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Quasi-all-fiber structure CW mid-infrared laser emission from gas-filled hollow-core silica fibers
摘要： A quasi-all-?ber structure CW mid-infrared ?ber lasers based on gas-?lled hollow-core ?bers (HCFs) is ?rstly reported here. Through a thermally tapered single-mode ?ber, the CW tunable 1.5 μm ?ber pump light is coupled into an acetylene-?lled anti-resonance HCFs, and the coupling point is sealed with epoxy glue to ensure the stability and gas tightness, then the HCFs is ?lled with acetylene gas by a specially designed small gas cell, just like an end cap. When the pump is precisely tuned to the resonance with the absorption lines of acetylene, CW mid-infrared emission around 3.1–3.2 μm is generated at room temperature with maximum power of ~180 mW and slope e?ciency of ~14%. The laser threshold is also discussed as function of acetylene pressure. This work opens new opportunities for all-?ber mid-infrared lasers of new wavelengths those unavailable for traditional rare-earth-doped ?bers.
关键词： Molecular gas lasers,Infrared and far-infrared lasers,Fiber lasers,Photonic crystal ?bers
更新于2025-09-11 14:15:04
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Femtosecond Soliton Erbium-doped Fiber Laser with a Symmetrical GIMF-SIMF-GIMF Saturable Absorber
摘要： A femtosecond soliton erbium-doped fiber ring laser with the symmetrical saturable absorber (SA) of graded index multimode fiber-step index multimode fiber-graded index multimode fiber (GIMF-SIMF-GIMF) is proposed and proved. Based on the nonlinear multimode interference (NL-MMI) effect of SA, the fiber laser achieved femtosecond soliton mode-locking operation and repetition rate tuning. The duration of soliton was 364 fs at 1562.5 nm and repetition rate was tunable from 10.29 MHz to 763.36 MHz. In the structure of SA, a short step index multimode fiber (SIMF) was inserted between two graded index multimode fibers (GIMFs) to generate more high-order modes，adjust the self-focusing length, and improve operation stability of mode-locked fiber laser. The SA also has the advantages of immunity to the external environment variation, high damage threshold and inoxidizability, which make the laser operate stably for a long time.
关键词： Femtosecond soliton,ultrafast fiber lasers.,mode-locked fiber lasers,nonlinear multimode interference
更新于2025-09-11 14:15:04
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Unified Formalism for Erbium-Doped Fiber Amplifiers and Lasers
摘要： A comprehensive and integrated exact analytical formalism is presented for erbium-doped fiber amplifiers and lasers (EDFALs) in one single configuration based on solutions of a system of rate and propagation equations represented by a homogenously broadened four band transition scheme while incorporating amplified spontaneous emission and excited state absorption effects. The formalism, under steady-state conditions, concurrently provides considerable insight into physical characteristics underlying phenomena pertinent to EDFALs and allows precise evaluation of behavior exhibited by EDFALs through a judicious selection of pump intensity and fiber length in standard eye-safe low-erbium concentration uniformly doped mono-mode silica glass fibers in co- and counter- propagating directions appropriate to signal, pump and ASE regimes.
关键词： analytical modeling,erbium-doped fiber amplifiers,optical fiber communication,erbium-doped fiber lasers
更新于2025-09-11 14:15:04
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Switchable Generation of Multipulse Patterns of Noise-Like Pulse and Dissipative Soliton Resonance in a Fiber Laser
摘要： We report on the switchable generation of versatile patterns of multiple noise-like pulse (NLP) and dissipative soliton resonance (DSR) pulses in a dual-pump figure-eight mode-locked fiber laser. Benefiting from the change of saturation power influenced by pump power intercoupling, harmonic DSR pulses, dual-pulse DSR, dual-pulse and tri-pulse NLP are formed depending on different pump power combinations and intra-cavity polarization states. We find that the NLP pulse profile can turn from h-shape to triangular-shape after splitting. The dual-wavelength spectrum of the pulse, consisting of an obvious stokes line, can tune its center from 1075 to 1097 nm. This type of fiber laser may be helpful for further in-depth study on the underlying dynamics of multiple NLP and DSR pulses.
关键词： mode-locked lasers.,Fiber lasers
更新于2025-09-11 14:15:04
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High energy noise-like pulse generation from a mode-locked thulium-doped fiber laser at 1.7-μm
摘要： Thulium-doped fiber laser (TDFL) is a versatile platform that can be engineered to produce laser sources with desired performance that target a vast number of applications, however its operation in the 1.7-μm region is still underdeveloped owing to the quasi-three-level nature of TDF emission. In this paper, we report a high energy noise-like pulse generation from a nonlinear polarization rotation (NPR) mode-locked TDFL. By using highly efficient core-pumping at 1650 nm and intra-cavity filtering component, stable mode-locking operation at 1750 nm is realized at a pump threshold of 1.5 W. With increasing the pump power to 5 W, the pulse width is stretched from 0.8 ns to 3.7 ns, while the monitored output power is linearly increased from 50 mW to 251 mW, corresponding to a maximum pulse energy of 321 nJ at the pulse repetition rate of 782 kHz. The long-term and shot-to-shot stability of the output are characterized to be 0.11 dB and 2.8% respectively. Noise-like pulse operation of the laser is confirmed by measuring the autocorrelation trace, which demonstrates a coherent peak on top of a wide pedestal. To the best of our knowledge, this is the first demonstration of high energy noise-like pulse generation from a TDFL at 1.7-μm band, enabling potential applications in for example spectroscopic analysis and material processing.
关键词： mode-locked lasers,Fiber lasers
更新于2025-09-11 14:15:04
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High Energy Ultrafast Laser at 2 μm Using Dispersion engineered Thulium-Doped Fiber
摘要： We report on demonstration of high energy pulse laser at 2 μm by employing a normal dispersion fiber attained by a waveguide dispersion engineering. The normal dispersion fiber has a W-type refractive index profile, with a Thulium(Tm)-doped core. In contrast to a strong anomalous dispersion at 2 μm in a step-index fiber, the design allows strong waveguide dispersion that can generate normal dispersion at the Tm emission band. Mode area scalability of this fiber is discussed under the normal dispersion requirement. The Tm-doped fiber (TDF) is deployed in a ring cavity to produce mode-locked pulses near 2 μm. Subsequently, the pulse is amplified with more than 27 dB gain through the normal dispersion TDF. The output pulse energy reaches up to ~525 nJ at 1852 nm without pulse breaking due to the engineered dispersion. The achieved pulse energy is record high for all-fiber configuration near 2 μm, to our knowledge.
关键词： dispersion shift,Fiber Lasers,Thulium,Specialty Fiber,Ultrashort Pulses
更新于2025-09-11 14:15:04
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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) - Photo Darkening Suppression in Highly Yb-Doped Aluminophosphosilicate Fiber by Addition of Cerium
摘要： Photodarkening (PD) suppressed low numerical aperture (NA), high absorption, low loss, large mode area (LMA) fiber is an important requirement for high power fiber lasers, in both pulsed and continuous wave operation regimes. We have reported the fabrication of high absorption (~1200 dB/m core absorption) Yb doped aluminophosphosilicate fiber with raised Ge cladding to realize low NA step index fiber [1]. The presence of Aluminium (Al) and phosphorus (P) in the core helps in lowering the PD loss by a significant margin, but some PD loss is still observed. In this work we intend to further lower the PD loss by adding Cerium (Ce) to this equimolar P:Al core. Previous reports suggests that addition of Ce to Yb:Al core significantly reduce the PD loss when the ratio of Ce oxide to Yb oxide ratio is ~0.5-0.7 [2-4]. However, like Yb, Ce has a high molar refractivity, and all dopants (Yb, Ce and Al) push up the core NA. In our work, equimolar P:Al does not contribute to index of the core, and only the Ce and Yb raise the core NA. Furthermore, the reported raised Ge cladding technique can compensate the core NA to a desired level [1]. We here present three fibers with high Yb concentration of ~0.5mol% and with equimolar Al and P composition, all fabricated by modified chemical vapor deposition and solution doping technique. Fiber #1 contains no Ce while Fiber #2 and Fiber #3 contain Ce with different Ce/Yb oxide ratio of ~0.24 and ~0.625, respectively. The index profiles of the three fibers are shown in Fig. 1(a). As expected, the core NA increases with Ce concentration. Compositional concentration profile in Fiber #3 measured by energy dispersive X-ray analysis (EDX) is shown in Fig. 1(b). P2O5, Al2O3, Yb2O3 and CeO2 were found to be around 5 mol%, 4.6 mol%, 0.48 mol% and 0.3 mol% respectively, in the core. Hence the Ce/ Yb oxide ratio was observed to be ~0.625, which according to the reported works is supposed to yield quite good PD suppression while creating no additional thermal issues. All the fibers have similar Yb, Al and P contents with only difference in the Ce concentration. Fiber#2 contains ~0.12mol% of Ce2O3. The background losses in the fibers were found to be <25dB/Km after a cut-back method measurement. This is considered low for fibers with such high Yb concentration. Finally, the fibers were tested for PD loss using core pumped configuration with 634 nm as a probe wavelength and 976 nm as pump wavelength. Population inversion levels of ~45% was maintained in all the fibers. The PD losses for the fibers are shown in Fig. 1(c). Fiber#1, Fiber #2 and Fiber#3 has PD losses of 70 dB/m, 30 dB/m and 7 dB/m respectively. Thus, it can be clearly seen that addition of Ce to Yb doped aluminophosphosilicate fiber reduces PD significantly, with the ratio of Ce:Yb playing a major role as well. In conclusion, we report the first fabrication of Ce and Yb doped aluminophosphosilicate fiber with very high absorption, and extremely low PD.
关键词： Aluminophosphosilicate fiber,Fiber lasers,Yb-doped,Photodarkening,Cerium
更新于2025-09-11 14:15:04
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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) - Tm-Doped Nonlinear Fiber Amplifier Emitting 50 fs Pulses and 20 W of Average Power at 2 μm Wavelength
摘要： Tm-doped fiber lasers with an emission wavelength around 2 μm have drawn increasing attention for applications in fundamental and life sciences. It has recently been identified, that the utilization of long wavelength drivers is beneficial for the parametric downconversion into the molecular fingerprint region (2-20 μm wavelength), since they can effectively use conveniently available non-oxide crystals with high conversion efficiency to address the wavelength region beyond 5 μm, which is difficult with today’s well matured 1 μm drivers. Transferring these results into an application driven context in medical and life sciences requires a compact design and flexibility of the driving source to serve a huge audience. Addressing the mid infrared fingerprint region via parametric downconversion requires both, short pulses and moderate peak power to ensure a good spectral coverage. To fulfill these requirements chirped pulse amplifiers use bulky post compression schemes, which makes them not well suited for this field of application. In this work we propose a nonlinear fiber amplifier, which has the potential to drastically shrink the footprint of the driving source, by combining both compression and amplification in a single fiber. This will ultimately enable for high-power shoebox size laser sources in the molecular fingerprint region.
关键词： molecular fingerprint region,nonlinear fiber amplifier,parametric downconversion,Tm-doped fiber lasers
更新于2025-09-11 14:15:04
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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) - Short-Wavelength, Near-Diffraction-Limited Beam, 792 nm Cladding Pumped Efficient Thulium-Doped Fiber Laser in a Power-Scalable Fiber Design
摘要： Thulium-doped fiber lasers (TDFLs) offer a broad 3F4 → 3H6 emission band ~1600-2200 nm. Thanks to “two-for-one” cross-relaxation process in TDFLs, that enables to achieve output power > 1 kW at ~2045 nm with 0.79-μm cladding-pumping. Efficient cross-relaxation requires high Tm-concentration ( > 3wt%). This results in a high core refractive index (thus higher V-number) that degrades the beam quality. It also increases the thermal load per unit length, although this can be reduced by a large cladding-to-core area ratio that increases the absorption length of the fiber. A long fiber also shifts the emission to long wavelengths with more signal re-absorption. For short-wavelength emission the re-absorption must be reduced in some other way, which also ensures adequate total pump absorption. Simplest technique is to reduce the area ratio, but then excessive thermal load or inefficient cross-relaxation (if the Tm-concentration is low to reduce the thermal load per unit length) hampers power-scaling.
关键词： short-wavelength,Thulium-doped fiber lasers,power-scalable fiber design,near-diffraction-limited beam
更新于2025-09-11 14:15:04
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Stability investigation of a multi-wavelength fiber linear cavity laser using a highly nonlinear fiber
摘要： A stable multi-wavelength fiber linear cavity laser based on cascaded four-wave mixing in a highly nonlinear fiber is proposed and experimentally demonstrated. In this scheme, the instability caused by model competition between comb filtering of the Sagnac interferometer loop mirror and self-seeded cascaded stimulated Brillouin scattering in the fiber cavity is successfully mitigated by the self-stability mechanism in the highly nonlinear fiber. Fifteen stable laser lines within 3 dB flatness are obtained at a pump power of 550 mW. We believe this can be further improved and the cavity structure further simplified by optimizing the design of the erbium-doped fiber and improving pump efficiency. However, stable multi-wavelength operation cannot be obtained by using a similar linear cavity structure. Therefore, the stability mechanism of multi-wavelength fiber linear cavity lasers using highly nonlinear fiber is investigated in detail.
关键词： fiber lasers,highly nonlinear fiber,nonlinear optics,four-wave mixing
更新于2025-09-11 14:15:04