- 标题
- 摘要
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - High-Power Ultrafast Industrial Thin-Disk Lasers
摘要： Ultrafast amplifiers using industrial thin-disk technology from TRUMPF deliver record pulse energies of 200 mJ at 5 kHz. In addition, multipass amplifiers to increase the average power and pulse energy and concepts for nonlinear compression to reach pulse durations below 50 fs will be discussed.
关键词： diode-pumped,ultrafast,high-energy,Thin-disk laser,amplification,high-power,laser amplifier,X-ray
更新于2025-09-11 14:15:04
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Analysis and design of TEM-TE11 coaxial waveguide bend mode converters
摘要： Two coaxial waveguide bend mode converters that transform coaxial transverse electromagnetic mode to TE11 coaxial waveguide mode are presented in this paper. Both converters are designed and optimized on the basis of the strictly derived mode coupling coefficients. Conversion efficiencies of both converters are over 99% and the power-handling capacities reach a gigawatt level. The combined dual-bend mode converter is fabricated and tested. The experimental results coincide well with the theoretical calculations and simulations, which demonstrates the feasibility of the designed converter.
关键词： Mode converter,high-power microwave,waveguide bend,mode coupling
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) - Up-Scaling the Power of Pulsed Single Frequency Fibre Amplifiers for Coherent LIDAR Applications
摘要： In optical sensing applications, the laser sources are strongly constrained by the sensing system requirements. In the case of coherent LIDARs, that measure wind speed thanks to the Doppler shift (by means of a coherent detection), highly coherent high power pulsed lasers with good output beam quality are necessary to guarantee a proper measurement over long distances. The pulsed emission ensures the spatial resolution along the line of sight whereas the high coherence accounts for the wind speed resolution (measured in the frequency domain). Thus, the challenge when designing laser sources for such instruments resides in the difficulty of improving the output power while not altering the other characteristics. Fibre lasers and amplifiers have proven their interest in high power laser systems thanks to their compactness and their stability against temperature and mechanical fluctuations. The increase of emitted optical power is currently limited by nonlinear effects due to the intrinsically high confinement of the optical field in fibres. Among all the nonlinear effects, the Stimulated Brillouin Scattering (SBS) predominates in the case of single frequency or narrow spectrum optical fields. In order to increase the power of single frequency fibre lasers, many developments have been done in the past decades to mitigate SBS. We can class the different SBS mitigation techniques in two categories depending on whether they act on the optical field properties or on the optical fibre itself. All the techniques belonging to the first category are based on an active control of the phase or the frequency of the incident optical wave, in order to spread the incident energy in the spectral domain. In the second category, we can maximize the core radius of the fibre, minimize the fibre length, apply temperature gradients, dopant concentrations gradients or strain gradients to broaden the SBS spectrum in a controlled manner and thus lower its effective gain. We review here the different techniques we use to mitigate the SBS in pulsed single frequency fibre amplifiers and discuss their conceptual and technical limitations. Among all the existing mitigation techniques, we present here different realizations of fibre amplifiers designed for coherent LIDAR systems, based on strain gradients [1] and specifically designed highly doped and large core active fibres [2]. Figure 1 presents the typical achievements obtained with our patented tensile and compressive strain gradients techniques when applied to active fibers. We are able to increase the output power by a factor 2 to 3 while keeping a high beam quality on a highly coherent laser emission. We emphasize the robustness of such developments thanks to the absence of active devices that make them suitable for embedded sensing applications.
关键词： coherent LIDAR,high power pulsed lasers,Stimulated Brillouin Scattering,SBS mitigation,single frequency fibre amplifiers
更新于2025-09-11 14:15:04
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High-Power Large-Energy Rectangular Mode-Locked Er-Doped Fiber Laser Based on High-Damage-Threshold MoS <sub/>2</sub> Saturable Absorber
摘要： In our work, based on chemical vapor deposition method and a newly designed glass–material–glass sandwich structure, MoS2 saturable absorber (SA) with a damage threshold of higher than 0.26 J/cm2 was fabricated and employed for demonstrating high-power, large-energy rectangular mode-locked Er-doped laser operation. Stable mode-locked operation with maximum output power of 122.77 mW and largest pulse energy of 130.49 nJ were successively achieved along with power scaling process. In comparison with previous works, our results show remarkable breakthroughs both in the aspects of average output power and pulse energy. Our experimental design and results will open a new avenue for generating high-power, large-energy mode-locked ?ber lasers based on two-dimensional materials as SAs.
关键词： Chemical vapor deposition,new-designed glass-material-glass sandwich structure,high-power mode-locked ?ber laser
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) - All-Fiber High-Average-Power 4.42-μm Raman Laser Based on Silica Fiber
摘要： Mid-infrared lasers operating at wavelengths above ~3 μm are required for many applications. The lasers of a particular interest are those that can provide high average power and high quality of the output beam. A promising approach to realize such lasers is the use of gas-filled hollow-core fibers (HCF), which combine mid-infrared light guidance with all the advantages of well-established silica fiber technology. Recent progress in silica HCFs for mid-infrared spectral range has resulted in demonstration of various gas fiber lasers at wavelengths from 2.8 to 4.6 μm [1-5]. However, those lasers use bulk elements to couple the pump into a HCF, thus losing such advantages as compactness and alignment-free operation, which are expected from fiber lasers. In this work we demonstrate an all-fiber gas Raman laser operating in a single transversal mode at 4.42 μm and generating average output power as high as 360 mW. The Raman laser was constructed using silica-based fibers only (Fig.1a). A pump source was a high-power erbium-doped fiber laser emitting 2-ns pulses with 75-kHz repetition rate at 1.56 μm. The output fiber of the pump laser was fusion spliced to a revolver-type HCF. In spite of a large difference in mode field diameters of the solid-core and hollow-core fibers (20 and 55 μm, respectively), a 3-dB splice losses were obtained. The splice point was mechanically stable and no splice loss degradation was observed when HCF was filled by molecular hydrogen up to pressure of 50 atm. By using a 3.2-m-long hydrogen-filled revolver-type HCF we realized an efficient 1.56 to 4.42 μm Raman conversion in a single-pass single-cascade scheme. When 2.3 W of the pump average power was coupled to the HCF, the Raman laser generated as high as 360 mW of average power at 4.42 μm (Fig.1b). The quantum conversion efficiency was as high as 46 %. A beam quality factor of the output radiation at λ=4.42 μm was evaluated to be M2=1.4. Our results demonstrate that gas fiber Raman lasers based on revolver hollow-core silica fibers are a viable solution for the development of all-fiber mid-infrared lasers that combine a compact alignment-free design with high power single mode operation. An application area of such laser sources includes, but is not limited to, a high-average-power mid-infrared supercontinuum generation, which is of high importance for numerous applications in science, biomedicine and technology.
关键词： gas-filled hollow-core fibers,silica fiber,mid-infrared lasers,Raman laser,high power
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) - High-Power Dual-Comb Thin-Disk Oscillator
摘要： Dual-comb spectroscopy is a rapidly advancing spectrometric technique where the temporal interferograms generated with two asynchronous trains of pulses are recorded, and Fourier transformed to reveal the spectrum of an absorber in the beam path [1]. To date, best performance is achieved with systems involving complex active stabilization of two femtosecond erbium fiber lasers [1]. One way to simplify the technique is to generate a dual-comb output from a single laser cavity. However, there have been only a few demonstrations of such a scheme so far [2,3]. Here we present a dual-comb system based on a single thin-disk oscillator. The novel architecture effectively rejects common noise, with mutual coherence time exceeding one second without any active stabilization. Moreover, the system shows nearly an order of magnitude higher average and peak output powers compared to previous dual-comb demonstrations. Efficient nonlinear frequency conversion to the UV or mid-IR regions—of high interest to molecular spectroscopy—will thus be greatly facilitated.
关键词： thin-disk oscillator,high-power,Yb:YAG,Kerr-lens mode-locked,dual-comb spectroscopy
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) - Pulsed Yb-Doped Phospho-Silicate Fiber MOPA Source with 25kW Peak Power and Excellent Beam Quality
摘要： With ytterbium doped fiber (YDF) lasers and amplifiers have reached continuous wave output power of multi-kW with direct diode pumping [1] and 10kW with tandem pumping [2] in a good beam quality, today fiber lasers are becoming the laser choice for many industrial applications and processes, defense, and scientific research. One of the challenges of high average power fiber laser is to maintain a long-term stability of the output power. In particular, photodarkening (PD) is seen as a power loss in YDF gain medium that can significantly influence the operation lifetime of the device. Moreover, it was observed that the PD is related to the transverse mode instability (TMI) that can limit the output power of the laser [3]. In silica host, co-dopant phosphorous (P) is more effective than aluminium (Al) to suppress the PD effect in YDF. In addition, Yb-doped phosphosilicate (Yb-PS) fiber is found suitable for high power laser operation below 1020nm [4]. Such lasers are used as pumps in tandem pumping to reduce the heat load associated with the quantum defects in YDF lasers operating at 10kW level [4]. However, Yb-PS fiber are generally considered difficult to fabricate due to evaporation of P2O5 during the preform fabrication process, resulting in a central dip in the core refractive index profile that has detrimental effect on the output beam quality of fiber lasers. Other disadvantage of P co-doping is its smaller Yb - absorption and emission cross-sections compared to Al counterpart. To compensate for the cross-sections, higher concentrations of Yb and P (to prevent Yb ions from clustering) are needed in fiber. This contributes to a high core NA and poses a challenge to fabricate a large mode area Yb-PS fiber. Here we report an efficient Yb-PS high power laser fiber fabricated using an optimized MCVD (modified chemical vapor deposition) and all-vapor-phase chelate precursor doping technique. Double-clad fiber with a 150μm quasi-octagonal inner cladding and a 12μm core diameter was drawn with a low index polymer outer cladding. The core NA was 0.1, Fig.1 (a). The small signal absorption at the pump wavelength of ~976nm was measured as 2.5 dB/m. Initially the fiber was tested in a 4%-4% laser cavity. An output power of >100W (limited by the available pump power) and the slope efficiency of >85% were obtained. The laser emission was centered at 1066nm. We then tested the same fiber in a pico-second MOPA configuration. Fig. 1(b) shows the experimental schematic. A 4m long Yb-PS fiber was used in the final stage of the MOPA. A gain-switched diode operating at ~1035nm with 180ps pulse width and 2.95MHz repetition rate was used as a seed laser. Fig. 1(c) shows the average signal output power with respect to the absorbed pump power in the final stage of the amplifier. The output power reached 13.3W and the slope efficiency was 74%. The corresponding pulse energy and peak power was 4.5μJ and 25kW respectively. The measured beam quality (M2) was ~ 1.13, as shown in inset of Fig. 1(c). The spectra of the seed laser and at the maximum signal output power are shown in Fig. 1(d). The 3dB spectral bandwidth at the maximum output power was measured as 0.29nm compared to 0.03nm of the seed laser. The magnitude of the stimulated Raman scattering (SRS) appeared at a wavelength of ~1080nm was 30dB lower than the output signal – see Fig. 1(d). In conclusion, we have demonstrated that an all-vapor-phase chelate doping technique holds great potential to fabricate LMA Yb-doped phosphosilicate fibers with diffraction limited beam for high power lasers.
关键词： high power laser,Yb-doped phosphosilicate fiber,photodarkening,all-vapor-phase chelate precursor doping,transverse mode instability,MCVD
更新于2025-09-11 14:15:04
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AIP Conference Proceedings [AIP Publishing LLC EXOTIC NUCLEI AND NUCLEAR/PARTICLE ASTROPHYSICS (V). FROM NUCLEI TO STARS: Carpathian Summer School of Physics 2014 - Sinaia, Romania (13–26 July 2014)] - Perspectives for neutron and gamma spectroscopy in high power laser driven experiments at ELI-NP
摘要： The measurement of energy spectra of neutrons and gamma rays emitted by nuclei, together with charge particles spectroscopy, are the main tools for understanding nuclear phenomena occurring also in high power laser driven experiments. However, the large number of particles emitted in a very short time, in particular the strong X-rays flash produced in laser-target interaction, impose adaptation of technique currently used in nuclear physics experiment at accelerator based facilities. These aspects are discussed (Section 1) in the context of proposed studies at high power laser system of ELI-NP. Preliminary results from two experiments performed at Titan (LLNL) and ELFIE (LULI) facilities using plastic scintillators for neutron detection (Section 2) and LaBr3(Ce) scintillators for gamma detection (Section 3) are presented demonstrating the capabilities and the limitations of the employed methods. Possible improvements of these spectroscopic methods and their proposed implementation at ELI-NP will be discussed as well in the last section.
关键词： gamma spectroscopy,neutron spectroscopy,nuclear physics,ELI-NP,high power laser
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) - High-Power Short-Wavelength Infrared Supercontinuum Generation in a Multimode Fluoride Fiber
摘要： Supercontinuum light (SC) is a broadband source with unique properties generated via cascaded nonlinear processes when intense light propagates in a nonlinear material. Depending on the nonlinear material and pump source used, the spectrum of a SC source can span from the visible to the mid-infrared with up to several Watt-average power. Recently, the generation of broadband SC sources operating in the mid-infrared (MIR) has attracted significant interest due to a wide range of potential applications in spectroscopy, microscopy, molecular fingerprinting, environmental monitoring and LIDAR. Fibers made of non-silica soft glasses such as fluoride, tellurite and chalcogenide are good candidates for SC generation in the MIR due to their high intrinsic nonlinearity and wide transparency window in this wavelength range. To date, most of supercontinuum sources demonstrated in the mid-infrared have been generated in single mode soft glass fibers that cannot sustain high level of average power due to their small core size and low damage threshold. This generally imposes a limit on the maximum output power which can be a limitation for practical applications, especially in long-distance remote sensing for which high power is key. In order to overcome this problem, multimode fibers with large core size and higher damage threshold are a promising alternative. Here, we demonstrate for the first time the generation of an octave-spanning SC by injecting 1 MHz, 350 fs pulses from an optical parametric amplifier in a meter-long multimode step-index InF3 fiber with 100 μm core diameter. We performed a systematic study of the SC spectrum as a function of the pump wavelength and the largest SC spectrum spanning from 1100 nm to 2500 nm with 600 mW output power was generated when injecting the pulses at 1960 nm, in the anomalous dispersion regime of the fundamental mode. The output beam profile of the SC was characterized in different wavelengths bands, illustrating the highly multimode nature of the SC generation process. Numerical simulation results shows that higher-order soliton dynamics and dispersive wave generation in multiple higher-order modes are key contributions to reaching octave-spanning bandwidth in a fiber with large core size. Our results open up a promising route towards ultra-high power broadband sources in the MIR for applications where a single-mode spatial intensity distribution is not essential such as e.g. in remote sensing.
关键词： mid-infrared,high-power,fluoride fibers,multimode fibers,Supercontinuum generation
更新于2025-09-11 14:15:04
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Optimized uni-traveling carrier photodiode and mushroom-mesa structure for high-power and sub-terahertz bandwidth under zero- and low-bias operation
摘要： In this paper, physically-based simulations are carried out to investigate and design uni-traveling carrier photodiode (UTC-PD) for high-power sub-terahertz wave generation at zero- and low-bias operation. The reliability of the physically-based simulation is demonstrated by comparing with our experimental result. Both the bandwidth and RF output power of the proposed UTC-PD is significantly improved by careful design the built-in electric field distribution under high-power input. For the optimized UTC-PD with the mesa diameter of 5 μm, its 3dB bandwidth large than 100 GHz even if the photocurrent reaches 6 mA under zero-bias operation. The device can reach a high bandwidth of 92.4 GHz, 105 GHz, and 119.5 GHz under the reverse bias of 0.5 V, 1 V, and 2 V, respectively, even the input photocurrent as high as 18.2 mA. The peak output-power of the device has enhanced at least 7 dB even at 170 GHz and zero- or low-bias operation. Besides, a novel design of mushroom-mesa UTC-PD (MM-UTC-PD) is proposed which with 4.3% improved high-speed performance. The MM-UTC-PD can trade-off between the external quantum-efficiency and bandwidth when miniaturized junction size is required.
关键词： ultrafast optics,sub-terahertz,optical communications,high-power photodiodes,optical receivers
更新于2025-09-11 14:15:04