57 research outputs found
Chaos-assisted two-octave-spanning microcombs
Since its invention, optical frequency comb has revolutionized a broad range of subjects from metrology to spectroscopy. The recent development of microresonator-based frequency combs (microcombs) provides a unique pathway to create frequency comb systems on a chip. Indeed, microcomb-based spectroscopy, ranging, optical synthesizer, telecommunications and astronomical calibrations have been reported recently. Critical to many of the integrated comb systems is the broad coverage of comb spectra. Here, microcombs of more than two-octave span (450 nm to 2,008 nm) is demonstrated through χ^((2)) and χ^((3)) nonlinearities in a deformed silica microcavity. The deformation lifts the circular symmetry and creates chaotic tunneling channels that enable broadband collection of intracavity emission with a single waveguide. Our demonstration introduces a new degree of freedom, cavity deformation, to the microcomb studies, and our microcomb spectral range is useful for applications in optical clock, astronomical calibration and biological imaging
On-chip Q-factor greater than 1 billion
A record Q-factor of 1.1 billion is demonstrated in on-chip silica whispering-gallery resonators. Using the devices, sub-milliwatt parametric oscillation threshold is measured in 9 GHz free-spectral-range devices
On-chip Q-factor greater than 1 billion
A record Q-factor of 1.1 billion is demonstrated in on-chip silica whispering-gallery resonators. Using the devices, sub-milliwatt parametric oscillation threshold is measured in 9 GHz free-spectral-range devices
Impact of spatio-temporal thermal decoherence on soliton microcombs in multimode microresonators
The phase noise of the soliton repetition rate is experimentally characterized in silica microresonators. In conjunction with dispersive wave quieting of pump technical noise, spatio-temporal fluctuations of distinct transverse modes set a limit to performance
Impact of spatio-temporal thermal decoherence on soliton microcombs in multimode microresonators
The phase noise of the soliton repetition rate is experimentally characterized in silica microresonators. In conjunction with dispersive wave quieting of pump technical noise, spatio-temporal fluctuations of distinct transverse modes set a limit to performance
Soliton pulse pairs at multiple colors in normal dispersion microresonators
Soliton microcombs are helping to advance the miniaturization of a range of
comb systems. These combs mode lock through the formation of short temporal
pulses in anomalous dispersion resonators. Here, a new microcomb is
demonstrated that mode locks through the formation of pulse pairs in
normal-dispersion coupled-ring resonators. Unlike conventional microcombs,
pulses in this system cannot exist alone, and instead must phase lock in pairs
to form a bright soliton comb. Also, the pulses can form at recurring spectral
windows and the pulses in each pair feature different optical spectra. This
pairwise mode-locking modality extends to higher dimensions and we demonstrate
3-ring systems in which 3 pulses mode lock through alternating pairwise pulse
coupling. The results are demonstrated using the new CMOS-foundry platform that
has not previously produced bright solitons on account of its inherent normal
dispersion. The ability to generate multi-color pulse pairs over multiple rings
is an important new feature for microcombs. It can extend the concept of
all-optical soliton buffers and memories to multiple storage rings that
multiplex pulses with respect to soliton color and that are spatially
addressable. The results also suggest a new platform for the study of quantum
combs and topological photonics
Probing material absorption and optical nonlinearity of integrated photonic materials
Optical microresonators with high quality () factors are essential to a
wide range of integrated photonic devices. Steady efforts have been directed
towards increasing microresonator factors across a variety of platforms.
With success in reducing microfabrication process-related optical loss as a
limitation of , the ultimate attainable , as determined solely by the
constituent microresonator material absorption, has come into focus. Here, we
report measurements of the material-limited factors in several photonic
material platforms. High- microresonators are fabricated from thin films of
SiO, SiN, AlGaAs and TaO. By using
cavity-enhanced photothermal spectroscopy, the material-limited is
determined. The method simultaneously measures the Kerr nonlinearity in each
material and reveals how material nonlinearity and ultimate vary in a
complementary fashion across photonic materials. Besides guiding microresonator
design and material development in four material platforms, the results help
establish performance limits in future photonic integrated systems.Comment: Maodong Gao, Qi-Fan Yang and Qing-Xin Ji contributed equally to this
work. 9 pages, 4 figures, 1 tabl
Engineered zero-dispersion microcombs using CMOS-ready photonics
Normal group velocity dispersion (GVD) microcombs offer high comb line power
and high pumping efficiency compared to bright pulse microcombs. The recent
demonstration of normal GVD microcombs using CMOS-foundry-produced
microresonators is an important step towards scalable production. However, the
chromatic dispersion of CMOS devices is large and impairs generation of
broadband microcombs. Here, we report the development of a microresonator in
which GVD is reduced due to a couple-ring resonator configuration. Operating in
the turnkey self-injection-locking mode, the resonator is hybridly integrated
with a semiconductor laser pump to produce high-power-efficiency combs spanning
a bandwidth of 9.9 nm (1.22 THz) centered at 1560 nm, corresponding to 62 comb
lines. Fast, linear optical sampling of the comb waveform is used to observe
the rich set of near-zero GVD comb behaviors, including soliton molecules,
switching waves (platicons) and their hybrids. Tuning of the 20 GHz repetition
rate by electrical actuation enables servo locking to a microwave reference,
which simultaneously stabilizes the comb repetition rate, offset frequency and
temporal waveform. This hybridly integrated system could be used in coherent
communications or for ultra-stable microwave signal generation by two-point
optical frequency division.Comment: 8 pages, 4 figure
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