Showing papers on "Fiber laser published in 2021"

Applications of Few-Layer Nb2C MXene: Narrow-Band Photodetectors and Femtosecond Mode-Locked Fiber Lasers.

Abstract: Although the physicochemical properties of niobium carbide (Nb2C) have been widely investigated, their exploration in the field of photoelectronics is still at the infancy stage with many potential applications that remain to be exploited. Hence, it is demonstrated here that few-layer Nb2C MXene can serve as an excellent building block for both photoelectrochemical-type photodetectors (PDs) and mode-lockers. We show that the photoresponse performance can be readily adjusted by external conditions and that Nb2C NSs exhibit a great potential for narrow-band PDs. The demonstrated mechanism was further confirmed by work functions predicted by density functional theory calculations. In addition, as an optical switch for passively mode-locked fiber lasers, ultrastable pulses can be demonstrated in the telecommunication and mid-infrared regions for Nb2C MXene, and as high as the 69th harmonic order with 411 MHz at the center wavelength of 1882 nm can be achieved. These intriguing results indicate that few-layer Nb2C nanosheets can be used as building blocks for various photoelectronic devices, further broadening the application prospects of two-dimensional MXenes.

Correction to: Abrupt initiation of material removal by focusing continuous-wave fiber laser on glass

Abstract: In the original publication of the article, Fig. 5 was incorrect. The correct Fig. 5 appears as below.

Fractional-order double-ring erbium-doped fiber laser chaotic system and its application on image encryption

Abstract: Laser chaotic systems have been extensively studied and applied in the past 20 years. However, the fractional form of the chaotic system of erbium-doped fiber laser has not been studied yet. Therefore, this paper proposes a fractional-order double-ring erbium-doped fiber laser chaotic system. The dynamic characteristics of the system are studied by phase diagram, bifurcation diagram, Lyapunov exponent spectrum, Spectral Entropy (SE) complexity, and coexisting attractors. At the same time, the digital circuit of the new system is implemented on the digital signal processing (DSP) platform. Compared with integer-order double-ring erbium-doped fiber laser chaotic systems, this fractional-order chaotic system has more complex dynamics and higher sensitivity and randomness. Finally, the fractional-order double-ring erbium-doped fiber laser chaotic system is applied to the image encryption algorithm with the improved gravitation model. In this encryption algorithm, the diffusion part uses an improved universal gravitation model, and the Zigzag algorithm scrambles the pixels. The security of the algorithm is analyzed. The analyses of the experimental results show that the image encryption scheme proposed in this paper has a good encryption effect and good security performance. The research in this paper provides theoretical guidance and experimental basis for the research of fractional-order laser chaotic secure communication.

Generation of polarization and phase singular beams in fibers and fiber lasers

Abstract: Cylindrical vector beams and vortex beams, two types of typical singular optical beams characterized by axially symmetric polarization and helical phase front, possess the unique focusing property and the ability of carrying orbital angular momentum. We discuss the formation mechanisms of such singular beams in few-mode fibers under the vortex basis and show recent advances in generating techniques that are mainly based on long-period fiber gratings, mode-selective couplers, offset-spliced fibers, and tapered fibers. The performances of cylindrical vector beams and vortex beams generated in fibers and fiber lasers are summarized and compared to give a comprehensive understanding of singular beams and to promote their practical applications.

Soliton Distillation of Pulses From a Fiber Laser

Abstract: An elegant method of nonlinear Fourier transform (NFT) has attracted worldwide research interests and such NFT methodology provides a new viewpoint on the physics of laser dynamics. Recently, the use of the NFT has been proposed for the investigation of laser radiation, indicating the capability to characterize the ultrashort pulse in the nonlinear frequency domain. Here, pure solitons are numerically separated from the resonant continuous wave (CW) background in a fiber laser by utilizing NFT. It is identified that the soliton and the resonant CW background have different eigenvalue distributions in the nonlinear frequency domain. Similar to water distillation, we propose the approach of soliton distillation, by making NFT on a steady pulse generated from a fiber laser, then filtering out the eigenvalues of the resonant CW background in the nonlinear frequency domain, and finally recovering the soliton by inverse NFT (INFT). Simulation results verify that the soliton can be distinguished from the resonant CW background in the nonlinear frequency domain and pure solitons can be obtained by INFT.

A six-octave optical frequency comb from a scalable few-cycle erbium fibre laser

Abstract: A coherent, compact and robust light source with coverage from the ultraviolet to the infrared is desirable for heterodyne super-resolution imaging1, broadband infrared microscopy2, protein structure determination3 and standoff trace-gas detection4. To address these demanding problems, frequency combs5 combine absolute frequency accuracy with sub-femtosecond timing and waveform control to enable high-resolution, high-speed and broadband spectroscopy6–9. Here we demonstrate a scalable source of near-single-cycle pulses from robust and low-noise erbium fibre (Er:fibre) technology. With a peak power of 0.56 MW we generate a comb spanning six octaves, from the ultraviolet (350 nm) to the mid-infrared (22,500 nm), achieving a resolving power of 1010 across 0.86 PHz of bandwidth. Second-order nonlinearities in LiNbO3, GaSe and CdSiP2 provide phase-stable infrared ultrashort pulses with simultaneous brightness exceeding a synchrotron10, while cascaded nonlinearities in LiNbO3 yield four octaves simultaneously (0.350–5.6 μm). We anticipate that these advances will be enabling for basic and applied spectroscopy, microscopy and phase-sensitive nonlinear optics. Ultralow-noise erbium:fibre comb technology allows the generation of a comb spanning six octaves, from the ultraviolet (350 nm) to the mid-infrared (22,500 nm), with a resolving power of 1010 across 0.86 PHz of bandwidth.

Reaching fiber-laser coherence in integrated photonics.

Abstract: We self-injection-lock a diode laser to a 1.41 m long, ultra-high Q integrated resonator. The hybrid integrated laser reaches a frequency noise floor of 0.006Hz2/Hz at 4 MHz offset, corresponding to a Lorentzian linewidth below 40 mHz-a record among semiconductor lasers. It also exhibits exceptional stability at low-offset frequencies, with frequency noise of 200Hz2/Hz at 100 Hz offset. Such performance, realized in a system comprised entirely of integrated photonic chips, marks a milestone in the development of integrated photonics; and, for the first time, to the best of our knowledge, exceeds the frequency noise performance of commercially available, high-performance fiber lasers.

Nonlinear Fourier transform enabled eigenvalue spectrum investigation for fiber laser radiation

Abstract: Fiber lasers are a paradigm of dissipative systems, which distinguish themselves from a Hamilton system where energy is conservative. Consequently, pulses generated in a fiber laser are always accompanied by the continuous wave (CW). Under certain hypothesis, pulses generated in a fiber laser can be considered as a soliton, a product of a Hamilton system. Therefore, all the descriptions of solitons of a fiber laser are approximate. Coexistence of solitons and the CW from a fiber laser prevents unveiling of real nonlinear dynamics in fiber lasers, such as soliton interactions. Pulse behavior in a fiber laser can be represented by the state of single pulse, the state of period doubling of single pulse, the states of two pulses either tightly bound or loosely distributed, the states of three pulses, and various combinations of the above-mentioned states. Recently, soliton distillation was proposed and numerically demonstrated based on the nonlinear Fourier transform (NFT) [J. Lightwave Technol.39, 2542 (2021)JLTEDG0733-872410.1109/JLT.2021.3051036]. Solitons can be separated from the coherent CW background. Therefore, it is feasible to isolate solitons from CW background in a fiber laser. Here, we applied the NFT to various pulses generated in a fiber laser, including single pulse, single pulse in period doubling, different double pulses, and multiple pulses. Furthermore, with the approach of soliton distillation, the corresponding pure solitons of those pulses are reconstructed. Simulation results suggest that the NFT can be used to identify soliton dynamics excluding CW influence in a fiber laser, which paves a new way for uncovering real soliton interaction in nonlinear systems.

3.5 kW coherently combined ultrafast fiber laser

Abstract: An ultrafast laser based on coherent beam combination of four ytterbium-doped step-index fiber amplifiers is presented The system delivers an average power of 35 kW and a pulse duration of 430 fs at 80 MHz repetition rate The beam quality is excellent (M2<124x110) and the relative intensity noise is as low as 1% in the frequency span from 1 Hz to 1 MHz The system is turn-key operable as it features an automated spatial and temporal alignment of the interferometric amplification channels

Ultra-long-period grating-based multi-wavelength ultrafast fiber laser [Invited]

Abstract: We propose and demonstrate the cascaded multi-wavelength mode-locked erbium-doped fiber laser (EDFL) based on ultra-long-period gratings (ULPGs) for the first time, to the best of our knowledge. Study found that the ULPG can be used as both a mode-locker for pulse shaping and a comb filter for multi-wavelength generation simultaneously. Using the dual-function of ULPG, three-, four-, five-, six-, and seven-wavelength mode-locked pulses are obtained in EDFL, seven of which are the largest number of wavelengths up to now. For the four-wavelength soliton pulses, their pulse width is about 7.8 ps. The maximum average output power and slope efficiency of these pulses are 8.4 mW and 2.03%, respectively. Besides the conventional pulses, hybrid soliton pulses composed of a four-wavelength pulse and single soliton are also observed. Finally, the effect of cavity dispersion on the multi-wavelength mode-locked pulses is also discussed. Our findings indicate that apart from common sensing and filtering, the ULPG may also possess attractive nonlinear pulse-shaping property for ultrafast photonics application.

1kW 1mJ 8-channel ultrafast fiber laser

Abstract: An ultrafast fiber chirped-pulse amplifier comprising 8 coherently combined amplifier channels is presented. The laser delivers 1 kW average power at 1 mJ pulse energy and 260 fs pulse duration. Excellent beam quality and low noise performance are confirmed. The laser has proven suitable for demanding scientific applications. Further power scaling is possible right away using even more amplifier channels

Ultrafast Photonics of Ternary Re x Nb (1- x) S 2 in Fiber Lasers

Abstract: Two-dimensional (2D) transition metal chalcogenides (TMCs) become more attractive upon addition of a third element owing to their unique structure and remarkable physical and chemical properties, which endow these materials with considerable potential for applications in nanoscale devices. In this work, a RexNb(1-x)S2-based saturable absorber (SA) device for ultrafast photonics applications is studied. The device is assembled by placing RexNb(1-x)S2 nanosheets with a thickness of 1-3 nm onto a microfiber to increase their compatibility with an all-fiber laser cavity. The prepared RexNb(1-x)S2-based device exhibits a modulation depth of 24.3%, a saturation intensity of 10.1 MW/cm2, and a nonsaturable loss of 28.5%. Furthermore, the RexNb(1-x)S2-based device is used to generate ultrashort pulses in an erbium-doped fiber (EDF) laser cavity. At a pump power of 260 mW, the EDF laser operates in a conventional soliton mode-locked region. The pulse width is 285 fs, and the repetition frequency is 61.993 MHz. In particular, the bound-state soliton mode-locking operation is successfully obtained in a pump power range of 300-900 mW. The bound-state pulses are formed by doubling identical solitons with a temporal interval of 0.8 ps. The output power is as high as 47.9 mW, and the repetition frequency is 123.61 MHz. These results indicate that the proposed RexNb(1-x)S2-based SAs have comparable properties to currently used 2D SAs and provide a basis for their application in the field of ultrafast photonics.

Direct generation of watt-level yellow Dy 3+ -doped fiber laser

Abstract: Yellow lasers (∼565–590 nm) are of tremendous interest in biomedicine, astronomy, spectroscopy, and display technology. So far, yellow lasers still have relied heavily on nonlinear frequency conversion of near-infrared lasers, precluding compact and low-cost yellow laser systems. Here, we address the challenge through demonstrating, for the first time, to the best of our knowledge, watt-level high-power yellow laser generation directly from a compact fiber laser. The yellow fiber laser simply consists of a Dy3+-doped ZBLAN fiber as gain medium, a fiber end-facet mirror with high reflectivity at yellow and a 450-nm diode laser as the pump source. We comprehensively investigated the dependence of the yellow laser performance on the output coupler reflectivity and the gain fiber length and demonstrated that the yellow fiber laser with an output coupler reflectivity of 4% and a gain fiber length of ∼1.8 m yields a maximum efficiency of 33.6%. A maximum output power of 1.12 W at 575 nm was achieved at a pump power of 4.20 W. This work demonstrated the power scaling of yellow Dy3+-doped ZBLAN fiber lasers, showing their promise for applications in ophthalmology, astronomical exploration, and high-resolution spectroscopy.

Stable transmission characteristics of double-hump solitons for the coupled Manakov equations in fiber lasers

Abstract: The fiber laser has become an ideal ultrashort pulse source because of its cheap structure, high integration, convenient and controllable output direction, which greatly promotes the development and application of ultrafast optics. This paper mainly focuses on the control and amplification of double-hump solitons in fiber lasers theoretically. The bilinear forms and soliton solutions of the coupled Manakov equations are presented, and the transmission of double-hump solitons is discussed. The factors affecting the stable transmission of double-hump solitons are analyzed. The relevant conclusions have important guiding significance for understanding the generation of stable double-hump solitons in fiber lasers.

Clinical Comparison of Super Pulse Thulium Fiber Laser and High-Power Holmium Laser for Ureteral Stone Management

Abstract: Purpose: To evaluate the efficacy of new super pulse thulium fiber laser (SP TFL) and compare it with holmium laser for ureterolithotripsy. Patients and Methods: A total of 174 patients with solita...

Three-Dimensional Vector Accelerometer Using a Multicore Fiber Inscribed With Three FBGs

Abstract: We have designed, fabricated, and characterized a fiber-optic three-dimensional vector accelerometer for vibration measurement The accelerometer is based on fiber Bragg gratings (FBGs) inscribed with three cores of seven-core fiber by femtosecond laser with a phase mask Through monitoring the wavelength shifts of two of the seven cores, we obtain the vibration azimuthal angle and the acceleration in the XY plane by angle reconstruction and algorithmic calculation Similarly, by monitoring the wavelength shift of the core fixed along the Z-axis, we obtain the vibration acceleration in the Z-axis direction The full 3D vector information about the vibration signal is obtained by vector synthesis The accelerometer has achieved a working frequency bandwidth from 10 to 220 Hz with the maximum sensitivity of 355 pm/g, and the best azimuthal angle accuracy of 0269 $^\circ$ in the linear range of 0 $^\circ$ –100 $^\circ$ and 170 $^\circ$ –280 $^\circ$ Moreover, it is possible to increase the overall bandwidth, sensitivity and accuracy of the azimuth of sensors in the XY plane by adjusting the length of the optical fiber and adjusting mechanical parameters to increase the bandwidth and sensitivity of the sensor in Z-axis Such improvements will further enhance application to small-scale seismic surveys

Synchronized multi-wavelength soliton fiber laser via intracavity group delay modulation.

Abstract: Locking of longitudinal modes in laser cavities is the common path to generate ultrashort pulses. In traditional multi-wavelength mode-locked lasers, the group velocities rely on lasing wavelengths due to the chromatic dispersion, yielding multiple trains of independently evolved pulses. Here, we show that mode-locked solitons at different wavelengths can be synchronized inside the cavity by engineering the intracavity group delay with a programmable pulse shaper. Frequency-resolved measurements fully retrieve the fine temporal structure of pulses, validating the direct generation of synchronized ultrafast lasers from two to five wavelengths with sub-pulse repetition-rate up to ~1.26 THz. Simulation results well reproduce and interpret the key experimental phenomena, and indicate that the saturable absorption effect automatically synchronize multi-wavelength solitons in despite of the small residual group delay difference. These results demonstrate an effective approach to create synchronized complex-structure solitons, and offer an effective platform to study the evolution dynamics of nonlinear wavepackets. The coherence degradation of pulses synchronized to optical cavities is an issue for ultrahigh-repetition-rate lasing. Here the authors demonstrate synchronized multi-wavelength mode-locked soliton fiber lasers generating ultrafast outputs from two to five wavelengths with a high sub-pulse repetition rate.

Core-clad terbium doped chalcogenide glass fiber with laser action at 5.38 μm

Abstract: The core-clad Tb3+-doped Ga-Ge-As-Se/Ge-As-S chalcogenide glass fiber is fabricated and tested in laser experiment. To prepare the high-purity terbium doped Ga-Ge-As-Se core glass, the special multi-stage purification technique is developed. The 1050 ppmw Tb3+-doped core Ga3.2Ge24.9As15.3Se56.6 glass is characterized by an extra-low content of limiting hydrogen impurity, high stability against crystallization and strong broadband photoluminescence in the middle infrared range. The doped chalcogenide fiber has a total diameter of 400 μm, a core diameter of 18 μm, and minimum optical losses of 3 ± 0.3 dB/m at a wavelength of 7.1 μm. Using a Tm3+ 1.98 μm fiber laser as a pump source, the threshold of 5.38 μm lasing with spike structure was reached in chalcogenide fiber for the first time.

Broadband Nonlinear Photonics in Few-Layer Borophene

Abstract: In this paper, 2D borophene is synthesized through a liquid-phase exfoliation. The morphology and structure of as-prepared borophene are systemically analyzed, and the Z-scan is used to measure the nonlinear optical properties. It is found that the saturable absorber (SA) properties of borophene make it serve as an excellent broadband optical switch, which is strongly used for mode-locking in near- and mid-infrared laser systems. Ultrastable pulses with durations as short as 792 and 693 fs are successfully delivered at the central wavelengths of 1063 and 1560 nm, respectively. Furthermore, stable pulses at a wavelength of 1878 nm are demonstrated from a thulium mode-locked fiber laser based on the same borophene SA. This research reveals a significant potential for borophene used in lasers helping extending the frontiers of photonic technologies.

How Lasers Ablate Stones: In Vitro Study of Laser Lithotripsy (Ho:YAG and Tm-Fiber Lasers) in Different Environments

Abstract: 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 ...

Ultra-Short Pulse Lasers for Microfabrication: A Review

Abstract: Ultra-short pulse lasers, generating coherent light pulses with pulse durations in the picosecond and femtosecond range, are becoming popular in precision laser microfabrication. They are benefiting not only from well-predicted laser ablation with the suppressed heat-affected zone but also by opening new processing opportunities, especially in transparent materials, due to enhanced non-linear interaction with the material. In this review, the evolution of various kinds of mode-locked lasers from a scientific toy to a robust industrial tool is reviewed. The utilization benefits of high-average-power, high-pulse-repetition-rate ultra-short pulse laser are closely related to beam shaping and manipulation techniques. Fast beam scanning with galvanometric and polygon scanners as well as multi-beam parallel processing methods were developed. Some hot applications areas are briefly described. The efficient use of photons from ultra-short pulse lasers pushed the development of optimization methods in the ablation process. Efforts toward upscaling the process by increasing the average power of mode-locked lasers made feedback to laser developers, and burst regime became a necessity as well as high-speed beam scanning devices. Unique opportunities of ultra-short pulses are successfully exploited in machining transparent materials, with glass separation being the leading application.

Harmonic mode-locking fiber ring laser with a pulse repetition rate up to 12 GHz

Abstract: We experimentally demonstrate a harmonically mode-locked Er-doped fiber laser The distinctive feature of the laser is highly stable pulse trains generated via self-starting hybrid mode-locking triggered by frequency-shifting and nonlinear polarization evolution A intra-cavity tunable bandpass filter allows getting a pulse repetition rate up to 12 GHz with local adjustment of the wavelength

Six-wavelength-switchable narrow-linewidth thulium-doped fiber laser with polarization-maintaining sampled fiber Bragg grating

Abstract: A compound-cavity-based six-wavelength-switchable single-longitudinal-mode (SLM) thulium-doped fiber laser (TDFL) with a homemade polarization-maintaining sampled fiber Bragg grating (PM-SFBG) is proposed and demonstrated. The PM-SFBG in the 2 μm band is studied theoretically and experimentally, and is utilized as a polarization-dependent multi-channel reflecting filter in a multi-wavelength-switchable fiber laser, both for the first time. The SLM lasing in each channel is guaranteed by using a tri-ring sub-cavity. 6 single-wavelength operations are easily obtained and switched each other, and the maximum power and wavelength fluctuations are as low as 0.71 dB and 0.02 nm, respectively. The frequency noise of each lasing wavelength is measured through an unbalanced Michelson interferometry system, and the linewidths for all six lasing wavelengths are among 0.60–1.08 kHz, calculated by the β-separation line method on the basis of the measured frequency noise spectra. Benefiting from the enhanced polarization hole burning effect formed in the gain fiber, 9 switchable dual-wavelength operations with different wavelength intervals and orthogonal polarizations at two lasing wavelengths are obtained with the maximum power and wavelength fluctuations of only 0.95 dB and 0.03 nm, respectively. We believe the proposed TDFL will find great applications as an ideal light source in free space optical communication and optical sensing.

Photonic device combined optical microfiber coupler with saturable-absorption materials and its application in mode-locked fiber laser.

Abstract: We demonstrated a mode-locked fiber laser based on a novel photonic device that combined optical microfiber coupler (OMC) and saturable absorption materials. The stable ultrafast laser was formed based on the interaction between the deposited Indium Antimonide (InSb) and the evanescent field on OMC. Different from optical microfiber (OM), OMC can directly output the mode-locked laser without additional beam splitting devices, which further improves the integrated characteristics of the fiber laser. The pulse duration of the output pulse is 405 fs at the central wavelength of 1560 nm. To the best of our knowledge, this is the first time that optical microfiber coupler based saturable absorber (OMC-SA) for mode-locked fiber laser is demonstrated.

>5kW Record High Power Narrow Linewidth Laser From Traditional Step-Index Monolithic Fiber Amplifier

Abstract: A high-power monolithic continuous wave (CW) Yb doped fiber amplifier at 1064 nm has been demonstrated based on traditional large mode area step-index fiber, which generated 5.07 kW narrow line-width laser with near diffraction-limited beam quality. At the maximal output power, >35dB OSNR has been achieved with line-width being 370pm, and the measured beam quality is M2x = 1.252, M2y = 1.322. The influence of cooling temperature on SRS has been investigated in high power fiber lasers, which shows that the SRS at 4kW has been suppressed 24 dB by lowering the temperature from 20°C to 8°C. To the best of our knowledge, this is the highest narrow line-width laser power generated from the traditional large mode area step-index monolithic fiber amplifier.

Laser Lithotripsy: The Importance of Peak Power and Pulse Modulation.

Abstract: Despite the worldwide spread of Ho:YAG lasers in urology departments, the physical principles behind their functioning may still seem obscure to many urologists Moreover, a new laser source, the thulium fiber laser (TFL), was recently approved for stone lithotripsy Here we describe the concepts of peak power and pulse modulation for laser lithotripsy, analyzing both Ho:YAG lasers and TFLs Different pulse modalities are available for Ho:YAG lasers—long and short pulses and Moses technology—each with a different pulse shape and peak power Lower peak power and a more rectangular pulse shape provide higher ablation efficiency and lower stone retropulsion These characteristics are perfectly embodied by TFL, which shows the most effective ablation efficiency in laboratory studies A long pulse is the most effective modality for Ho:YAG lasers Moses technology, despite its promising rationale, is not superior to long-pulse mode Clinical studies are needed in order to confirm these laboratory data Patient summary Laser lithotripsy is one of the main options for the treatment of urinary stones The peak power and pulse modulation influence the choice of the optimal laser mode for the treatment of urinary stones Thulium fiber lasers have shown the most favorable dusting profile in terms of both peak power and pulse modality in laboratory studies, but clinical evidence is still lacking

All-fiberized and narrow-linewidth 5 kW power-level fiber amplifier based on a bidirectional pumping configuration

Abstract: In this paper, an all-fiberized and narrow-linewidth 5 kW power-level fiber amplifier is presented. The laser is achieved based on the master oscillator power amplification configuration, in which the phase-modulated single-frequency laser is applied as the seed laser and a bidirectional pumping configuration is applied in the power amplifier. The stimulated Brillouin scattering, stimulated Raman scattering, and transverse mode instability effects are all effectively suppressed in the experiment. Consequently, the output power is scaled up to 4.92 kW with a slope efficiency of as high as approximately 80%. The 3-dB spectral width is about 0.59 nm, and the beam quality is measured to be M2∼1.22 at maximum output power. Furthermore, we have also conducted a detailed spectral analysis on the spectral width of the signal laser, which reveals that the spectral wing broadening phenomenon could lead to the obvious decrease of the spectral purity at certain output power. Overall, this work could provide a reference for obtaining and optimizing high-power narrow-linewidth fiber lasers.

Power stable 1.5-10.5 µm cascaded mid-infrared supercontinuum laser without thulium amplifier.

Abstract: We demonstrate a simple and power stable 15–105 µm cascaded mid-infrared 3 MHz supercontinuum fiber laser To increase simplicity and decrease cost, the design of the fiber cascade is optimized so that no thulium amplifier is needed Despite the simple design with no thulium amplifier, we demonstrate a high average output power of 866 mW Stability measurements for seven days with 8–9 h operation daily revealed fluctuations in the average power with a standard deviation of only 043% and a power spectral density stability of ±018dBm/nm for wavelengths <10µm The high-repetition-rate, robust, and cheap all-fiber design makes this source ideal for applications in spectroscopy and imaging