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Switchable multiwavelength thulium-doped fiber laser with cylindrical vector beam emission
摘要： We experimentally demonstrate a switchable multiwavelength thulium-doped fiber laser with cylindrical vector beam (CVB) emission, which is the first report, to our best knowledge, on the generation of CVBs in a 2 μm wavelength band. The Sagnac loop filter, made up of a 50:50 coupler, a section of polarization-maintaining fiber and a polarization controller, serves as a periodical filter and accounts for the excitation of multiwavelength channels. The mode-selective coupler consisting of both tapered single-mode and four-mode fibers has been designed and fabricated as a mode converter from LP01 to LP11 mode with a purity of >80%. By adjusting the polarization controllers, laser outputs with 1–3 switchable wavelengths have been realized in the spectrum ranging from 1988–1998 nm. The laser could find miscellaneous applications in wavelength/mode-division multiplexing system, etc.
关键词： cylindrical vector beams (CVBs),thulium-doped fiber laser (TDFL),multiwavelength fiber laser,mode conversion
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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Rare Earth Doped Optical Fibers with Multi-section Core
摘要： The gain bandwidth of a single-mode fiber is limited by the atomic transitions of one rare earth gain element. Here we overcome this long-standing challenge by designing a new single-mode fiber with multi-section core, where each section is doped with different gain element. We theoretically propose and experimentally demonstrate that this configuration provides a gain bandwidth well beyond the capability of conventional design, whereas the inclusion of multiple sections does not compromise single-mode operation or the quality of the transverse modal profile. This new fiber will be beneficial in realizing all fiber laser systems with few-cycle pulse duration or octave tunability.
关键词： Rare Earth Doped Optical Fibers,Gain Bandwidth,Fiber Laser Systems,Single-mode Fiber,Multi-section Core
更新于2025-09-12 10:27:22
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Titanium dioxide-based picoseconds pulsed fiber laser performances comparison in the 1.5-micron region
摘要： We demonstrated and compared picoseconds pulsed fiber lasers based on Titanium dioxide based saturable absorbers (SAs); 20 cm long Titanium dioxide-doped fiber (TiO2DF) and Titanium dioxide PVA film (TiO2PF) in the 1.5-micron region. The laser cavity utilized 2.4 m long Erbium-doped fiber (EDF) as the gain medium. A self-starting pulsed laser with a consistent repetition rate of ~1 MHz emerged stably with the incorporation of TiO2 based SAs. The TiO2DF SA produced 9.74 ps pulsed laser at a central wavelength of 1553 nm within a pump power range of 106-142 mW. The fiber SA promoted slightly higher slope efficiency and maximum pulse energy of 13.17% and 8.56 nJ, respectively in comparison with the film SA. On the other hand, the TiO2PF SA generated stable 3.89 ps pulsed laser at an operating wavelength of 1560 nm within 86-142 mW pump power range. The film SA also produced slightly greater maximum output power of 12.17 mW and maximum peak power of 3.43 kW, respectively at the maximum pump power. The results confirmed that both TiO2 SAs can be good alternative pulse modulator in the 1.5-micron region.
关键词： Titanium dioxide,fiber saturable absorber,Optical fiber laser,thin film
更新于2025-09-12 10:27:22
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The Theoretical Calculation and Influencing Factors of Yb<sup>3+ </sup>Doped Double-Clad Fiber Laser
摘要： The energy level structure of Yb3+ is analyzed, and a theoretical model is established. The influence of pumping power, fiber length, reflectance of cavity mirror and other related parameters on the performance of the laser is analyzed. The maximum output power can be achieved at a certain reflectance. The higher the input pump power, the smaller the reflectance of the rear mirror which obtains the maximum output power. For different pumping wavelengths, the optimal length of the gain fiber is not the same, and it is also different from the optimal length determined by the minimum pumping threshold. Therefore, in the design of fiber lasers, we should consider comprehensively to determine the appropriate fiber length. Reducing inner raduis is beneficial to improving slope efficiency when the characteristics of the fiber itself remain unchanged.
关键词： Energy Level Structure,Yb3+doped,Fiber Laser,Double-clad Fiber
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) - Tunable All-Fiber Laser for Remote Sensing of Methane Near 3.4 μm
摘要： The mid-infrared (MIR) region of the optical spectrum has drawn considerable scientific interest in the past few years. Indeed, several molecules relevant to medical or environmental conundrums exhibit strong absorption lines in this region: for instance, methane lines in the MIR are up to 100 times stronger than in the near-infrared [1]. In turn, fiber lasers have long stood as prime candidates for remote gas detection in outdoor environments, given their exemplary robustness, power scaling and beam quality. However, while several previous contributions have targeted methane bands under 3.3 μm in wavelength [2], little work has been done to push fiber laser detection tools past 3.4 μm, where methane absorption lines are mostly decoupled from the absorption spectra of water and other atmospheric constituents. This is especially relevant when probing CH4 through a gas mixture with relatively high water content, such as when studying gas emission from methane-rich thermokarst lakes in northern regions. To this end, we present a tunable all-fiber laser emitting near 3.43 μm and operating at high average power. The laser design (Fig. 1) is based on an all-fiber dual-pumping scheme [3], which combines core-pumping at 1976 nm with clad-pumping at 976 nm in a single-mode erbium-doped fluoride glass fiber to reach, in the present case, up to 3 W of output power at the desired wavelength. The laser cavity itself is delimited by two fiber Bragg gratings (FBG): a highly-reflective (HR) FBG at the input, which has a narrow bandwidth to dictate the laser wavelength, and a lowly-reflective (LR) FBG at the output, which has a large bandwidth to accommodate shifts of the HR FBG. Tuning of the laser cavity is achieved by mechanically stretching (i.e. lengthening) the HR FBG via the beam bending technique [4]. The HR FBG is nested within an Invar-based metallic groove and fixed using a polymer of sufficient elasticity, the groove is then deformed using a piezoelectric actuator (PA), allowing for rapid and precise wavelength tuning over a wavelength range of a few nanometers. Figure 2 compares normalized spectra of the laser emission at various commanding voltages for the PA along with the absorption spectrum of methane as given by the HITRAN database [1]. As can be seen on Fig.2, the presence of consecutive extrema (min-max) allows for quick referencing of the measurement during each tuning cycle. Early gas cell experiments and further engineering refinement show good promise for future deployment in northern regions by climate scientists.
关键词： methane,remote sensing,mid-infrared,piezoelectric actuator,fiber Bragg gratings,tunable all-fiber laser
更新于2025-09-12 10:27:22
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Q-switching Zirconia-Erbium-doped Pulsed Fiber Laser with MWCNTs-PEO as Saturable Absorber
摘要： Q-switched pulses provide a significant contribution to recent biomedical applications such as laser treatment, medical imaging, biomedical diagnoses and spectroscopy due to high efficiency, compact device, less footprint, flexibility and cost effective. A successful generation of Q-switching pulsed fiber laser by using a homemade fiber of zirconia-based erbium-doped fiber (Zr-EDF) with the utilization multi-walled carbon nanotubes-polyethylene oxide (MWCNTs-PEO) as saturable absorber is reported. The active medium is 1 meter length of Zr-EDF with -0.6 ps2 group delay dispersion (GDD) for overall setup arrangement. At maximum pump power 126 mW, the repetition rate, pulse duration, output power and pulse energy are 17.3 kHz, 7.57 μs, 1.13 mW and 65.03 nJ, respectively.
关键词： MWCNTs-PEO,Saturable Absorber,Pulsed Fiber Laser,Q-switching,Zirconia-Erbium-doped fiber
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) - Development of Figure-8 Variable Pulse Width Fiber Laser using Coherent Resonator Coupling Technology
摘要： A femtosecond pulsed laser has an extremely short pulse width and high peak power and is used for the field of microfabrication. On the other hand, laser cutting and drilling requires picosecond pulsed laser with high pulse energy. In general, a diffraction grating or a band pass filter is used to control pulse width. However, these components are not affordable and the optical system with them becomes complicated. Therefore, we have developed all fiber variable pulse width laser by applying a coherent resonator coupling technology that increases the output power by coupling the phases of longitudinal modes generated by sharing an output coupler in multiple laser resonators. In the coherent resonator coupling, resonator length difference decreases coupled longitudinal modes and narrows spectral width (?ν). Thus, pulse width (?t) is widened according to equation (1). ?t ? ?ν = const (1) We will describe the configuration of the resonator used in the experiment. A resonator coupling technology is applied to a figure-8 fiber laser. The figure-8 fiber laser is a ring resonator that contains a nonlinear optical loop mirror. It operates as a resonator only when a phase difference occurs between the clockwise light that travels through the loop of the mirror and the counter-clockwise one. The phenomenon functions as a saturable absorption effect and generates femtosecond pulses. Further, we use a variable delay line in one of the resonator to control resonator length difference. Figure 1 shows the configuration of the figure-8 variable pulse width fiber laser and Fig. 2 shows the configuration of a nonlinear optical loop mirror.
关键词： femtosecond pulsed laser,figure-8 fiber laser,picosecond pulsed laser,nonlinear optical loop mirror,coherent resonator coupling technology
更新于2025-09-12 10:27:22
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How Lasers Ablate Stones: In-vitro Study of Laser Lithotripsy (Ho:YAG and Tm-fiber lasers) in Different Environments
摘要： Introduction. There are two main mechanisms of stone ablation with long‐pulsed infrared lasers: photothermal and photomechanical. Which of them is primary in stone destruction is still a matter of discussion. Water holds importance in both mechanisms but plays a major role in the latter. We sought to identify the prevailing mechanism of stone ablation by evaluating the stone mass‐loss after lithotripsy in different media. Material and methods. We tested a Ho:YAG laser (100W, Lumenis, USA), a Tm‐fiber laser U1 (TFL U1), (120W, NTO IRE‐Polus, Russia) and a Superpulse Tm‐fiber laser U2 (TFL U2) (500W, NTO IRE‐Polus, Russia). A single set of laser parameters (15 W = 0.5 J × 30 Hz) was used. Contact lithotripsy was performed in phantoms (BegoStones) in different settings: a) hydrated phantoms in water; b) hydrated phantoms in air; с) dehydrated phantoms in water; d) dehydrated phantoms in air. Laser ablation was performed with total energy of 0.3 kJ. Phantom mass‐loss was defined as the difference between the initial phantom mass and the final phantom mass of the ablated phantoms. Results. All lasers demonstrated effective ablation in hydrated phantoms ablated in water, no visual differences between the lasers were detected. The ablation of dehydrated phantoms in air was also effective with visible vapor during ablation and condensation on the cuvette wall. Dehydrated phantoms in water and in air shown minimal to no ablation accompanied with formation of white crust on phantoms surface. Among laser types, TFL U2 had the highest phantom mass‐loss in all groups except for dehydrated phantoms ablated in air. Conclusions. Our results suggest that both photothermal and thermomechanical ablation mechanisms (explosive vaporization) occur in parallel during laser lithotripsy. In Ho:YAG and TFL U2 stone ablation, explosive vaporization prevail, while in TFL U1 ablation, photothermal mechanism appear to predominate.
关键词： laser lithotripsy,Ho:YAG laser,Thulium fiber laser,stone disease
更新于2025-09-12 10:27:22
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Low-cost Custom Fabrication and Mode-locked Operation of an All-normal-dispersion Femtosecond Fiber Laser for Multiphoton Microscopy
摘要： A protocol is presented to build a custom low-cost yet high-performance femtosecond (fs) fiber laser. This all-normal-dispersion (ANDi) ytterbium-doped fiber laser is built completely using commercially available parts, including $8,000 in fiber optic and pump laser components, plus $4,800 in standard optical components and extra-cavity accessories. Researchers new to fiber optic device fabrication may also consider investing in basic fiber splicing and laser pulse characterization equipment (~$63,000). Important for optimal laser operation, methods to verify true versus apparent (partial or noise-like) mode-locked performance are presented. This system achieves 70 fs pulse duration with a center wavelength of approximately 1,070 nm and a pulse repetition rate of 31 MHz. This fiber laser exhibits the peak performance that may be obtained for an easily assembled fiber laser system, which makes this design ideal for research laboratories aiming to develop compact and portable fs laser technologies that enable new implementations of clinical multiphoton microscopy and fs surgery.
关键词： fiber laser,multiphoton microscopy,low-cost,mode-locking,Issue 153,femtosecond pulsed laser,Engineering,custom fabrication
更新于2025-09-12 10:27:22