency stability have made frequency combs important to directly probe atoms and molecules, especially in trace gas detection, multiphoton light-atom interactions, and spectroscopy in the extreme ultraviolet. Here, we explore direct microcomb atomic spectroscopy, using a cascaded, two-photon 1529-nm atomic transition in a rubidium micromachined cell. Fine and simultaneous repetition rate and carrier-envelope offset frequency control of the soliton enables direct sub-Doppler and hyperfine spectroscopy. Moreover, the entire set of microcomb modes are stabilized to this atomic transition, yielding absolute optical-frequency fluctuations at the kilohertz level over a few seconds and <1-MHz day-to-day accuracy. Our work demonstrates direct atomic spectroscopy with Kerr microcombs and provides an atomic-stabilized microcomb laser source, operating across the telecom band for sensing, dimensional metrology, and communication