Stabilized dual optical frequency transfer is demonstrated through wavelength- division or polarization multiplexing in a 184-meter long polarization-maintaining fiber link. The latter is stabilized at a primary frequency in the telecom C-band using the established Doppler cancellation technique. Simultaneously, a secondary optical frequency is transferred in the same fiber. Out-of-loop characterization demonstrates an indirect Doppler cancellation for the secondary optical frequency. Compared to an unstabilized link, at 1000 seconds integration time we measure an 11.5 dB stability improvement for wavelength-division multiplexing and a 16 dB improvement for polarization multiplexing. Taking advantage of a stabilized link to distribute other wavelengths is useful for applications in frequency metrology. As an example, we are using a cavity-stabilized 1560 nm laser to stabilize the fiber link while a 1556.2 nm two-photon rubidium clock laser is being distributed. (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Mode-locked lasers, and in particular solid-state femtosecond lasers, are oscillators with a unique physics capable to exhibit extremely low-phase noise of the emitted pulse train. Here we report ultra-low phase noise microwave generation with a self-referenced, fully-stabilized mode-locked femtosecond laser. The system involves a 395-MHz repetition rate 1560nm laser which is self-referenced and whose repetition rate is locked to a cavity-stabilized continuous-wave laser. The selfreferencing is achieved with a f-3f nonlinear interferometer realized in a silicon nitride highly-nonlinear waveguide. Prior to optical-to-electrical conversion for X-band microwave generation, the 395-MHz repetition rate of the mode-locked laser pulse train is multiplied in a fiber interleaver to 3.16 GHz. A high-power handling photodiode converts the optical pulse train to an electrical frequency comb with 3.16 GHz frequency spacing. Finally, the 9.5-GHz harmonics is bandpassfiltered and phase noise measurements have shown a record-low phase noise floor of -175 dBc/Hz at 1-MHz offset frequency.

European Space Agency (ESA) considers Mode-Locked Semi-Conductor Laser (MLSCL) technology as a promising candidate for applications in precision optical metrology spaceborne systems such as High Accuracy Absolute Long Distance Measurement (HAALDM). Very challenging performance requirements should be met for these applications: pulse duration <; 1ps, pulse repetition frequency (PRF) of 1-3 GHz, PRF stability <; 5·10 -9 , PRF tunability > 20MHz, average optical output power > 200 mW, pulse energy > 200pJ, high spatial beam quality (M 2 <; 2.5) in addition to the space application requirements on launch vibrations, volume, weight, power consumption and efficiency. Previously, we have realized two types of passively mode-locked (ML) multiple section edge emitting lasers to address these challenging targets: (i) very long (13.5mm) monolithic tapered laser [1], and (ii) inverse bow-tie external cavity (EC) laser [2]. Both lasers are designed using the model from [3] and produce mode-locked pulses of 70-90pJ energy without amplifier stages. In this communication we report on the design, fabrication and testing of a novel monolithic tapered laser achieving pulse energy up to 200pJ from a solitary chip (Fig.1, panel (a)). While the epitaxial structure is the same as reported in [2] the tapered laser structure has now different cavity sections: two absorber sections, a tuning section and a gain section. The last one consists of the linear and the tapered waveguide parts and comprises beam spoilers in between the two parts.

Recent detection of gravitational waves (GWs) by ground-based instruments and the success of the LISA pathfinder mission motivate the swift implementation of the Laser Interferometer Space Antenna (LISA) mission. LISA aims at the detection of low frequency GWs in space with optical interferometry among three satellites flying in a triangular formation with 2.5 million km arm length. Power stability, spectral purity and frequency stability of the lasers are extremely important for achieving the desirable instrument sensitivity. Here we present a prototype of a laser system demonstrating performance which is already close to the mission requirements at high offset frequencies. The prototype is based on technologies that are compatible with future space qualification.

To the best of our knowledge, we demonstrate the first mode-locked semiconductor laser reaching 201pJ picosecond pulses without amplifier at low repetition frequency of 2.89GHz, with a very-long (13.5mm) multi-sections tapered laser diode structure, required by European Space Agency for inter-satellite long distance measurements.

The quest for extrasolar planets and their characterization 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-fiber, 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 cms 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.

Synchronous-driving of nonlinear optical microresonator offers robust, deterministic and ultra- efficient generation of ultra-short temporal soliton pulses as well as high-repetition rate frequency combs. The soliton pulses are all-optically controlled and provide resolvable lines for astronomical spectrometer calibration or optical telecommunications.

We report on multi-section inverse bow-tie laser producing mode-locked pulses of 90 pJ energy and 6.5 ps width (895 fs after compression) at 1.3 GHz pulse repetition frequency (PRF) and consuming 2.9 W of electric power. The laser operates in an 80 mm long external cavity. By translation of the output coupling mirror, the PRF was continuously tuned over 37 MHz range without additional adjustments. Active stabilization with a phase lock loop actuating on the driving current has allowed us to reach the PRF relative stability at a 2.10-10 level on 10 s intervals, as required by the European Space Agency (ESA) for inter-satellite long distance measurements.

We report on multi-section inverse bow-tie laser producing mode-locked pulses of 90 pJ energy and 6.5 ps width (895 fs after compression) at 1.3 GHz pulse repetition frequency (PRF) and consuming 2.9 W of electric power. The laser operates in an 80 mm long external cavity. By translation of the output coupling mirror, the PRF was continuously tuned over 37 MHz range without additional adjustments. Active stabilization with a phase lock loop actuating on the driving current has allowed us to reach the PRF relative stability at a 2·10-10 level on 10 s intervals, as required by the European Space Agency (ESA) for inter-satellite long distance measurements.

Absolute calibration of an astronomical spectrometer is demonstrated via a microresonator-soliton frequency comb. This novel approach achieves a precision of 25 cm/s without spectral filtering and is relevant to searches for Earth-like planets.

Two commercial femtosecond laser sources have been used to implement a dual-comb spectrometer tuneable across a spectral range from 1.5 to 2.2 μm. The optical linewidth of the comb modes was characterized for different time scales in order to estimate the achievable spectral resolution for an optimal acquisition time. The transmission spectra of three different gas samples were recorded, demonstrating good agreement with reference data. Frequency axis calibration was provided via the parallel monitoring of a reference sample. This technique allows an accurate calibration of the frequency axis of the spectrometer, with no need for stabilization or optical referencing of the frequency combs. Our set-up represents a good compromise for a compact and versatile dual-comb spectrometer based on commercially available parts with possible applications in trace-gas monitoring, remote sensing and spectroscopy of short-lived processes.

A robust optical frequency comb is realised with an Origami-10 mode-locked femtosecond laser from Onefive GmbH generating a 100 MHz pulse train at a centre wavelength of 1047 nm. The carrier-envelope offset frequency has been stabilised to a record level contributing to relative fluctuations of the optical carrier frequency of 1.1 x 10(-18) at 1 s and averaging down to the 10(-22) level at 10 000 s. Cycle-slip free carrier-envelope offset frequency stabilisation has been routinely achieved over 10 h. Ultra-low relative intensity noise has been measured as well and makes such a system very attractive for demanding applications where low noise and high reliability are requested.

We investigate the required pulse duration for coherent supercontinuum generation for CEO detection in the 1-µm and 1.5-µm spectral regime. We demonstrate the first self-referenceable frequency comb from a gigahertz diode-pumped solid state laser.