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- 实验方案
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Suppression of amplitude modulation induced by polarization mode dispersion using a multi-degree-of-freedom fiber filter
摘要： Polarization mode dispersion (PMD) in ?bers for high-power lasers can induce signi?cant frequency modulation to amplitude modulation (FM-to-AM) conversion. However, existing techniques are not suf?ciently ?exible to achieve ef?cient compensation for such FM-to-AM conversion. By analyzing the nonuniform transmission spectrum caused by PMD, we found that the large-scale envelope of the transmission spectrum has more serious impacts on the amount of AM. In order to suppress the PMD-induced FM-to-AM conversion, we propose a novel tunable spectral ?lter with multiple degrees of freedom based on a half-wave plate, a nematic liquid crystal, and an axis-rotated polarization-maintaining ?ber. Peak wavelength, free spectral range (FSR), and modulation depth of the ?lter are decoupled and can be controlled independently, which is veri?ed through both simulations and experiments. The ?lter is utilized to compensate for the PMD-induced FM-to-AM conversion in the front end of a high-power laser facility. The results indicate that, for a pulse with phase-modulation frequency of 22.82 GHz, the FM-to-AM conversion could be reduced from 18% to 3.2% within a short time and maintained below 6.5% for 3 h. The proposed ?lter is also promising for other applications that require ?exible spectral control such as high-speed channel selection in optical communication networks.
关键词： laser facility,laser systems,optimization,high-power laser,laser facility and engineering,advanced laser technology and applications,?ber laser and applications,modeling,design
更新于2025-09-23 15:21:01
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Survey and technological analysis of laser and its defense applications
摘要： The laser technology has made remarkable progress over the past couple of decades. It is being widely employed in diverse domains, such as holography, space sciences, spectroscopy, medical sciences, micro and power electronics, industrial engineering, and most distinctively, as directed energy military weapons. Owing to their active transmissions, laser systems are similar to microwave radars to some extent; however, unlike conventional radars, the laser operates at very high frequencies thus making it a potent enabler of narrow-beam and high energy aerial deployments, both in offensive and defensive roles. In modern avionics systems, laser target indicators and beam riders are the most common devices that are used to direct the Laser Guided Weapons (LGW) accurately to the ground targets. Additionally, compact size and outstanding angular resolution of laser-based systems motivate their use for drones and unmanned aerial applications. Moreover, the narrow-beam divergence of laser emissions offers a low probability of intercept, making it a suitable contender for secure transmissions and safety-critical operations. Furthermore, the developments in space sciences and laser technology have given synergistic potential outcomes to use laser systems in space operations. This paper comprehensively reviews laser applications and projects for strategic defense actions on the ground or in space. Additionally, a detailed analysis has been done on recent advancements of the laser technology for target indicators and range-finders. It also reviews the advancements in the field of laser communications for surveillance, its earlier state of the art, and ongoing scientific research and advancements in the domain of high energy directed laser weapons that have revolutionized the evolving military battlefield. Besides offering a comprehensive taxonomy, the paper also critically analyzes some of the recent contributions in the associated domains.
关键词： Survey,Non-lethal Weapons,Taxonomy,Laser Military Projects,Laser Military Applications,Directed Energy Weapons,Laser Systems
更新于2025-09-23 15:19:57
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Discovery of Several New Families of Saturable Absorbers for Ultrashort Pulsed Laser Systems
摘要： Saturable Absorber (SA) is a key element of any passive mode-locked laser system to provide ultrashort laser system. So far various materials have been proposed that could be used for this purpose. However, the field is still looking for new ways to make the fabrication process easier and cost-effective. Another challenge in testing mode-locked laser systems using various SA samples is the lack of knowledge in preparing these by laser physicists given this is outside their remit of expertise. In this study, we have proposed a novel method to produce these SAs from plastic materials and glycol. Our new method relies upon increase in thickness up to a value where the modulation depth is enough to give stable ultrashort pulses. Although we have shown this method for four materials; similar approach could be applied to any material. this will open the door of unlimited families of SAs that could be easily prepared and applied without any prior knowledge in material sciences.
关键词： Mode-locked laser,Glycol,Plastic materials,Saturable Absorber,Ultrashort pulsed Laser Systems
更新于2025-09-23 15:19:57
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Tapered erbium-doped fibre laser system delivering 10 MW of peak power
摘要： We consider a fibre laser system generating ~10-mJ, ~500-fs pulses with a peak power of ~10 MW at a repetition rate of 100 kHz and emission wavelength of 1.56 mm. The system is based on a master oscillator – power amplifier configuration. The amplifier ensures chirped-pulse amplification. The pulses are then compressed by a dispersive grating compressor. The output amplifier stage is based on a specially designed tapered large mode area erbium-doped fibre for suppressing nonlinear effects. The experimental data agree with numerical simulation results for the stretcher, amplifier and compressor. The stretcher and amplifier have been simulated using a generalised nonlinear Schr?dinger equation. In addition, numerical simulation results suggest that optimising the stretcher and compressor will potentially allow the peak power of the system to be scaled up to ~30 MW.
关键词： erbium-doped fibre amplifiers,tapered fibre,dispersive grating compressor,high peak power fibre laser systems,chirped-pulse amplification
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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[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) - Dual Function Thin Slab Ultrafast Amplifier Producing 240W over a Range of Pulse Repetition Frequencies
摘要： Applications for ultrashort pulse (<100ps) laser systems are developing at an increasing rate. Broadly, the applications can be categorized as (a) low pulse repetition frequency (PRF) <1MHz, athermal machining with moderate pulse energies, and (b) high PRF, >1MHz highly localized (and controlled) melting with lower pulse energies. Ideally, a single technology platform should address the entire range of applications whilst providing the necessary average power to achieve productivity targets. Fibre based systems are ideally suited for average power scaling beyond the kilowatt level whilst maintaining excellent beam quality, although peak powers and pulse energies are limited by non-linear effects [1]. Therefore, bulk systems with carefully designed thermal management, such as thin disks, thin slabs and single crystal fibres have become dominant technologies for power and energy scaling of ultrashort pulse systems [2-5]. However, these configurations can result in limitations in frequency, power or energy. This paper reports results obtained for a single crystal thin slab amplifier configured in a novel integrated pre-amplifier/power-amplifier architecture that overcomes many of the limitations of the alternative technologies whilst creating a more compact device [6]. The output power is essentially independent of seed power, and pulse-picked PRF, for a significant range of frequencies, provided pulse energy damage thresholds are not exceeded.
关键词： ultrashort pulse,pulse repetition frequency,laser systems,thin slab amplifier,Yb:YAG
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) - Shaping of Picosecond Pump Pulses by SHG Depletion for Wide-Bandwidth TW-Class NOPCPA
摘要： On a global scale, great efforts were made to create TW-class laser systems based on an Optical Parametric Chirped Pulse Amplifier (OPCPA). The generation of stable white light supercontinuum (WLC) in the wavelength range from ~ 500 nm to ~ 1000 nm with picosecond pump pulses simplifies the OPCPA architecture due to the inherent signal and pump synchronization. In the OPA process, the resulting gain depends on the temporal profile of the pump pulse. For strongly chirped signal pulses, the amplification process may possibly lead to a significant decrease in the spectral bandwidth. This problem can be avoided by controlling the temporal shape of the pump pulse. We demonstrate the compact TW-class VIS-IR wavelength range NOPCPA with an almost lossless spectral bandwidth achieved due to the formation of “M”-shaped ps pumping pulses after the SHG-conversion. Moreover, the reuse of depleted pump pulses after some SHG and NOPA stages provides an increase in the overall pump-to-signal energy conversion efficiency.
关键词： TW-class laser systems,white light supercontinuum,SHG-conversion,picosecond pump pulses,Optical Parametric Chirped Pulse Amplifier,NOPCPA
更新于2025-09-12 10:27:22
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High power all-fiberized and narrow-bandwidth MOPA system by tandem pumping strategy for thermally induced mode instability suppression
摘要： An all-?berized and narrow-bandwidth master oscillator power ampli?cation (MOPA) system with record output power of 4 kW level and slope ef?ciency of 78% is demonstrated. Tandem pumping strategy is tentatively introduced into the narrow-bandwidth MOPA system for thermally induced mode instability (TMI) suppression. The stimulated Brillouin scattering (SBS) effect is balanced by simply using one-stage phase modulation technique. With different phase modulation signals, SBS limited output powers of 336 W, 1.2 kW and 3.94 kW are respectively achieved with spectral bandwidths accounting for 90% power of ～0.025, 0.17 and ～0.89 nm. Compared with our previous 976 nm pumping system, TMI threshold is overall boosted to be >5 times in which tandem pumping increases the TMI threshold of >3 times. The beam quality (M 2 factor) of the output laser is well within 1.5 below the TMI threshold while it is ultimately saturated to be 1.86 with the in?uence of TMI at maximal output power. Except for SBS and TMI, stimulated Raman scattering (SRS) effect will be another challenge for further power scaling. In such a high power MOPA system, multi-detrimental effects (SBS, SRS and TMI) will coexist and may be mutual-coupled, which could provide a well platform for further comprehensively investigating and optimizing the high power, narrow-bandwidth ?ber ampli?ers.
关键词： optimization,design,laser ampli?ers,narrow linewidth,high power laser,laser systems,modeling,advanced laser technology and applications,?ber laser and applications
更新于2025-09-10 09:29:36