15 research outputs found
Broadband near-infrared astronomical spectrometer calibration and on-sky validation with an electro-optic laser frequency comb
The quest for extrasolar planets and their characterisation as well as
studies of fundamental physics on cosmological scales rely on capabilities of
high-resolution astronomical spectroscopy. A central requirement is a precise
wavelength calibration of astronomical spectrographs allowing for extraction of
subtle wavelength shifts from the spectra of stars and quasars. Here, we
present an all-fibre, 400 nm wide near-infrared frequency comb based on
electro-optic modulation with 14.5 GHz comb line spacing. Tests on the
high-resolution, near-infrared spectrometer GIANO-B show a photon-noise limited
calibration precision of <10 cm/s as required for Earth-like planet detection.
Moreover, the presented comb provides detailed insight into particularities of
the spectrograph such as detector inhomogeneities and differential spectrograph
drifts. The system is validated in on-sky observations of a radial velocity
standard star (HD221354) and telluric atmospheric absorption features. The
advantages of the system include simplicity, robustness and turn-key operation,
features that are valuable at the observation sites
Frequency comb up- and down-conversion in a synchronously-driven optical microresonator
Optical frequency combs are key to optical precision measurements. While most
frequency combs operate in the near-infrared regime, many applications require
combs at mid-infrared, visible or even ultra-violet wavelengths. Frequency
combs can be transferred to other wavelengths via nonlinear optical processes,
however, this becomes exceedingly challenging for high-repetition rate
frequency combs. Here, it is demonstrated that a synchronously driven high-Q
microresonator with a second-order optical nonlinearity can efficiently convert
high-repetition rate near-infrared frequency combs to visible, ultra-violet and
mid-infrared wavelengths providing new opportunities for microresonator and
electro-optic combs in applications including molecular sensing, astronomy, and
quantum optics
Ultraviolet astronomical spectrograph calibration with laser frequency combs from nanophotonic waveguides
Astronomical precision spectroscopy underpins searches for life beyond Earth,
direct observation of the expanding Universe and constraining the potential
variability of physical constants across cosmological scales. Laser frequency
combs can provide the critically required accurate and precise calibration to
the astronomical spectrographs. For cosmological studies, extending the
calibration with such astrocombs to the ultraviolet spectral range is highly
desirable, however, strong material dispersion and large spectral separation
from the established infrared laser oscillators have made this exceedingly
challenging. Here, we demonstrate for the first time astronomical spectrograph
calibrations with an astrocomb in the ultraviolet spectral range below 400 nm.
This is accomplished via chip-integrated highly nonlinear photonics in
periodically-poled, nano-fabricated lithium niobate waveguides in conjunction
with a robust infrared electro-optic comb generator, as well as a
chip-integrated microresonator comb. These results demonstrate a viable route
towards astronomical precision spectroscopy in the ultraviolet and may
contribute to unlocking the full potential of next generation ground- and
future space-based astronomical instruments
High repetition rate laser frequency combs for astronomical spectrograph calibration
Astronomical spectroscopy allows detection of exoplanets and their atmospheres, and gives insights into variability of physical constants. Astronomical spectrographs require suitable wavelength reference to provide precise and accurate measurements. Laser frequency combs have been recognised as an invaluable tool in spectrograph calibration. This thesis reports on the development and on-site test of two laser frequency combs operating in the near-infrared wavelength range. Both systems, the electro-optic frequency comb and Kerr frequency comb, are based on technologies providing directly high repetition rate (>10 GHz) operation and a calibration precision at the level of tens of cm/s. Furthermore, a novel technique for frequency comb generation in the visible wavelength range is demonstrated, which relies on triple-sum frequency generation in a nonlinear optical waveguide. This thesis contributes to the development of astronomical spectroscopy by offering perspectives for the improvement of existing and future extreme precision astronomical spectrographs
Photonic chip-based resonant supercontinuum via pulse-driven Kerr microresonator solitons
Supercontinuum generation in optical fibers is one of the most dramatic nonlinear effects discovered, allowing short pulses to be converted into multi-octave spanning coherent spectra. However, generating supercontinua that are both coherent and broadband requires pulses that are simultaneously ultrashort with high peak power. This results in a reducing efficiency with increasing pulse repetition rate, that has hindered supercontinua at microwave line spacing, i.e. 10s of GHz. Soliton microcombs by contrast, can generate octave-spanning spectra, but with good conversion efficiency only at vastly higher repetition rates in the 100s of GHz. Here, we bridge this efficiency gap with resonant supercontinuum, allowing supercontinuum generation using input pulses with an ultra-low 6 picojoule energy, and duration of 1 picosecond, 10-fold longer than what is typical. By applying synchronous pulse-driving to a dispersion-engineered, low-loss SiN photonic chip microresonator, we generate dissipative Kerr solitons with a strong dispersive wave, both bound to the input pulse. This creates a smooth, flattened 2,200 line frequency comb, with an electronically detectable repetition rate of 28 GHz, constituting the largest bandwidth-line-count product for any microcomb generated to date. Strikingly, we observe that solitons exist in a weakly bound state with the input pulse, stabilizing their repetition rate, but simultaneously allowing noise transfer from one to the other to be suppressed even for offset frequencies 100 times lower than the linear cavity decay rate. We demonstrate that this nonlinear filtering can be enhanced by pulse-driving asynchronously, in order to preserve the coherence of the comb. Taken together, our work establishes resonant supercontinuum as a promising route to broadband and coherent spectra
Photonic chip-based resonant supercontinuum via pulse-driven Kerr microresonator solitons
Supercontinuum generation in optical fibers is one of the most dramatic nonlinear effects discovered, allowing short pulses to be converted into multi-octave spanning coherent spectra. However, generating supercontinua that are both coherent and broadband requires pulses that are simultaneously ultrashort with high peak power. This results in a reducing efficiency with increasing pulse repetition rate, that has hindered supercontinua at microwave line spacing, i.e. 10s of GHz. Soliton microcombs by contrast, can generate octave-spanning spectra, but with good conversion efficiency only at vastly higher repetition rates in the 100s of GHz. Here, we bridge this efficiency gap with resonant supercontinuum, allowing supercontinuum generation using input pulses with an ultra-low 6 picojoule energy, and duration of 1 picosecond, 10-fold longer than what is typical. By applying synchronous pulse-driving to a dispersion-engineered, low-loss SiN photonic chip microresonator, we generate dissipative Kerr solitons with a strong dispersive wave, both bound to the input pulse. This creates a smooth, flattened 2,200 line frequency comb, with an electronically detectable repetition rate of 28 GHz, constituting the largest bandwidth-line-count product for any microcomb generated to date. Strikingly, we observe that solitons exist in a weakly bound state with the input pulse, stabilizing their repetition rate, but simultaneously allowing noise transfer from one to the other to be suppressed even for offset frequencies 100 times lower than the linear cavity decay rate. We demonstrate that this nonlinear filtering can be enhanced by pulse-driving asynchronously, in order to preserve the coherence of the comb. Taken together, our work establishes resonant supercontinuum as a promising route to broadband and coherent spectra
Broadband Efficient Soliton Microcombs in Pulse-Driven Photonic Microresonators
Broadband single-soliton based frequency combs, with a detectable repetition rate of 28 GHz, are efficiently generated through pulse-driving of a chip-based Si3N4 microresonator. We observe an influence of the pulse-driving rate on the comb mode linewidth. (C) 2019 The Author(s