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Numerous modern technologies are reliant on the low-phase noise and exquisite timing stability of microwave signals. Substantial progress has been made in the field of microwave photonics, whereby low-noise microwave signals are generated by the down-conversion of ultrastable optical references using a frequency comb 1 – 3 . Such systems, however, are constructed with bulk or fibre optics and are difficult to further reduce in size and power consumption. In this work we address this challenge by leveraging advances in integrated photonics to demonstrate low-noise microwave generation via two-point optical frequency division 4 , 5 . Narrow-linewidth self-injection-locked integrated lasers 6 , 7 are stabilized to a miniature Fabry–Pérot cavity 8 , and the frequency gap between the lasers is divided with an efficient dark soliton frequency comb 9 . The stabilized output of the microcomb is photodetected to produce a microwave signal at 20 GHz with phase noise of −96 dBc Hz −1 at 100 Hz offset frequency that decreases to −135 dBc Hz −1 at 10 kHz offset—values that are unprecedented for an integrated photonic system. All photonic components can be heterogeneously integrated on a single chip, providing a significant advance for the application of photonics to high-precision navigation, communication and timing systems. We leverage advances in integrated photonics to generate low-noise microwaves with an optical frequency division architecture that can be low power and chip integrated.

Gyroscopes merit an undeniable role in inertial navigation systems, geodesy and seismology. By employing the optical Sagnac effect, ring laser gyroscopes provide exceptionally accurate measurements of even ultraslow angular velocity with a resolution up to 10−11 rad/s. With the recent advancement of ultrafast fibre lasers and, particularly, enabling effective bidirectional generation, their applications have been expanded to the areas of dual-comb spectroscopy and gyroscopy. Exceptional compactness, maintenance-free operation and rather low cost make ultrafast fibre lasers attractive for sensing applications. Remarkably, laser gyroscope operation in the ultrashort pulse generation regime presents a promising approach for eliminating sensing limitations caused by the synchronisation of counter-propagating channels, the most critical of which is frequency lock-in. In this work, we overview the fundamentals of gyroscopic sensing and ultrafast fibre lasers to bridge the gap between tools development and their real-world applications. This article provides a historical outline, highlights the most recent advancements and discusses perspectives for the expanding field of ultrafast fibre laser gyroscopes. We acknowledge the bottlenecks and deficiencies of the presented ultrafast laser gyroscope concepts due to intrinsic physical effects or currently available measurement methodology. Finally, the current work outlines solutions for further ultrafast laser technology development to translate to future commercial gyroscopes.

Dual optical frequency combs have been a recurrent case of study over the last decade due to their wide use in a variety of metrology applications. Utilizing a single cavity laser to generate a dual comb reduces system complexity and facilitates suppression of common noise. However, a dual-comb regime in single cavity lasers tends to be more unstable and difficult to achieve. Therefore, having a better understanding about the way they are generated could improve and automate their generation and control. In this paper, we investigate the build-up dynamics and collision of dual comb in a polarization-multiplexing ring-cavity fiber laser using DFT (Dispersive Fourier Transform) method. We observe a bunch of meta-stable short-lived mode-locking states before the laser entered the dual-comb mode-locking state. The energy level of this short-lived initial pulses determines its evolution. If it decreases too much, the pulse will eventually collapse while if it stays above certain level, it will be successfully generated. The results presented in this paper increase the understanding of dual-comb generation inside a single cavity laser and may contribute in future attempts to increase the stabilization of this regime.

Real-time observation of the emergence of coherent structures from noise via instabilities is of particular interest across disciplines ranging from biology to astrophysics. In the context of photonics, ultrafast fibre lasers provide an ideal test-bed for experimental observation of dynamical instabilities and generation of coherent structures of ultrashort pulses. Here we present experimentally obtained switch-on dynamics of counter-propagating ultrashort pulses in a bidirectional mode-locked fibre laser with delayed pulse formation via Q-switched and modulation instabilities, pronounced central wavelength drift, with the multiple-pulse formation. We define a localisation parameter using the round-trip resolved autocorrelation function to quantify the extent of the pulse formation, indicating an energy interchange between coherent features and background radiation. Furthermore, we report the formation of synchronised and unsynchronised dispersion waves. Our results reveal the complexity of the establishment of coherent features and their interaction with background radiation, contributing further towards the understanding of nonlinear systems in general. Emergent coherence in noisy, nonlinear systems of broad scientific relevance can be examined in real-time in optical analogues. Here, the complex dynamics of counter-propagating coherent pulses is examined, revealing how energy is exchanged between both channels and background radiation.

We have studied the ultrafast saturation behavior of a high-density well-aligned single-walled carbon nanotubes saturable absorber (HDWA-SWCNT SA), obtained by a high-pressure and high-temperature treatment of commercially available single-wall carbon nanotubes (SWCNTs) and related it to femtosecond erbium-doped fiber laser performance. We have observed the polarization dependence of a nonlinear optical saturation, along with a low saturation energy level of <1 fJ, limited to the detector threshold used, and the ultrafast response time of <250 fs, while the modulation depth was approximately 12%. We have obtained the generation of ultrashort stretched pulses with a low mode-locking launching threshold of ~100 mW and an average output power of 12.5 mW in an erbium-doped ring laser with the hybrid mode-locking of a VDVA-SWNT SA in combination with the effects of nonlinear polarization evolution. Dechirped pulses with a duration of 180 fs were generated, with a repetition rate of about 42.22 MHz. The average output power standard deviation was about 0.06% RMS during 3 h of measurement.

Almost all inertial navigation systems rely on optical gyroscopes, operating on the Sagnac effect. Laser gyroscopes demonstrate high precision in demanding applications such as seismology and geodesy. Passive optical gyroscopes, typically fiber‐optic gyroscopes (FOGs), are of particular interest due to the lack of the “lock‐in” effect, which is the most detrimental effect in active laser systems. Still, the current data acquisition rate of modern FOGs cannot satisfy emerging applications, particularly for autonomous navigation. Herein, a novel interferometric FOG, based on the measurements of ultrashort pulse phase via the dispersive Fourier transformation, is presented, demonstrating the highest up‐to‐date acquisition rate of 15 MHz. This setup is insensitive to the timing jitter and the fluctuations of the carrier‐envelope phase of the pulses. The single‐shot resolution of the phase retrieval is 7.3 mrad, which corresponds to a time shift of 8.7 attoseconds. As a confirmation of the high‐speed performance, movements of a stepper motor are recorded with an angular velocity resolution of 0.33 mdeg s−1 and a bias instability of 0.06 deg h−1 at acquisition time of 17.07 μs. The proposed method can facilitate various phase measurements at a high repetition rate and is not limited only to gyroscopic applications. The current data acquisition rate of modern optical gyroscopes cannot satisfy emerging applications, particularly autonomous navigation. The authors present a novel interferometric fiber‐optic measuring the ultrashort pulse phase via the dispersive Fourier transformation. The system demonstrates the single‐shot phase retrieval resolution of 7.3 mrad or an angular velocity resolution of 0.33 mdeg s−1 at a 15 MHz acquisition rate.

A hybrid optoelectronic synthesizer is developed that combines simplified optical frequency division with direct digital synthesis to generate tunable, low-phase-noise microwaves across the X-band. This approach also achieves high frequency stability while reducing the size, weight and power demands, paving the way for chip-scale photonic microwave sources.

Interferometric Fiber‐Optic GyroscopesOptical measurements of rotation velocities traditionally rely on highly averaged Sagnac effect interrogation. In manuscript number 2200092, Igor Kudelin, Srikanth Sugavanam, and Maria Chernysheva enhance the possibilities of direct rotation detection by combining the benefits of the Mach‐Zehnder interferometer and dispersive Fourier transform measurement technique. Such an approach allows achieving a new level of angular rotation resolution as low as 0.33 mdeg s−1 at unprecedent acquisition rates beyond tens of MHz.

Modern applications are constantly pushing the limits of current technologies, requiring further improvements in their precision. The advances in laser development significantly contribute to the achievements of modern technologies. One of the niches of precision technologies is gyroscopic measurements, where laser-based gyroscopes deliver unparalleled accuracy. Nonetheless, laser gyroscopes are subjected to the general limitation as 'lock-in' effect, which restricts the lowest measurable angular velocity. The usage of pulsed laser sources, such as mode-locked lasers, can mitigate this deleterious effect and benefit the laser gyroscope development. The extensive studying of ultrafast lasers over the last few decades significantly improved their performance, extending their applications to extremely precise measurements such as optical clocks and telescope calibration. However, the usage of ultrafast lasers for the detection of angular rotations is still rudimentary and requires further studies. In this manuscript, our goal is to contribute to the scientific achievements in the area of ultrashort pulses interferometry and, in particular, gyroscopic applications. We aim to deliver novel approaches for phase measurements at high data frequencies by using the recent advances in fast electronics and ultrafast measurement techniques. Firstly, we study bidirectional mode-locked fibre laser and its applicability for the detection of angular movements. Indicating the main obstacles to achieve continuous reliable results, in the following chapter we propose another interferometric setup, which provides the measurements of the pulse-to-pulse phase drift and can be used to characterise the phase noise of a pulse train or being exploited for interferometry. Finally, we demonstrate a passive gyro setup based on interferometric measurements, which inherits all the benefits of the usage of ultrashort pulses, while the phase noises of the laser source are significantly mitigated. We conclude that ultrashort pulses can benefit many phase-based applications, which require high resolution and high data rates, including but not limited to gyroscopic measurements.

Numerous modern technologies are reliant on the low-phase noise and exquisite timing stability of microwave signals. Substantial progress has been made in the field of microwave photonics, whereby low-noise microwave signals are generated by the down-conversion of ultrastable optical references using a frequency comb13. Such systems, however, are constructed with bulk or fibre optics and are difficult to further reduce in size and power consumption. In this work we address this challenge by leveraging advances in integrated photonics to demonstrate low-noise microwave generation via two-point optical frequency division4,5. Narrow-linewidth self-injection-locked integrated lasers6,7 are stabilized to a miniature Fabry-Perot cavity8, and the frequency gap between the lasers is divided with an efficient dark soliton frequency comb9. The stabilized output of the microcomb is photodetected to produce a microwave signal at 20 GHz with phase noise of-96 dBc Hz1 at 100 Hz offset frequency that decreases to -135 dBc Hz1 at 10 kHz offset-values that are unprecedented for an integrated photonic system. All photonic components can be heterogeneously integrated on a single chip, providing a significant advance for the application of photonics to high-precision navigation, communication and timing systems.