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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) - Raman Based Power Combining and Wavelength Conversion of Multiple Fiber Lasers — Number Scaling and Limits on Wavelength Separation
摘要： Cascaded Raman fiber lasers (CRFLs) based on random distributed feedback (RDFB) enable high-power fiber lasers at arbitrary wavelength bands [1,2]. To enable further power scaling in these systems, we recently proposed the use of multiple low-power pump sources instead of a single high-power pump laser [3]. Simultaneous power combining and wavelength conversion of two independent Ytterbium (Yb) lasers operating at different wavelengths into a single lasing wavelength at 1.5μm was demonstrated [3]. However, the questions on whether this technique works for more than 2 pump inputs and with arbitrary wavelength separation were unanswered. Here, we demonstrate that the technique works for more than 2 pump inputs and also with wavelength separation between the pump varying from 5nm to 29nm.
关键词： wavelength separation,power combining,Raman fiber lasers,Ytterbium lasers,wavelength conversion
更新于2025-09-12 10:27:22
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Experimental exploration of mode-locking evolution mechanism in dual-ring fiber laser
摘要： We explored experimentally the mode-locking (ML) evolution mechanism of a dual-ring fiber laser. Increase of the total pump power up to 860 mW allowed the observation of the state changes from single-ring ML, dual-ring ML, to dual-ring self-starting ML. Moreover, a group of wave plates and a fixed polarization beam splitter were applied in each subring as precise attenuators. Rotation of each wave plate for an entire turn allowed the investigation of the ML evolution of the two subrings based on the intracavity power variation in each subring. The variation periodicity of the output power was analyzed for each subring and was found to be consistent with the theoretical results. Furthermore, the ML detachment threshold in each subring was estimated to explain the ML evolution. Our study provides a deeper understanding of the ML evolution in dual-ring fiber lasers and can aid their future optimal design for dual comb applications.
关键词： Fiber lasers,Mode-locking evolution,Cascaded nonlinear processes,Mode-locked lasers,Ultrafast mechanism
更新于2025-09-12 10:27:22
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Widely Tunable, 25-mW Power, Ti:sapphire Crystal-Fiber Laser
摘要： Using a glass-clad Ti:sapphire crystal fiber (CF) as the gain medium, we demonstrate for the first time a diode-pumped, 25-mW tunable laser with a 180-nm tuning range. Active medium is a 2.4-cm long, a-cut Ti:sapphire CF we have drawn with an elliptical core of 13-μm diameter in the [0001] axis and 15.5-μm diameter in the [1ˉ100] axis. The CF is cladded with silica and has high efficiency (88%) of coupling to the pump, a diode laser emitting 1-W at 520-nm. A blazed grating provides a continuous smooth tuning on the wavelength range from 700 to 880 nm.
关键词： fiber lasers,Tunable solid-state lasers,crystalline materials,optical coherence tomography
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) - Generating Picosecond Pulses from Mid-Infrared Fiber Lasers using Frequency-Shifted Feedback
摘要： Ultrafast mode-locked ?ber lasers in the near infrared have enabled a host of key applications in a variety of ?elds such as medicine and defense. In recent years there has been signi?cant interest in pushing the emission wavelength of these ?ber laser systems to the mid infrared (MIR 3 - 5 μm) due to the presence of strong molecular absorption features in this spectral range. Various techniques to achieve this have been demonstrated, with a majority of the work focused on implementation of loss modulation via real saturable absorbers. While this has been successful in generating picosecond pulses in the mid-infrared [1], commercial availability of absorbers is currently limited, and alternatives such as nanomaterials (graphene, black phosphorous) raise questions regarding long-term stability. Virtual absorbers based on nonlinear polarization evolution have shown comparatively superior performance in terms of pulse duration [2] but this method is highly sensitive to small environmental perturbations. In this work we will present recent efforts to offer an alternative method of ‘mode-locking’ using frequency-shifted feedback (FSF) [3,4]. The method requires a frequency shifting element in the cavity, which in this case is an acousto-optic ?lter or modulator. Initial efforts are based on a dysprosium-doped ZBLAN ?ber laser pumped with an Er:ZBLAN ?ber laser (Fig. 1a). An acousto-optic tunable ?lter (AOTF) provides the requisite frequency shift and also a means of tuning the emission wavelength. The broad gain bandwith of dysprosium allows this system to be tuned over a range of 330 nm (Fig. 1b) with a pulse duration that remains consistent at 33 ps. Pulse formation dynamics are investigated numerically and will be presented with consideration to the various parameters that impact realized pulse duration. Of these it will be shown that a ?ltering effect is necessary in addition to the frequency shifting, with the AOTF providing this in the dysprosium case. Filter bandwidth is shown to in part dictate pulse duration, with a wider ?lter supporting shorter pulses. To investigate this we replace the dysprosium cavity with a similar holmium-doped system which replaces the AOTF with a simple acousto-optic modulator (AOM). The broader acceptance bandwidth of the AOM results in improved performance and a pulse duration of less than 5 ps (Fig.1 c-e), which surpasses the current record performance of mid-IR saturable absorber ?ber lasers systems.
关键词： holmium-doped system,frequency-shifted feedback,dysprosium-doped ZBLAN fiber laser,picosecond pulses,acousto-optic tunable filter,mid-infrared fiber lasers
更新于2025-09-12 10:27:22
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Self-starting all-fiber mode-locked laser based on Mamyshev mechanism with high-energy pulse generation at 1550 nm
摘要： An all-fiber mode-locked laser based on Mamyshev mechanism operating at 1550 nm was demonstrated. Self-phase modulation and offset spectral filtering provide high peak-power pulse selection in the laser cavity and induce mode locking. With selected operating parameters, the all-fiber mode-locked laser easily achieves mode locking without external seed pulses or auxiliary starting arms, making the laser convenient to operate. Pulses with maximum energy ~18 nJ and width 230 fs are obtained. Pulse width is almost unchanged with increasing pump power, while pulse energy increases linearly. Starting of the mode-locked laser based on Mamyshev mechanism and output spectra with different pump powers were experimentally investigated.
关键词： Fiber nonlinear optics,Fiber lasers,Laser mode locking,Laser cavity resonators
更新于2025-09-12 10:27:22
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Directly blue diode-pumped green self-Q-switched $\text{Ho}^{3+}$-doped fluoride all-fiber laser at ~550nm
摘要： We successfully demonstrate a blue diode-pumped green single-wavelength self-Q-switched Ho3+:ZrF4-BaF2-LaF3-AlF3-NaF (Ho:ZBLAN) all-fiber laser emitting at ~550 nm. Such a green laser, being a very simple device, consists of a 15-cm-long Ho:ZBLAN fiber and a pair of fiber input/output mirrors. The Ho:ZBLAN fiber not only acts as a gain medium but also works as a saturable absorber (SA). The modulation mechanism is induced by the ground-state reabsorption effect in an ineffectively pumped section of the active fiber. Stable Q-switching pulses are characterized by a 889 ns of minimum pulse duration and a 264 nJ of maximum energy pulse at a repetition rate of 67.25 kHz. We believe that this work could provide an appreciable alternative for next generation of pulsed green laser source, which finds the applications in the medical diagnosis, optical imaging, and industrial manufacturing.
关键词： Ho-doped fiber,blue-diode pumping,Optical Fiber lasers,Q-switching,visible laser
更新于2025-09-12 10:27:22
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Dual-wavelength dissipative solitons in an anomalous-dispersion-cavity fiber laser
摘要： We report on the experimental observation of dual-wavelength dissipative soliton operation of a fiber laser with net anomalous cavity dispersion. Different from the dual- or multi-wavelength soliton operation of fiber lasers where mode locking is used to initiate soliton formation, no mode locking occurs in our fiber laser. Instead, soliton formation is through the dissipative mechanism caused by the effective gain bandwidth limitation. Either dual-wavelength scalar, or vector, or induced dissipative solitons are experimentally obtained. Their robustness is experimentally confirmed.
关键词： fiber lasers,pulse propagation and temporal solitons,nonlinear fiber optics
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) - All-Fiber Single-Mode PM Yb-Doped Pre-Amplifier at 0.976 μm
摘要： Yb-doped fiber lasers operating near 0.98 μm attract considerable interest in recent years. In particular, the pulsed lasers at 0.98 μm are promising for frequency doubling and quadrupling. At the same time, the Yb-doped fibers optimized for 0.98 μm generation have been designed to achieve high laser efficiency at a high average output power and hardly can be used in preamplifier stages or in scheme of master oscillator lasers. Such fibers have a large core diameter (in excess of 25 μm) and high splicing losses with standard single-mode step-index fibers (maximum diameter of those does not exceed 10 μm). The pulsed lasers based on such fibers require utilization of bulk elements [1, 2] that eliminate advantageous of all-fibers schemes (compactness, reliability, low-cost). Moreover, due to a very high lasing threshold (tens of Watts) such fibers are unsuitable for signal amplification to a middle-level output power (0.1-1 W), required for pre-amplifiers and for many of master-oscillator schemes. In opposite, core-pumped schemes are power-limited by available single-mode pump diodes at 915 nm and typically do not allow output power higher than ~100 mW. In the present work, to create efficient pre-amplifier for 0.98 μm spectral range we designed and fabricated a special polarization-maintaining (PM) Yb-doped fiber with reduced mode field diameter (MFD) to make it compatible with standard single-mode fibers. The developed fiber was based on a ring-doping design (cladding was partially doped with Yb-ions), which allowed us to fabricate a relatively small core and, simultaneously, keep a reasonably high lasing efficiency. The lasing threshold was reduced by choosing of the silica cladding size as small as 80 μm. The fiber core was fabricated based on a photodarkening free P2O5-Al2O3-SiO2 glass matrix. The fiber end image is shown in Fig.1a. The MFD of the fundamental mode along the x and y axes were 12 μm and 15 μm, respectively, which ensured reasonably low splicing losses of the fabricated fiber and standard single-mode optical fibers. The cladding absorption near 915 nm was 3.4 dB/m, optimal fiber length was about 45 cm. To create an all-fiber amplifier scheme, we developed a special pump and signal combiner (2+1-to-1 configuration) based on a PM step-index fiber with core and cladding diameters of 10 μm and 80 μm, respectively. The slope pump to signal conversion efficiency was 11.5% in the scheme with co-propagated signal (100 mW) and pump (Fig. 1b). A low lasing threshold (about 4 W) allowed us to achieve output power of few hundred mW using pump power of less than 10 W, which outperforms more “efficient” amplifier designs where to achieve positive gain the pump power as high as 10-20 W is required [3, 4]. Furthermore, the fiber was found to be promising for a small signal amplification (Fig. 1c). Ratio of amplified signal power to power of amplified spontaneous emission (ASE) near 0.98 μm was about 20 dB even for input signal as small as 1 mW.
关键词： polarization-maintaining,Yb-doped fiber lasers,pre-amplifier,single-mode fibers,ring-doping design
更新于2025-09-12 10:27:22
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Breathing dissipative solitons in mode-locked fiber lasers
摘要： Dissipative solitons are self-localized coherent structures arising from the balance between energy supply and dissipation. Besides stationary dissipative solitons, there are dynamical ones exhibiting oscillatory behavior, known as breathing dissipative solitons. Substantial interest in breathing dissipative solitons is driven by both their fundamental importance in nonlinear science and their practical applications, such as in spectroscopy. Yet, the observation of breathers has been mainly restricted to microresonator platforms. Here, we generate breathers in a mode-locked fiber laser. They exist in the laser cavity under the pump threshold of stationary mode locking. Using fast detection, we are able to observe the temporal and spectral evolutions of the breathers in real time. Breathing soliton molecules are also observed. Breathers introduce a new regime of mode locking into ultrafast lasers. Our findings may contribute to the design of advanced laser sources and open up new possibilities of generating breathers in various dissipative systems.
关键词： spectroscopy,breathing solitons,mode-locked fiber lasers,dissipative solitons,nonlinear science
更新于2025-09-12 10:27:22
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Supercontinuum Generation from a Thulium Ultrafast Fiber Laser in a High NA Silica Fiber
摘要： A broadband supercontinuum is generated from a thulium ultrafast soliton fiber laser in a high numerical aperture silica fiber with low nJ seed pulse energies. Amplification of a thulium based ultrafast soliton ring fiber laser in two customized thulium doped fiber amplifiers provides pulses varying in energy between 1.8 nJ and 13.5 nJ. Coupling these seed pulses into a high numerical aperture silica fiber UHNA 7 of varying length, a systematic study of the impact of pulse energy, pulse duration and nonlinear fiber length is conducted. Based on the normal dispersion, self-phase modulation dominates for lower pump power values and results in a symmetric spectral broadening process. For higher pulse energies, four-wave mixing and Raman scattering contribute to a strong red-shift of the spectrum beyond 2.3 μm. For a fiber length of 20 m of UNHA 7, a broadband supercontinuum spanning from 1.7 μm to 2.33 μm is generated with a 20 dB spectral bandwidth of 502 nm with an output pulse energy of 4.4 nJ, corresponding to an output power of 92 mW. This represents a low seed energy threshold for efficient flat supercontinuum generation at infrared wavelengths.
关键词： Supercontinuum generation,Ultrafast optics,Fiber lasers,Thulium
更新于2025-09-12 10:27:22