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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) - Polarization Modulation Instability in All-Normal Dispersion Microstructured Optical Fibers with Quasi-Continuous 1064 nm Pump
摘要： Polarization modulation instability (PMI) is a form of modulation instability that can exist in weakly birefringent optical fibers. Sidebands can be generated by this effect when a polarization mode of the birefringent fiber is excited with an intense optical pump. The polarization state of the sidebands is orthogonal to the polarization of the pump signal. PMI has been observed in microstructured optical fibers (MOFs). PMI was reported in a large-air-filling fraction MOF that was pumped in the normal dispersion regime with visible light. The coherent degradation of femtosecond supercontinuum light generated in all-normal dispersion (ANDi) MOFs due to PMI was recently investigated. Here, we report the experimental observation of PMI effect in ANDi MOFs with picosecond pumping at 1064 nm.
关键词： Polarization modulation instability,microstructured optical fibers,picosecond pumping,all-normal dispersion
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) - A Functional Mapping for Passively Mode-Locked Semiconductor Lasers
摘要： Passive Mode-locking (PML) of semiconductor lasers is a most promising method for the generation of low repetition rate picosecond pulses, which is of paramount importance for a number of applications. Because of the long round-trip times and fast time scales of the ?eld evolution this regime is computationally very intensive. Studying the pulse train dynamics and temporal jitter can require simulations over hundreds of thousands of round-trips. If, in addition to the longitudinal dynamics, transverse diffraction of the beam or thermal processes are considered, the problem becomes intractable. The Haus master equation [1] is a widely used approach to study PML. By considering a partial differential equation (PDE) model one can restrict the analysis of the ?eld to a small temporal interval around the pulse, making the approach computationally ef?cient. Yet this method, when applied to a particular design, provides only qualitative predictions due to the many simplifying hypothesis involved. We present a method that combines the accuracy of ?rst principle time-delayed models with the computational ef?ciency of the Haus master equation. Our method is based upon computing only the so-called fast stage in the vicinity of the pulse where stimulated emission is dominant, while using an approximate analytical solution of the dynamics during the slow stages in-between pulses. We illustrate the idea of the functional mapping (FM) using the DDE model of [2] that considers unidirectional propagation in a ring laser, however it can be used in other models as well, including approaches using delay algebraic equations (DAEs) like [3]. The equations for the ?eld amplitude A, the gain G and the absorption Q read ˙A γ = ?A +Y (t ? τ) , ˙Q = Q0 ? Q ? s (cid:2) 1 ? e (cid:3) ?Q |A|2 , (1) (3) ˙G = Γ (G0 ? G) ? e ?Q (cid:2) eG ? 1 (cid:3) |A|2 , (2) (cid:4) Y (t) = √ κ exp 1 ? iα 2 G (t) ? 1 ? iβ 2 (cid:5) Q (t) A (t) . (4) We wrote Eq. (1) in a form that makes apparent that the forcing ?eld Y (t ? τ) de?ned in Eq. (4) is a nonlinear function that is known over a whole interval of duration τ. Since gain G and losses Q are functions of A, Y involves only the past values of the ?eld, i.e., Y (t ? τ) = g [A (t ? τ)]. Knowing the forcing term Y, Eq. (1) can be solved for A over an interval of duration τ. Integrating Eqs. (1-4), not over the whole round-trips, but only in a selected time interval in the pulse vicinity, is at the core of the functional mapping (FM) method. The speedup of the FM is equal to the ratio of the actual integration domain 2δ and of the full round-trip τ, i.e., m = τ/ (2δ ). Taking a domain of duration 2δ = 5τp, a pulse with of τp = 1 ps at a repetition rate of τ ?1 = 1 GHz, yields a speedup m = 200, i.e., a 24 hours simulation with, e.g., slow thermal effects or transverse diffraction could potentially be achieved in a few (～ 7) minutes.
关键词： picosecond pulses,semiconductor lasers,Passive Mode-locking,computational efficiency,functional mapping
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) - Passively Mode-Locked High-Repetition Rate Er:YLF Laser at 2.81 μm Generating 72 ps Pulses
摘要： The erbium-doped active media allow to generate laser radiation in spectral range 2.7-2.94 μm if the laser transition 4I11/2→4I13/2 is used. Since the laser radiation in this spectral range is strongly absorbed in the water these lasers can be used in medicine (surgery, ophthalmology, urology). Nowadays, there are many papers deal with erbium-doped bulk active media operating in free-running or Q-switched regime, nevertheless, the passively mode-locked lasers are mainly built with Er-doped fibres. However, the compact passively mode-locked erbium-doped bulk lasers could offer a higher repetition rate and smaller dimensions. To date, the shortest laser pulses (1.78 ns) generated with erbium bulk laser (Er:CaF2-SrF2) was obtained in Q-switched mode-locked regime. In this paper, the SESAM mode-locked compact Er:YLF laser with the picosecond pulses and GHz repetition rate for the first time, according to the author’s knowledge, is presented.
关键词： mode-locked,GHz repetition rate,picosecond pulses,laser,erbium-doped
更新于2025-09-11 14:15:04
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An insight into laser tattoo removal: reasoning, methods and limitations
摘要： This article aims to review the possible reasons a patient may wish to remove their tattoo using lasers, as well as providing an overview of the tattooing process within the skin, where the tattoo ink particles lay within the skin’s structures and how lasers specifically target unwanted ink particles within the skin. An exploration into various tattoo removal methods, with a more in-depth focus on laser tattoo removal with its associated risks and limitations will also be addressed.
关键词： Hyperpigmentation,Photothermolysis,Q-switched lasers,Tattoo removal,Hypopigmentation,Picosecond lasers
更新于2025-09-11 14:15:04
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Crafting Interior Holes on Chemically Strengthened Thin Glass Based on Ultrafast Laser Ablation and Thermo-Shock Crack Propagations
摘要： To prevent glass cracking from external mechanical damages, chemically strengthened glass is usually employed. The cutting of strengthened glass becomes critical due to their residual tensile stress induced in the inner core of the display unit of mobile communication and computational devices. This method integrates picosecond laser ablation with quenching induced thermo-shock for accomplishing such a task. Essential analyses are performed based on fracture mechanics and finite element method to provide the scientific basis of such an approach. Experimental results indicate that with a proper temperature control, the proposed method could achieve successful separations for various enclosed shapes with the associated surface roughness satisfying the requirement.
关键词： thermo-shock,Glass,picosecond laser ablation,Packaging
更新于2025-09-11 14:15:04
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The Role of the Surface Nano-Roughness on the Wettability Performance of Microstructured Metallic Surface Using Direct Laser Interference Patterning
摘要： Superhydrophobic natural surfaces usually have multiple levels of structure hierarchy, particularly microstructures covered with nano-roughness. The multi-scale nature of such a surface reduces the wetting of water and oils, and supports self-cleaning properties. In this work, in order to broaden our understanding of the wetting properties of technical surfaces, biomimetic surface patterns were fabricated on stainless steel with single and multi-scale periodic structures using direct laser interference patterning (DLIP). Micropillars with a spatial period of 5.5 μm and a structural depth of 4.2 μm were fabricated and covered by a sub-micro roughness by using ultrashort laser pulses, thus obtaining a hierarchical geometry. In order to distinguish the influence of the different features on the wettability behavior, a nanosecond laser source was used to melt the nano-roughness, and thus to obtain single-scale patterns. Then, a systematic comparison between the single- and multi-scale structures was performed. Although, the treated surfaces showed hydrophilic behavior directly after the laser treatment, over time they reached a steady-state hydrophobic condition. However, the multi-scale structured metal showed a contact angle 31° higher than the single-scale geometry when the steady-state conditions were reached. Furthermore, the impact of the surface chemistry was investigated by energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) analyses. Finally, a hydrophobizing agent was applied to the laser treated samples in order to further enhance the water contact angles and to determine the pure contribution of the surface topography. In the latter case, the multi-scale periodic microstructures reached static contact angles of 152° ± 2° and a contact angle hysteresis of only 4° ± 2°, while the single-scale structures did not show superhydrophobic behavior. These results definitely suggest that multi-scale DLIP structures in conjunction with a surface chemistry modification can promote a superhydrophobic regime.
关键词： multi-scale microstructures,wettability transition,nanosecond and picosecond laser pulses,direct laser interference patterning
更新于2025-09-11 14:15:04
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Metal ablation study with a 10 picosecond laser under low and median fluence
摘要： Single shot 10 ps laser ablation on aluminium and gold at a wavelength of 1064 nm under low and median laser fluence was studied theoretically and experimentally. Simulations have been performed by using an optimized two temperature model. It is revealed that electron-phonon coupling ability of the target metal affected both the ablation depth and target metal’s morphology. Under low fluence, melting could well be the relevant ablation mechanism. With laser fluence rising, vaporization or phase explosion happens thereafter, depending on material’s electron-phonon coupling ability.
关键词： Metals and alloys,Picosecond laser processing,Modeling of laser ablation
更新于2025-09-11 14:15:04
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Versatile high power pulse-laser source for pico- and nanosecond optical pulses
摘要： This paper presents a pulse-laser source for the generation of ps and ns laser pulses with more than 50 W peak output power. The final stages of the drivers use GaN transistors and are capable of switching currents of 0.8 A with 200 ps minimum pulse width and 50 A with 3 ns minimum pulse width. The pulses can be externally triggered by ECL logic. Both single-pulse and pulse train modes are possible.
关键词： fast current driver,GaN HEMT,optical pulse gating,Picosecond laser source
更新于2025-09-11 14:15:04
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One-step P2 scribing of organometal halide perovskite solar cells by picosecond laser of visible wavelength
摘要： Perovskite solar cells (PSC) have attracted attention by its unprecedented rise in device efficiency. However, the PSCs were mostly tested for the unit cell of small area, and it is important to upscale to solar modules. Laser scribing has great potential to this end. However, the key challenge identified in one-step P2 laser scribing is to remove film stack including the hole block layer (HBL) without damaging transparent conducting oxide (TCO) based bottom contact and thus to provide interconnecting paths with minimized contact resistance. In this study, we evaluate one-step P2 scribing performance of picosecond laser of 532 nm wavelength for mesoscopic perovskite architecture with the c-TiO2 as the HBL and fluorine doped tin oxide (FTO) as bottom contact. Despite anticipated challenge of low absorption selectivity, c-TiO2 layer could be efficiently removed without FTO damage over wide processing window enabling a self-terminating mechanism. Detailed parametric studies elucidate relevant scribing mechanisms such as layer-by-layer ablation mechanism or lift-off mechanism depending laser illumination direction. It is also revealed that the removal of c-TiO2 is triggered by ablation of upper layers, in particular, the mesoporous TiO2. Module level test is under way in conjunction with investigation of further scribing mechanisms.
关键词： picosecond laser,P2 scribing,laser scribing,Perovskite thin film solar cell
更新于2025-09-11 14:15:04
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Resonance Enhancement in Laser-Produced Plasmas (Concepts and Applications) || Resonance Processes at Different Conditions of Harmonic Generation in Laser-Produced Plasmas
摘要： Resonance Processes at Different Conditions of Harmonic Generation in Laser-Produced Plasmas
关键词： resonance enhancement,laser-produced plasmas,picosecond pulses,high-order harmonic generation,harmonic generation
更新于2025-09-11 14:15:04