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- 实验方案
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All-Optical Transmission Modulation Due to Inelastic Interactions of Ultrashort Pulses in a Disordered Resonant Medium
摘要： Random resonant media being one of the possible realizations of disordered metamaterials open a room of opportunities for achieving new fundamental effects and designing advanced nanophotonic devices. Strongly nonlinear optical properties of such media attract ever increasing attention nowadays from both theoretical and experimental points of view. Hereinafter, the case of the photonic-crystal-like structure with a randomly varying light–matter coupling provided by the random density of quantum particles is considered. Using numerical solution of the Maxwell–Bloch equations, the effects of the pulse collisions in the medium are studied. It is shown that disorder enables the qualitative changes of the system’s response for co-propagating pulses, whereas this is not the case for the counter-propagating ones. The scheme for an all-optical transmission modulation due to the disorder-induced inelasticity of collisions of co-propagating pulses is proposed. The ability of precise tuning the modulation via the inter-pulse distance and background refractive index adjustment is revealed. This novel approach for light control can be utilized for some high demand applications, such as modulation and switching of a pulsed radiation.
关键词： disordered metamaterials,transmission modulation,ultrashort pulses,localization of light,resonant medium
更新于2025-09-23 15:22:29
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[Laser Institute of America ICALEO?? 2016: 35th International Congress on Applications of Lasers & Electro-Optics - San Diego, California, USA (October 16a??20, 2016)] International Congress on Applications of Lasers & Electro-Optics - Enhanced drilling of transparent materials with ultrashort pulses
摘要： Ablative processes for transparent materials processing still remains a hot topic, as current techniques still have their limitations in ablation rates and quality, particularly for features on the order of a millimeter or less. In this publication, we present results of recent work on laser micromachining of sapphire with ultrashort pulsed lasers in the sub-picosecond regime. We accomplish this by using bottom-up processing with laser ablation, which has demonstrated the ability to generate zero-taper features with relatively high aspect ratios (>1:1) in many transparent materials. In previous work with <1ps (1030nm) sources, we have demonstrated the ability to drill ≤250μm diameter holes in 430μm thick c-plane sapphire. Here, we extend the scope of this work to examine additional methods and laser parameters presented here. In particular we examine the benefits of frequency conversion to 515nm wavelength, allowing smaller spots and higher fluence levels is compared to trials at the fundamental wavelength. We find no compelling differences in minimum achievable taper or drilling time for processes with 1030nm vs. 515nm performed with similar fluences, but the smaller spot size and increased fluence afforded with 515nm light allows for faster bottom-up drilling. Additionally, we test the effects of water-assisted processing by placing the sapphire wafer in contact with a water bath for better extraction of particulate matter during processing. Processes with a water bath are found to allow holes with 2° taper to be drilled in ≤5 seconds, which is a decrease in cycle time of ≥50% for holes with ≤2° taper in air.
关键词： laser micromachining,bottom-up processing,sapphire,ultrashort pulses,water-assisted processing
更新于2025-09-23 15:21:01
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Laser-Induced Periodic Surface Structuring of Poly(trimethylene terephthalate) Films Containing Tungsten Disulfide Nanotubes
摘要： We report the study of the formation of Laser Induced Periodic Surface Structures (LIPSS), with UV femtosecond laser pulses (λ = 265 nm), in free-standing films of both Poly(trimethylene terephthalate) (PTT) and the composite PTT/tungsten disulfide inorganic nanotubes (PTT-WS2). We characterized the range of fluences and number of pulses necessary to induce LIPSS formation and measured the topography of the samples by Atomic Force Microscopy, the change in surface energy and contact angle using the sessile drop technique, and the modification in both Young’s modulus and adhesion force values with Peak Force-Quantitative Nanomechanical Mapping. LIPSS appeared parallel to the laser polarization with a period close to its wavelength in a narrow fluence and number of pulses regime, with PTT-WS2 needing slightly larger fluence than raw PTT due to its higher crystallinity and heat diffusion. Little change was found in the total surface energy of the samples, but there was a radical increase in the negative polar component (???). Besides, we measured small variations in the samples Young’s modulus after LIPSS formation whereas adhesion is reduced by a factor of four. This reduction, as well as the increase in ???, is a result of the modification of the surface chemistry, in particular a slight oxidation, during irradiation.
关键词： nanocomposites,ultrashort pulses,laser material processing,nanostructures,LIPSS
更新于2025-09-23 15:21:01
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Multispectral Management of the Photon Orbital Angular Momentum
摘要： We report on a programmable liquid crystal spatial light modulator enabling independent orbital angular momentum state control on multiple spectral channels. This is done by using electrically controllable “topological pixels" that independently behave as geometric phase micro-optical elements relying on self-engineered liquid crystal defects. These results open interesting opportunities in optical manipulation, sensing, imaging, and communications, as well as information processing. In particular, spectral vortex modulation allows considering singular spatiotemporal shaping of ultrashort pulses which may find applications in many areas such as material processing, spectroscopy, or elementary particles acceleration.
关键词： liquid crystal spatial light modulator,spectral vortex modulation,photon orbital angular momentum,geometric phase micro-optical elements,ultrashort pulses
更新于2025-09-23 15:21:01
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Investigation of ultrashort laser excitation of aluminum and tungsten by reflectivity measurements
摘要： We determine the laser-induced ablation threshold fluence in air of aluminum and tungsten excited by single near-infrared laser pulses with duration ranging from 15 to 100 fs. The ablation threshold fluence is shown to be constant for both metals, extending the corresponding scaling metrics to few-optical-cycle laser pulses. Meanwhile, the reflectivity is measured providing access to the deposited energy in the studied materials on a wide range of pulse durations and incident fluences below and above the ablation threshold. A simulation approach, based on the two-temperature model and the Drude–Lorentz model, is developed to describe the evolution of the transient thermodynamic and optical characteristics of the solids (lattice and electronic temperatures, reflectivity) following laser excitation. The confrontation between experimental results and simulations highlights the importance of considering a detailed description and evolution of the density of states in transition metals like tungsten.
关键词： Tungsten,Reflectivity,Femtosecond,Ablation,Metals,Ultrashort pulses
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE Colombian Conference on Communications and Computing (COLCOM) - Barranquilla, Colombia (2019.6.5-2019.6.7)] 2019 IEEE Colombian Conference on Communications and Computing (COLCOM) - Ultrashort Pulse Generation in EDFL Cavities using Graphene as Saturable Absorber for applications in optical communications systems
摘要： Graphene and 2D materials are being used in the design of light sources due to their wide absorption spectrum, ultrafast recovery time and high modulation depth. In this work, we present a experimental design of an modelocking Erbium-Doped-Fiber-Laser (EDFL) that uses graphene deposited onto D-shaped optical fiber, acting as a saturable absorber, in order to generate ultra-short pulses in an important region for optical communications: 1558.5 nm. To best of our knowledge, this is the first ultrashort pulses laser designed an experimentally validated in Colombia. The results shows a pulsed laser with a repetition rate of 33.3 MHz and a spectral width of 10 nm.
关键词： Saturable absorber,Graphene,Erbium-doped-fiber-laser,Mode-locking,D-shaped Optical fiber,Ultrashort pulses
更新于2025-09-16 10:30:52
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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) - Influence of the Doppler Effect on the Carrier-Envelope Phase
摘要： Carrier-envelope phase (CEP) stabilization plays an important role in the field of attosecond pulse generation and high-field physics [1]. Low-jitter CEP stabilization of ultrashort pulses typically relies on active stabilization schemes, either employing feedback or feed-forward control. However, both established methods come with a detrimental side effect. Feedback control directly modulates pump power or intracavity loss, which causes unwanted power fluctuations of the laser output. While feed-forward control does not corrupt the output stability, it nevertheless induces beam pointing variations in the acousto-optic frequency shifter employed. Here we demonstrate a novel method for modulating the CEP of a laser oscillator, which is based on the Doppler effect and displays neither of the above-mentioned side-effects.
关键词： Doppler effect,CEP stabilization,ultrashort pulses,carrier-envelope phase,laser oscillator
更新于2025-09-16 10:30:52
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Simulation of generation of ultrashort pulses in a laser based on the nonlinear polarisation evolution in two segments of a polarisation-maintaining fibre
摘要： A model describing generation of ultrashort optical pulses in a fibre cavity with Kerr nonlinearity and normal dispersion is constructed based on numerical solution of a nonlinear Schr?dinger equation. The model makes it possible to investigate the specific features of pulsed generation of a passively mode-locked laser based on the effect of nonlinear polarisation evolution (NPE) in two segments of a polarisation-maintaining (PM) fibre. It is shown theoretically that the proposed scheme may provide generation of linearly chirped optical pulses with a spectral width of above 25 nm and a centre wavelength of 1030 nm.
关键词： nonlinear Schr?dinger equation,fibre laser,ultrashort pulses,passive mode locking
更新于2025-09-16 10:30:52
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Modification of ABS wetting properties by ultrashort and short pulse lasers
摘要： Wetting is an important property of solid surfaces, where the surface roughness has a meaningful influence on it. This study focuses on the wetting behavior of micro-textures fabricated on acrylonitrile butadiene styrene (ABS) thermoplastic polymer to provide it anti-fingerprint properties. The structuring process was performed by ultrashort (picosecond) and short (nanosecond) pulses based on square pillars. Wetting behavior was assessed by water and oleic acid static and dynamic (hysteresis) contact angles. Both sort of micro-textures displayed a water contact angle tailored from 90. Apparent color changes induced by laser were assessed to get information about the aesthetical appearance.
关键词： ultrashort pulses,polymers,wettability,short pulses.,laser radiation,contact angle
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) - Common Pulse Retrieval Algorithm: A Fast and Universal Method to Retrieve Ultrashort Pulses
摘要： Measuring the temporal shape of ultrashort laser pulses is an important standard task in ultrafast optics. A multitude of methods has been devised for that purpose [1]. However, in many cases a specific, iterative algorithm has to be applied to retrieve the pulse shape from the measurement. In this work we present a common pulse retrieval algorithm (COPRA) that can be universally applied to such pulse measurement methods and compares favorably in terms of speed and accuracy to existing approaches [2]. For example, COPRA can be applied to the well-established frequency-resolved optical gating (FROG) [3], as well as, more recent techniques, such as dispersion scan (d-scan) [4] or time-domain ptychography (TDP) [5] (see Fig. 1). Generally, it is designed for a broad class of measurements where sets of pulse spectra after a nonlinear process such as second-harmonic generation (SHG) or third-harmonic generation (THG) are measured. Specifically, the measurement process has to be tunable by some parameter δ that forms the second measurement dimension. We call this class of measurements parametrized nonlinear process spectra (PNPS). COPRA now finds the pulse spectrum ?E(ω) that matches best to a PNPS measurement T meas(ω, δ ) in the least-squares sense. It does so in two stages: first the local iteration subsequently optimizes ?E(ω) with respect to single spectra, then the global iteration optimizes ?E(ω) with respect to the entire measurement. COPRA usually finds a least-squares solution to the pulse retrieval problem within a few hundreds iterations, i.e., within few tens of seconds on a standard workstation for usual measurement dimensions. This compares very favorably to existing approaches. Additionally, the retrieved pulses are more robust in the presence of Gaussian measurement noise than those retrieved by generalized projections or ptychography. Many existing pulse measurement schemes can directly benefit from COPRA for more robust and faster retrieval. Also, the framework of PNPS measurements may allow to gain more insight on fundamental questions of pulse measurement, will make measurement schemes more comparable and may lead to new and improved methods.
关键词： time-domain ptychography,pulse retrieval,frequency-resolved optical gating,dispersion scan,ultrashort pulses
更新于2025-09-12 10:27:22