40 research outputs found
On-chip optical parametric oscillation into the visible: generating red, orange, yellow, and green from a near-infrared pump
Optical parametric oscillation (OPO) in a microresonator is promising as an
efficient and scalable approach to on-chip coherent visible light generation.
However, so far only red light at < 420 THz (near the edge of the visible band)
has been reported. In this work, we demonstrate on-chip OPO covering > 130 THz
of the visible spectrum, including red, orange, yellow, and green wavelengths.
In particular, using a pump laser that is scanned 5 THz in the near-infrared
from 386 THz to 391 THz, the signal is tuned from the near-infrared at 395 THz
to the visible at 528 THz, while the idler is tuned from the near-infrared at
378 THz to the infrared at 254 THz. The widest signal-idler separation we
demonstrate of 274 THz corresponds to more than an octave span and is the
widest demonstrated for a nanophotonic OPO to date. Our work is a clear
demonstration of how nonlinear nanophotonics can transform light from readily
accessible compact near-infrared lasers to targeted visible wavelengths of
interest, which is crucial for field-level deployment of spectroscopy and
metrology systems.Comment: 6 pages, 5 figure
A universal frequency engineering tool for microcavity nonlinear optics: multiple selective mode splitting of whispering-gallery resonances
Whispering-gallery microcavities have been used to realize a variety of
efficient parametric nonlinear optical processes through the enhanced
light-matter interaction brought about by supporting multiple high quality
factor and small modal volume resonances. Critical to such studies is the
ability to control the relative frequencies of the cavity modes, so that
frequency matching is achieved to satisfy energy conservation. Typically this
is done by tailoring the resonator cross-section. Doing so modifies the
frequencies of all of the cavity modes, that is, the global dispersion profile,
which may be undesired, for example, in introducing competing nonlinear
processes.Here, we demonstrate a frequency engineering tool, termed multiple
selective mode splitting (MSMS), that is independent of the global dispersion
and instead allows targeted and independent control of the frequencies of
multiple cavity modes. In particular, we show controllable frequency shifts up
to 0.8 nm, independent control of the splitting of up to five cavity modes with
optical quality factors , and strongly suppressed frequency
shifts for untargeted modes. The MSMS technique can be broadly applied to a
wide variety of nonlinear optical processes across different material
platforms, and can be used to both selectively enhance processes of interestand
suppress competing unwanted processes.Comment: 13 pages, 8 figure
Scalable and Robust Beam Shaping Using Apodized Fish-bone Grating Couplers
Efficient power coupling between on-chip guided and free-space optical modes
requires precision spatial mode matching with apodized grating couplers. Yet,
grating apodizations are often limited by the minimum feature size of the
fabrication approach. This is especially challenging when small feature sizes
are required to fabricate gratings at short wavelengths or to achieve weakly
scattered light for large-area gratings. Here, we demonstrate a fish-bone
grating coupler for precision beam shaping and the generation of
millimeter-scale beams at 461 nm wavelength. Our design decouples the minimum
feature size from the minimum achievable optical scattering strength, allowing
smooth turn-on and continuous control of the emission. Our approach is
compatible with commercial foundry photolithography and has reduced sensitivity
to both the resolution and the variability of the fabrication approach compared
to subwavelength meta-gratings, which often require electron beam lithography.Comment: 10 pages, 6 figure
Sub-Doppler spectroscopy of quantum systems through nanophotonic spectral translation of electro-optic light
An outstanding challenge for deployable quantum technologies is the
availability of high-resolution laser spectroscopy at the specific wavelengths
of ultranarrow transitions in atomic and solid-state quantum systems. Here, we
demonstrate a powerful spectroscopic tool that synergistically combines high
resolution with flexible wavelength access, by showing that nonlinear
nanophotonics can be readily pumped with electro-optic frequency combs to
enable highly coherent spectral translation with essentially no efficiency
loss. Third-order (\c{hi}(3)) optical parametric oscillation in a silicon
nitride microring enables nearly a million optical frequency comb pump teeth to
be translated onto signal and idler beams; while the comb tooth spacing and
bandwidth are adjustable through electro-optic control, the signal and idler
carrier frequencies are widely tuneable through dispersion engineering. We then
demonstrate the application of these devices to quantum systems, by performing
sub-Doppler spectroscopy of the hyperfine transitions of a Cs atomic vapor with
our electro-optically-driven Kerr nonlinear light source. The generality,
robustness, and agility of this approach as well as its compatibility with
photonic integration are expected to lead to its widespread applications in
areas such as quantum sensing, telecommunications, and atomic clocks.Comment: 17 pages, 5 figure
Stably accessing octave-spanning microresonator frequency combs in the soliton regime
Microresonator frequency combs can be an enabling technology for optical
frequency synthesis and timekeeping in low size, weight, and power
architectures. Such systems require comb operation in low-noise, phase-coherent
states such as solitons, with broad spectral bandwidths (e.g., octave-spanning)
for self-referencing to detect the carrier-envelope offset frequency. However,
stably accessing such states is complicated by thermo-optic dispersion. For
example, in the Si3N4 platform, precisely dispersion-engineered structures can
support broadband operation, but microsecond thermal time constants have
necessitated fast pump power or frequency control to stabilize the solitons. In
contrast, here we consider how broadband soliton states can be accessed with
simple pump laser frequency tuning, at a rate much slower than the thermal
dynamics. We demonstrate octave-spanning soliton frequency combs in Si3N4
microresonators, including the generation of a multi-soliton state with a pump
power near 40 mW and a single-soliton state with a pump power near 120 mW. We
also develop a simplified two-step analysis to explain how these states are
accessed in a thermally stable way without fast control of the pump laser, and
outline the required thermal properties for such operation. Our model agrees
with experimental results as well as numerical simulations based on a
Lugiato-Lefever equation that incorporates thermo-optic dispersion. Moreover,
it also explains an experimental observation that a member of an adjacent mode
family on the red-detuned side of the pump mode can mitigate the thermal
requirements for accessing soliton states