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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - High-Frame-Rate Single-Shot Spectrum Measurement for Ultrafast Optical Pulses Based on Optical Signal Processing
摘要： The pulse-by-pulse single-shot spectrum measurement for high-repetition rate optical pulses with femtosecond or picosecond pulse width is important for capturing non-repetitive and rare phenomena of substances. Conventional optical spectrum analyzers cannot acquire the spectrum for each pulse at high-repetition rate without missing due to the low processing speed. Several high-speed optical signal processing techniques can help to acquire pulse-by-pulse single-shot spectrum. The high-speed spectrum measurement using a fiber chromatic dispersion-based time stretch dispersive Fourier Transform (TS-DFT) technique is a powerful tool for such measurements. In this paper, we present a record pulse-by-pulse single-shot spectrum measurement for 1 GHz repetition-rate optical pulses with a less than 67-pm spectral resolution based on the TS-DFT technique.
关键词： time stretch dispersive Fourier Transform,single-shot spectrum measurement,optical signal processing
更新于2025-09-23 15:23:52
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Generation and pulsating behaviors of loosely bound solitons in a passively mode-locked fiber laser
摘要： We demonstrate the experimental observation of loosely bound solitons and pulsations in a passively mode-locked ?ber laser. The soliton amount inside one soliton bunch typically increases with the increment of pump power, while the average pulse-to-pulse separation in the regime of hundreds of picoseconds decreases in principle accordingly. Besides, by employing the real-time measurement based on the dispersive Fourier-transform technique, we ?nd that some solitons in a single bunch are experiencing a simultaneous pulsating process with a period corresponding to 100 times longer than the cavity round-trip time. The experimental results can be bene?cial for better understanding the formation of multiple solitons and pulsating solitons and enriching the nonlinear phenomena in complex soliton systems.
关键词： dispersive Fourier-transform technique,pulsating solitons,loosely bound solitons,passively mode-locked ?ber laser
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Buildup of Noise-Like Pulses in Ultrafast Fiber Lasers
摘要： Noise-like pulses (NLP) - the emission of sub-nanosecond incoherent pulses in ultrafast lasers - are a topic of widespread attention, owing to their fundamental and applied interest [1]. Their existence seems paradoxical, combining the high temporal localization of circulating pulses akin to mode-locking, with a fundamental instability that entails large fluctuations [2]. NLPs can be considered as incoherent dissipative solitons [3]. It is therefore of considerable interest to investigate the self-emergence of these pulses in the laser. We undertake this study experimentally using the time-stretch dispersive Fourier transform (DFT), recording the pulse spectral and temporal information in real time over successive cavity roundtrips [4]. The buildup dynamics of noise-like pulses in both anomalous and normal-dispersion fiber lasers are compared, revealing markedly different stages and timescales in the evolution process.
关键词： anomalous dispersion,normal dispersion,Noise-like pulses,ultrafast fiber lasers,dispersive Fourier transform
更新于2025-09-16 10:30:52
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Route from single-pulse to multi-pulse states in a mid-infrared soliton fiber laser
摘要： State-of-the-art ultrafast mid-IR ?ber lasers deliver optical solitons with durations of several hundred femtoseconds. The Er- or Ho-doped ?uoride gain ?bers generally used in these lasers have strong anomalous dispersion at ～3 μm, which generally forces them to operate in the soliton regime. Here we report that a pulse-energy clamping e?ect, caused by the buildup of intracavity nonlinearities, limits the shortest obtainable pulse durations in these mid-infrared soliton ?ber lasers. Excessive intra-cavity energy results in soliton instability, collapse and fragmentation into a variety of stable multi-pulse states, including phase-locked soliton molecules and harmonically mode-locked states. We report that the spectral evolution of the mid-IR laser pulses can be recorded between roundtrips through stretching their second-harmonic signal in a 25-km-length of single-mode ?ber. Using a modi?ed dispersive Fourier transform set-up, we were able to perform for the ?rst time spectro-temporal measurements of mid-IR laser pulses both in the pulsed state and during pulse collapse and fragmentation. The results provide insight into the complex nonlinear dynamics of mid-IR soliton ?ber lasers and open up new opportunities for obtaining a variety of stable multi-pulse mode-locked states at mid-IR wavelengths.
关键词： dispersive Fourier transform,soliton instability,multi-pulse states,pulse-energy clamping,mid-IR soliton ?ber lasers
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Direct Observation of Intracavity Pulse Dynamics in All-Normal Dispersion All-Fiber Oscillator
摘要： Ultrafast science and technology depend strongly on the development of novel ultrafast sources, thus good understanding of nonlinear phenomena in such systems is of essence. In this paper, we present the experimental observation and theoretical analysis of various pulse dynamics in all-normal dispersion cavity producing dissipative soliton pulses. We report the results of an extensive study regarding the Stimulated Raman Scattering (SRS) process, which creates a main upper limitation for the pulse energy achievable from all-normal dispersion fiber oscillators. We report the measurements of real-time, single shot spectra registered using Dispersive Fourier Transform (DFT) technique together with measured averaged spectral phase of the pulses generated from an all-PM-fiber oscillator mode-locked with Nonlinear Optical Loop Mirror (NOLM). It is found that NOLM parameters directly influenced the pulse stability and dynamics. The Yb-doped fiber was used as an active medium and Dissipative Soliton (DS) pulses centered at 1030 nm were generated together with Stokes radiation shifted by 440 cm-1 (centered approximately at 1078 nm) produced in SRS process. The light generated in SRS process was suppressed from round-trip to round-trip by a narrow pass-band spectral filter centered at 1030 nm placed inside the laser cavity. We present the broad experimental study of ultrashort pulse dynamics with strong presence of SRS process. Spectral intensity correlation maps were calculated to describe how the SRS process disturbs the ultrashort pulse during propagation in the cavity (Fig. 1). The intensities of longer wavelengths (1040 – 1050 nm) in the pulse spectrum were destabilized due to the SRS process. In normal dispersion fiber Stokes SRS components have higher group velocity than the pulse spectral components. For positively chirped pulse SRS affects only the leading edge of the pulse which is manifested as negative correlation (Fig. 1(c)). The phenomena of repetitive partial dissipative soliton explosions and bistability of the pulse operation in an all-PM-fiber all-normal dispersion oscillator cavity were investigated as well. The clear signature of bistable operation was the hysteresis of the laser pulse power versus input pump power. Furthermore, we registered significant differences between the measured pulses spectral phases for each case. Another set of measurements was performed to analyze the pulse self-starting dynamics. We present the experimental study and numerical simulations of DS pulse dynamics in an all-normal dispersion all-fiber cavity. The numerical simulations were performed using the standard split-step Fourier-transform method employing the multi-vibrational model of SRS. DS lasers are important pulse sources and an effective platform to investigate the pulse dynamics and nonlinear processes inside the all-fiber cavities.
关键词： spectral intensity correlation maps,Yb-doped fiber,dissipative soliton pulses,Dispersive Fourier Transform,split-step Fourier-transform method,Nonlinear Optical Loop Mirror,Stimulated Raman Scattering,ultrafast science
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Dispersive Fourier Transform Based Single-Shot CEP Drift Measurement at Arbitrary Repetition Rate
摘要： In recent years attosecond science motivated the development of laser systems, which provide millijoule energy level few-cycle pulses. These experiments rely on a field with stable amplitude and carrier envelope phase (CEP) to provide reproducible results [1]. As a consequence, diagnostic devices, which are capable of single-shot CEP measurement and pulse tagging, became a must-have equipment in today’s laser systems. The self-referenced interferometry such as f-to-2f [2] are one of the most typical way to characterize the shift of the CEP in a single-shot manner. The highest achievable recording rate is mostly limited by the measurement times of the optical spectroscopes, which can only reach 10 kHz even with fast detector array. Dispersive Fourier Transform (DFT) [3,4] can be used to bypass this limitation, so single-shot recordings of the output signal of an f-to-2f interferometer becomes possible even at high repetition rates. The method depends on an optical element with enough dispersion to stretch to pulse duration up to the nanosecond range. Therefore, the spectral modulation pattern containing the encoded CEP appears in the temporal domain, which allows for tracking with a relatively slow photodetector. To demonstrate the validity and performance of this concept, a CEP drift measurement was performed on the state-of-the-art mid-infrared (MIR) laser system at ELI-ALPS [5], which provides mid-IR laser pulses at 100 kHz. As a comparison, an alternative measurement was performed in parallel with a grating spectrometer (Fringeezz, Fastlite) [6] at 10 kHz sampling rate. The two recorded signals were synchronized and a decimated 10 kHz subset was extracted, where correlation between measurements is the highest. One of the main limitation of the DFT method originates from the time jitter between the output of the laser and the TTL signal used for triggering. This time jitter changes the time delay of the modulation pattern, creating an additional noise source for the measured relative CEP value. In order to perform truly time jitter-free single-shot CEP drift measurement, an additional CEP independent spectral modulation was introduced, which can be used to determine the noise originating from the jitter. The jitter-free decimated dataset against the grating spectrometer measurement is displayed on Fig. 1. The calculated CEP noises are summarized in Table 1. These values agree within the limit of the uncertainty of these measurements, validating that this new CEP drift measurement method is easily scalable to arbitrary repetition rates.
关键词： high repetition rate,mid-infrared laser system,Dispersive Fourier Transform,CEP drift measurement,single-shot
更新于2025-09-12 10:27:22
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Real-time dynamics of soliton collision in a bound-state soliton fiber laser
摘要： We experimentally investigated the soliton collisions between soliton molecules and deuterogenic solitons spontaneously generated on the continuous wave (cw) noise background in an ultrafast erbium-doped fiber laser mode locked with MoS2 saturable absorber (SA). The dynamics of the soliton collisions were observed using the time-stretch dispersion Fourier transform technique. The noise-induced deuterogenic solitons first undergo spectral broadening and wavelength shifting, then collide successively with a soliton molecule and eventually vanish. Within the simple collision framework, the spectral-temporal dynamics of soliton collision would help to unveil the self-stabilization mechanism of the soliton molecules in consideration of dispersive wave shedding. This nonlinear dynamics is similar to the soliton rain, except that complex condensed soliton phase is substituted with a soliton molecule.
关键词： time-stretch dispersive Fourier transform.,soliton molecule,molybdenum disulfide,soliton collision
更新于2025-09-12 10:27:22
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Real-time characterization of spectral instabilities in a mode-locked fibre laser exhibiting soliton-similariton dynamics
摘要： the study of dissipative solitons in mode-locked lasers reveals a rich landscape of interaction dynamics resulting from the interplay of nonlinearity, dispersion and dissipation. Here, we characterize a range of instabilities in a dissipative soliton fibre laser in a regime where both conventional soliton and similariton propagation play significant roles in the intracavity pulse shaping. Specifically, we use the Dispersive fourier transform technique to perform real-time spectral measurements of buildup dynamics from noise to the generation of stable single pulses, phase evolution dynamics of bound state “similariton molecules”, and several examples of intermittent instability and explosion dynamics. These results show that the instabilities previously seen in other classes of passively mode-locked fibre lasers are also observed in the presence of strong nonlinear attraction of similariton evolution in an optical fibre amplifier.
关键词： explosion dynamics,Dispersive fourier transform,similariton molecules,intermittent instability,dispersion,nonlinearity,mode-locked lasers,dissipative solitons,dissipation
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Optical Soliton Molecular Complexes in Ultrafast Fiber Lasers
摘要： Optical soliton molecules are under intense research focus, owing in particular to the interesting analogies between their self-assembly and internal dynamics, and those of matter molecules. Two interacting dissipative solitons can form a soliton-pair molecule, which can behave as a robust entity traveling around the cavity for an indefinite time [1]. The internal oscillatory dynamics of soliton molecules can be compared to molecular vibrations, though they are fundamentally different [2,3]. The recent experimental investigations in Refs. [2,3] have been enabled by the dispersive Fourier transform (DFT) technique, which allows recording spectral measurements at multi-MHz frame rates. They showed the existence of various oscillatory dynamics among soliton-pair and soliton-triplet basic molecules. Following the analogy between light and matter molecules, we now consider the experimental possibility of forming a “soliton molecular complex” (SMC), namely, a higher-order pattern obtained by the stable bonding of several soliton molecules, and investigating its complex internal dynamics. Such structure implies two different bond types, a strong one within each soliton molecule, and a weaker one to maintain the overall structure. We here report the first real-time recording and analysis of several internal dynamics of SMCs, which support this new structural concept. We shall describe our results concerning the dynamics of the fundamental SMC, made of two soliton-pair molecules, or (2+2)-SMC. The experimental configuration is based on an erbium-doped fiber ring laser, which is mode-locked by means of nonlinear polarization evolution (NPE), and its output spectrum analyzed in real-time through DFT [4]. The formation of various SMC is controlled by the laser output power and the tuning of NPE through the orientation of intracavity waveplates, in an experimental procedure which utilizes the hysteretic laser behavior in the multi-pulse regime. SMCs with sliding-phase and oscillating-phase dynamics have been characterized by real-time spectral interferometry measurements, thus revealing the dynamics of the major internal degrees of freedom of the complexes, namely the dynamics of the relative temporal and phase separations between the different soliton constituents. Numerical simulations confirm the experimental observations and offer an additional insight into the understanding of the complex dynamics of SMCs. By showing that soliton molecules can form various bonds according to the distance between soliton constituents, which we can manipulate, this work opens the way to the manipulation of large-scale optical- soliton complexes, which can be extended to other photonic platforms, such as microresonators.
关键词： soliton molecular complex,Optical soliton molecules,nonlinear polarization evolution,ultrafast fiber lasers,dispersive Fourier transform
更新于2025-09-11 14:15:04