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Dissipative solitons (DSs), due to the complex interplay among dispersion, nonlinear, gain and loss, illustrate abundant nonlinear dynamics behaviors. Especially, dispersion plays an important role in the research of DS dynamics in ultrafast fiber lasers. Previous studies have mainly focused on the effect of even-order dispersion, i.e., group velocity dispersion (GVD) and fourth-order dispersion. In fact, odd-order dispersions, such as third-order dispersion (TOD), also significantly influences the dynamics of DSs. However, due to the lack of dispersion engineering tools, few experimental researches in this domain have been reported. In this work, by employing a pulse shaper in ultrafast fiber laser, an in-depth exploration of the DS dynamics influenced by TOD was conducted. With the increase of TOD value, the stable single DS undergoes a splitting into two solitons and then enters explosion state, and ultimately evolves into a chaotic state. The laser operation state is correlated to dispersion profile, which could be controlled by TOD. Here, the positive dispersion at long-wavelength side will be gradually shifted to negative dispersion by increasing the TOD, where soliton effect will drive the transitions. These findings offer valuable insights into the nonlinear dynamics of ultrafast lasers and may also foster applications involving higher-order dispersion.
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Multimode fiber lasers have become a new platform for investigating nonlinear phenomena since the report on spatiotemporal mode-locking. In this work, the multimode soliton pulsation with a tunable period is achieved in a spatiotemporal mode-locked fiber laser. It demonstrates that the pulsation period drops while increasing the pump power. Moreover, it is found that different transverse modes have the same pulsation period, asynchronous pulsation evolution and different dynamical characteristics through the spatial sampling technique and the dispersive Fourier transform technique. To further verify the experimental results, we numerically investigate the influences of the gain and the loss on the pulsation properties. It is found that within a certain parameter range, the pulsation period drops and rises linearly with the increase of the gain and the loss, respectively. The obtained results contribute to understanding the formation and regulating of soliton pulsations in fiber lasers.
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We develop an all polarization-maintaining (PM) 920â nm Nd-doped fiber amplifier delivering a train of pulses with â¼0.53â W average power and sub-50â fs duration. The sub-50â fs pulse benefits from the pre-chirping management method that allows for over 60â nm broadening spectrum without pulse breaking in the amplification stage. By virtue of the short pulse duration, the pulse peak power can reach to â¼0.31â MW in spite of the moderate average power. These results represent a key step in developing high-peak-power pulse Nd-doped fiber laser systems at 920â nm, which will find important applications in fields such as biomedical imaging, ultrafast optical spectroscopy, and excitation of quantum-dot single photon sources.
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Spatiotemporal mode-locked (STML) fiber lasers have become a new platform for investigating nonlinear phenomena. In this work, spatiotemporal dual-periodic soliton pulsation (SDSP) is firstly observed in an STML fiber laser. It is found that in the SDSP, the long-period pulsations (LPPs) of different transverse modes are synchronous, while the short-period pulsations (SPPs) exhibit asynchronous modulations. The numerical simulation confirms the experimental results and further reveals that the proportion of transverse mode components can manipulate the periods of the LPP and SPP but does not affect the synchronous and asynchronous pulsations of different transverse modes. The obtained results bring the study of spatiotemporal dissipative soliton pulsation into the multi-period modulation stage, which helps to understand the complex spatiotemporal dynamics in STML fiber lasers and discover new dynamics in high-dimensional nonlinear systems.
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Multimode fibers (MMFs) are emerging as promising transmission media for delivering images. However, strong mode coupling inherent in MMFs induces difficulties in directly projecting two-dimensional images through MMFs. By training two subnetworks named Actor-net and Model-net synergetically, [Nature Machine Intelligence2, 403 (2020)10.1038/s42256-020-0199-9] alleviated this issue and demonstrated projecting images through MMFs with high fidelity. In this work, we make a step further by improving the generalization ability to greyscale images. The modified projector network contains three subnetworks, namely forward-net, backward-net, and holography-net, accounting for forward propagation, backward propagation, and the phase-retrieval process. As a proof of concept, we experimentally trained the projector network using randomly generated phase maps and their corresponding resultant speckle images output from a 1-meter-long MMF. With the network being trained, we successfully demonstrated projecting binary images from MNIST and EMNIST and greyscale images from Fashion-MNIST, exhibiting averaged Pearson's correlation coefficients of 0.91, 0.92, and 0.87, respectively. Since all these projected images have never been seen by the projector network before, a strong generalization ability in projecting greyscale images is confirmed.
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Focusing light inside scattering media is a long-sought goal in optics. Time-reversed ultrasonically encoded (TRUE) focusing, which combines the advantages of biological transparency of the ultrasound and the high efficiency of digital optical phase conjugation (DOPC) based wavefront shaping, has been proposed to tackle this problem. By invoking repeated acousto-optic interactions, iterative TRUE (iTRUE) focusing can further break the resolution barrier imposed by the acoustic diffraction limit, showing great potential for deep-tissue biomedical applications. However, stringent requirements on system alignment prohibit the practical use of iTRUE focusing, especially for biomedical applications at the near-infrared spectral window. In this work, we fill this blank by developing an alignment protocol that is suitable for iTRUE focusing with a near-infrared light source. This protocol mainly contains three steps, including rough alignment with manual adjustment, fine-tuning with a high-precision motorized stage, and digital compensation through Zernike polynomials. Using this protocol, an optical focus with a peak-to-background ratio (PBR) of up to 70% of the theoretical value can be achieved. By using a 5-MHz ultrasonic transducer, we demonstrated the first iTRUE focusing using near-infrared light at 1053â nm, enabling the formation of an optical focus inside a scattering medium composed of stacked scattering films and a mirror. Quantitatively, the size of the focus decreased from roughly 1 mm to 160â µm within a few consecutive iterations and a PBR up to 70 was finally achieved. We anticipate that the capability of focusing near-infrared light inside scattering media, along with the reported alignment protocol, can be beneficial to a variety of applications in biomedical optics.
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Due to the fascinating features, pulsating solitons attract much attention in the field of nonlinear soliton dynamics and ultrafast lasers. So far, most of the investigations on pulsating soliton are conducted in Er-doped fiber lasers. In this work, we reported the periodic transition between two evolving pulsating soliton states in an Yb-doped fiber laser. By using the real-time measurement techniques, the spectral and temporal characteristics of this transition state were investigated. Two evolving soliton pulsation states have similar evolution process, i.e., from pulsating towards quasi-stable mode-locked states. However, the details of the two processes are different, such as the pulse energy levels, pulsating modulation depths, duration of quasi-stable mode-locked states. The transition between two evolving soliton pulsation states could be attributed to the interaction of the polarizer and the varying polarization states of the pulse inside the laser cavity. The experimental results will contribute to the further understanding of soliton pulsating dynamics in dissipative optical systems.
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We report, for the first time to the best of our knowledge, a spatiotemporal mode-locked (STML) multimode fiber laser based on nonlinear amplifying loop mirror (NALM), generating dissipative soliton resonance (DSR) pulses. Due to the complex filtering characteristics caused by the inherent multimode interference filtering structure and NALM in the cavity, the STML DSR pulse has wavelength tunable function. What's more, kinds of DSR pulses are also achieved, including multiple DSR pulses, and the period doubling bifurcations of single DSR pulse and multiple DSR pulses. These results contribute to further understand the nonlinear properties of STML lasers and may shed some light on improving the performance of the multimode fiber lasers.
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Multi-soliton operation in fiber lasers is a promising platform for the investigation of soliton interaction dynamics and high repetition-rate pulse. However, owing to the complex interaction process, precisely manipulating the temporal spacing of multiple solitons in a fiber laser is still challenging. Herein, we propose an automatic way to control the temporal spacing of multi-soliton operation in an ultrafast fiber laser by a hybrid genetic algorithm-particle swarm optimization (GA-PSO) algorithm. Relying on the intelligent adjustment of the electronic polarization controller (EPC), the on-demand temporal spacing of the double solitons can be effectively achieved. In particular, the harmonic mode locking with equal temporal spacing of double solitons is also obtained. Our approach provides a promising way to explore nonlinear soliton dynamics in optical systems and optimize the performance of ultrafast fiber lasers.
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The self-starting performance of a figure-9 fiber laser is critically dependent on the phase shift difference between the counter-propagating beams. Herein, we propose an effective approach to dynamically control the phase shift difference in a figure-9 fiber laser by utilizing the thermal nonlinearity of graphene-decorated microfiber device. With the adjustment of the control laser power injected into the graphene-decorated microfiber, the self-starting mode-locked threshold of the figure-9 fiber laser can be attained in a flexible pump power range, i.e., from 300â mW to 390â mW. These findings demonstrated that the graphene-decorated microfiber could act as a dynamical control device of phase shift difference for improving the performance of figure-9 fiber lasers, and might also open up new possibilities for applications of microfiber photonic devices in the field of ultrafast optics.
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The Mamyshev oscillator (MO) is a promising platform to generate high-peak-power pulse with environmentally stable operation. However, rare efforts have been dedicated to unveil the dynamics from seed signal to oscillator pulse, particularly for the multi-pulse operation. Herein, we investigate the buildup dynamics of the oscillator pulse from the seed signal in a fiber MO. It is revealed that the gain competition among the successively injected seed pulses leads to higher pump power that is required to ignite the MO, hence resulting in the higher optical gain that supports buildup of multiple oscillator pulses. The multiple oscillator pulses are identified to be evolved from the multiple seed pulses. Moreover, the dispersive Fourier transform (DFT) technique is used to reveals the real-time spectral dynamics during the starting process. As a proof-of-concept demonstration, a highly intensity-modulated pulse bunch was employed as the seed signal to reduce the gain competition effect and avoid the multi-pulse starting operation. The experimental results are verified by numerical simulations. These findings would give new insights into the pulse dynamics in MO, which will be meaningful to the communities interested in ultrafast laser technologies and nonlinear optics.
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Due to its unique geometric structure, the bidirectional ultrafast fiber laser is an excellent light source for dual-comb applications. However, sharing the same gain between the counter-propagating solitons also gives rise to complex dynamics. Herein, we report the anti-phase pulsation of counter-propagating dissipative solitons in a bidirectional fiber laser. The in-phase and anti-phase soliton pulsation can be manipulated by adjusting the intracavity birefringence. The periodic modulation of polarization-dependent gain (PDG) caused by polarization hole burning (PHB) in the gain fiber can be responsible for anti-phase pulsation of bidirectional dissipative solitons. These findings offer new, to the best of our knowledge, insights into the complex dynamics of solitons in dissipative optical systems and performance improvement of bidirectional ultrafast fiber lasers.
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OBJECTIVES: To evaluate the effectiveness of four large language models (LLMs) (Claude, Bard, ChatGPT4, and New Bing) that have large user bases and significant social attention, in the context of medical consultation and patient education in urolithiasis. MATERIALS AND METHODS: In this study, we developed a questionnaire consisting of 21 questions and 2 clinical scenarios related to urolithiasis. Subsequently, clinical consultations were simulated for each of the four models to assess their responses to the questions. Urolithiasis experts then evaluated the model responses in terms of accuracy, comprehensiveness, ease of understanding, human care, and clinical case analysis ability based on a predesigned 5-point Likert scale. Visualization and statistical analyses were then employed to compare the four models and evaluate their performance. RESULTS: All models yielded satisfying performance, except for Bard, who failed to provide a valid response to Question 13. Claude consistently scored the highest in all dimensions compared with the other three models. ChatGPT4 ranked second in accuracy, with a relatively stable output across multiple tests, but shortcomings were observed in empathy and human caring. Bard exhibited the lowest accuracy and overall performance. Claude and ChatGPT4 both had a high capacity to analyze clinical cases of urolithiasis. Overall, Claude emerged as the best performer in urolithiasis consultations and education. CONCLUSION: Claude demonstrated superior performance compared with the other three in urolithiasis consultation and education. This study highlights the remarkable potential of LLMs in medical health consultations and patient education, although professional review, further evaluation, and modifications are still required.
Asunto(s)
Educación del Paciente como Asunto , Urolitiasis , Humanos , Escolaridad , Lenguaje , Derivación y ConsultaRESUMEN
A highly stable figure-9 Yb-doped fiber laser with all polarization-maintaining (PM) double-cladding fiber is demonstrated. Through leveraging the saturable absorption effect of a nonlinear amplifying loop mirror, both the Q-switched and mode-locked operation are realized by adjusting the pump power. With increasing the pump power from the threshold to the maxima, the repetition rate of the Q-switched pulses is linearly increased from 14.9 kHz to 138.0 kHz with the pulse duration accordingly reduced from 3.9 µs to 970 ns. The corresponding maximum average power and pulse energy are respectively 2.34 W and 17 µJ, which are more than ten times larger than the common material-based Q-switched all-fiber lasers. In addition, in the process of increasing and decreasing the pump power, an optical bistability that manifested as a significant power jumping effect is observed, while its effect on the pulse repetition rate and duration is trivial. Whereas for the single pulse mode-locked operation, a maximum output power of 56.3 mW with a fundamental repetition rate of 12.5â MHz is realized, corresponding to a pulse energy of 4.5 nJ. To the best of our knowledge, it is much higher than the most of previous works concerning figure-9 all-PM-fiber lasers of which the emitted pulse energy is generally less than 1 nJ. After being compressed by a pair of diffraction grating, a minimum pulse width of 378 fs and a maximum peak power of 9.76â kW are respectively obtained. In addition, through characterizing the spectral and temporal properties of the laser source, the excellent stability of both the Q-switched and mode-locked operations is verified.
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The evolution of ultrafast laser technology hinges partially on the understanding of the soliton nonlinear dynamics. Recently, the concept of pure-quartic soliton (PQS) that arises from the balance of pure negative fourth-order dispersion (FOD) and nonlinearity was proposed to generate high peak power pulse. Herein, we investigate the generation of dissipative pure-quartic soliton (DPQS) in a fiber laser, which is balanced among the positive FOD, nonlinearity, gain and loss. The DPQS features the shape-preserving propagation despite the asymmetrical temporal profile at higher pulse energy. It is found that the asymmetrical temporal profile of DPQS is resulted from the mismatching of the phase shift profiles caused by self-phase modulation and FOD. Moreover, it is demonstrated that the DPQS possesses a higher energy-scaling ability compared to conventional dissipative soliton, owing to the nonlinear relationship between the pulse energy and pulse duration. These findings demonstrated that the employment of positive FOD could be a promising way for manipulation of optical pulse as well as the improvement of laser performance.
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Derived from oceanography, nowadays the investigation of rogue waves (RWs) has been widely spread in various fields, particularly in nonlinear optics. Passively mode-locked fiber laser has been regarded as one of the excellent platforms to investigate the dissipative RWs (DRWs). Here, we report the observation of DRW generation induced by single and multi-soliton explosions in a passively mode-locked fiber laser. It was demonstrated that through the gain-mediated soliton interactions, one soliton could erupt because of the explosion of another soliton in the laser cavity. Meanwhile, the high-amplitude waves, which fulfill the DRWs criteria, could be detected in the multi-soliton explosion states. The DRWs were identified by characterizing the peak intensity statistics of the time-stretched soliton profiles. Particularly, it was found that the ratio between the highest recorded amplitudes and significant wave heights (SWHs) of DRWs induced by multi-soliton explosions is higher than that by single-soliton explosion case. Our findings will further contribute to the understanding of the physical mechanisms of DRWs in the soliton explosion regime.
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The evolution of multiphoton microscopy is critically dependent on the development of ultrafast laser technologies. The ultrashort pulse laser source at 1.7 µm waveband is attractive for in-depth three-photon imaging owing to the reduced scattering and absorption effects in biological tissues. Herein, we report on a 1.7 µm passively mode-locked figure-9 Tm-doped fiber laser. The nonreciprocal phase shifter that consists of two quarter-wave plates and a Faraday rotator introduces phase bias between the counter-propagating beams in the nonlinear amplifying loop mirror. The cavity dispersion is compensated to be slightly positive, enabling the proposed 1.7 µm ultrafast fiber laser to deliver the dissipative soliton with a 3-dB bandwidth of 20 nm. Moreover, the mode-locked spectral bandwidth could be flexibly tuned with different phase biases by rotating the wave plates. The demonstration of figure-9 Tm-doped ultrafast fiber laser would pave the way to develop the robust 1.7 µm ultrashort pulse laser sources, which could find important application for three-photon deep-tissue imaging.
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We numerically investigate the pulsating dynamics of pure-quartic solitons (PQSs) in a passively mode-locked fiber laser. The bifurcation diagrams show that the PQS can alternate between the stable single soliton and pulsating regimes multiple times before transiting into the chaotic state. This multi-alternation behavior can be attributed to energy redistribution across the central part and the oscillating tails of the PQS, which is caused by an imperfect counterbalance between self-phase modulation (SPM)-induced and fourth-order dispersion (FOD)-induced phase shifts. Soliton creeping behavior can be observed during the pulsating process, accompanied by periodic asymmetric temporal profiles and central wavelength shifts of the PQS. These findings give new insights into the dynamics of PQSs in fiber lasers.
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We report a narrow bandwidth spatiotemporal mode-locked (STML) ytterbium-doped fiber laser, based on a homemade carbon nanotube/polyvinyl alcohol composite film and the multimode interference filtering effect. The wavelength-tunable narrow bandwidth STML operations combined with different pulse states are achieved, including single pulse, multiple pulses, and harmonics. The 3-dB bandwidth at the single-pulse state is 103 pm, while at the harmonic state, it is as narrow as 26 pm. To give an insight into the generation of the narrow bandwidth STML pulses, numerical simulations are performed. Such a laser has a wide range of potential applications in fields of optical communication and optical measurement, as well as provides a favorable platform for studying the evolution dynamics of multimode solitons.
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The optical memory effect is an interesting phenomenon exploited for deep-tissue optical imaging. Besides the widely studied memory effects in the spatial domain to accelerate point scanning speed, the spectral memory effect is also important in multispectral wavefront shaping. Although being theoretically analyzed for decades, quantitative studies of spectral memory effect on a variety of scattering media including biological tissue were rarely reported. In practice, quantifying the range of the spectral memory effect is essential in efficiently shaping broadband light, as it determines the optimum spectral resolution in realizing spatiotemporal focus through scattering media. In this work, we analyze the spectral memory effect based on a diffusion model. An explicit analytical expression involves the illumination wavelength, the diffusion constant, and the sample thickness is derived, which is consistent with the one in the literature. We experimentally quantified the range of spectral correlation for two types of biological tissue, tissue-mimicking phantoms with different concentrations, and diffusers. Specifically, for tissue-mimicking phantoms with calibrated scattering parameters, we show that a correction factor of more than 20 should be inserted, indicating that the range of spectral correlation is much larger than one would expect. This finding is particularly beneficial to multispectral wavefront shaping, as stringent requirements on the spectral resolution could be alleviated by at least one order of magnitude.