23 research outputs found
Generation of platicons and frequency combs in optical microresonators with normal GVD by modulated pump
We demonstrate that flat-topped dissipative solitonic pulses, platicons, and
corresponding frequency combs can be excited in optical microresonators with
normal group velocity dispersion using either amplitude modulation of the pump
or bichromatic pump. Soft excitation may occur in particular frequency range if
modulation depth is large enough and modulation frequency is close to the free
spectral range of the microresonator.Comment: 10 pages, 4 figures, to appear in EP
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
Slice-Less Optical Arbitrary Waveform Measurement (OAWM) in a Bandwidth of More than 600 GHz Using Soliton Microcombs
We propose and demonstrate a novel scheme for optical arbitrary waveform
measurement (OAWM) that exploits chip-scale Kerr soliton combs as highly
scalable multiwavelength local oscillators (LO) for ultra-broadband full-field
waveform acquisition. In contrast to earlier concepts, our approach does not
require any optical slicing filters and thus lends itself to efficient
implementation on state-of-the-art high-index-contrast integration platforms
such as silicon photonics. The scheme allows to measure truly arbitrary
waveforms with high accuracy, based on a dedicated system model which is
calibrated by means of a femtosecond laser with known pulse shape. We
demonstrated the viability of the approach in a proof-of-concept experiment by
capturing an optical waveform that contains multiple 16 QAM and 64 QAM
wavelength-division multiplexed (WDM) data signals with symbol rates of up to
80 GBd, reaching overall line rates of up to 1.92 Tbit/s within an optical
acquisition bandwidth of 610 GHz. To the best of our knowledge, this is the
highest bandwidth that has so far been demonstrated in an OAWM experiment
Lithium tantalate electro-optical photonic integrated circuits for high volume manufacturing
Photonic integrated circuits based on Lithium Niobate have demonstrated the
vast capabilities afforded by material with a high Pockels coefficient,
allowing linear and high-speed modulators operating at CMOS voltage levels for
applications ranging from data-center communications and photonic accelerators
for AI. However despite major progress, the industrial adoption of this
technology is compounded by the high cost per wafer. Here we overcome this
challenge and demonstrate a photonic platform that satisfies the dichotomy of
allowing scalable manufacturing at low cost, while at the same time exhibiting
equal, and superior properties to those of Lithium Niobate. We demonstrate that
it is possible to manufacture low loss photonic integrated circuits using
Lithium Tantalate, a material that is already commercially adopted for acoustic
filters in 5G and 6G. We show that LiTaO3 posses equally attractive optical
properties and can be etched with high precision and negligible residues using
DUV lithography, diamond like carbon (DLC) as a hard mask and alkaline wet
etching. Using this approach we demonstrate microresonators with an intrinsic
cavity linewidth of 26.8 MHz, corresponding to a linear loss of 5.6 dB/m and
demonstrate a Mach Zehnder modulator with Vpi L = 4.2 V cm half-wave voltage
length product. In comparison to Lithium Niobate, the photonic integrated
circuits based on LiTaO3 exhibit a much lower birefringence, allowing
high-density circuits and broadband operation over all telecommunication bands
(O to L band), exhibit higher photorefractive damage threshold, and lower
microwave loss tangent. Moreover, we show that the platform supports generation
of soliton microcombs in X-Cut LiTaO3 racetrack microresonator with
electronically detectable repetition rate, i.e. 30.1 GHz.Comment: 8 pages, 4 figure