Ultrashort Laser Pulses Research Articles

Coupled Cluster Simulation of Impulsive Stimulated X-ray Raman Scattering.

Time-dependent equation-of-motion coupled cluster (TD-EOM-CC) is used to simulate impulsive stimulated X-ray Raman scattering (ISXRS) of ultrashort laser pulses by neon, carbon monoxide, pyrrole, and p-aminophenol. The TD-EOM-CC equations are expressed in the basis of field-free EOM-CC states, where the calculation of the core-excited states is simplified through the use of the core-valence separation (CVS) approximation. The transfer of electronic population from the ground state to the core- and valence-excited states is calculated for different numbers of included core- and valence-excited states, as well as for electric field pulses with different polarizations and carrier frequencies. The results indicate that Gaussian pulses can transfer significant electronic populations to the valence states through the Raman process. The sensitivity of this population transfer to the model parameters is analyzed. The time-dependent electronic density for p-aminophenol is also showcased, supporting the interpretation that ISXRS involves localized core excitations and can be used to rapidly generate valence wavepackets.

Coupling dynamics of dissipative localized structures: From polarized vector solitons to soliton molecules

Dissipative solitons are well known as representative nonlinear localized wave packets resulting from the composite balance of dispersion, nonlinearity, gain and loss in optical cavities. Since the last three decades, dissipative solitons keep as one of the most active research topics in the framework of nonlinear physics, not only for fundamental researches but also for various industrial applications. From one hand, due to the rich nonlinear dynamics, dissipative solitons have been considered as an ideal testbed to study the pumping-dissipation-bifurcation complexities. On the other hand, the emergences of dissipative solitons are tightly linked with the emission of ultrashort laser pulses, as well as the formation of broadband optical frequency combs. Compared with single-soliton counterpart, the multi-component dissipative solitons have exhibited even more fascinating properties and much wider range of applications, therefore the coupling dynamics of dissipative solitons is the blooming and emergent research area in the last decade. From this point of view, this review article covers the latest developments of compound dissipative solitons, not only in passive Kerr resonators, but also in mode-locked laser cavities. Ranging from polarized vector solitons to soliton molecules, the rising degree of freedom of these multi-component localized structures is boosting the discovery of novel nonlinear dynamics and underpin the various photonic applications in light science.

Excitonic Effect Drives Ultrafast Transition in Two-Dimensional Transition Metal Dichalcogenides.

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) are ideal platforms for exploring excitonic physics because of the tightly bound excitons. In this work, we observed the onset of band-edge exciton formation in monolayer MoS2 (WS2) and bilayer MoS2-WS2 by measuring the transient optical response upon excitation with ultrashort laser pulses. In addition to wavelength dependence on excitation under nonresonant excitation, we found that the onset of band-edge exciton formation in monolayer MoS2 (WS2) pumped in the exciton state is significantly faster than that with pumping in the nonexciton state, which could be attributed to the effective transition between exciton states induced by the excitonic effect. Besides, the onset of band-edge exciton formation in van der Waals heterostructures is similar to that for monolayer TMDCs regardless of charge transfer at the interface. Our work contributes to a better understanding of exciton dynamics in 2D TMDCs, providing a solid basis of the rational design of the 2D optoelectronic applications based on TMDCs.

Scaling up picosecond laser ablation of a LATGP-type glass-ceramic solid electrolyte for all-solid-state battery production

All-solid-state batteries are an intensively studied technology expected to complement conventional lithium-ion batteries in the near future. Research into fundamental production processes is crucial for enabling economic, industrial-scale all-solid-state battery production. Laser radiation is a production tool suited for contour cutting and surface structuring of inorganic solid electrolyte separators. In the scope of this work, the laser ablation of the commercial glass-ceramic solid electrolyte lithium aluminum germanium titanium phosphate (LAGTP) using ultrashort-pulsed laser radiation at different wavelengths, fluences, and pulse repetition rates is studied. Ablation thresholds, efficiencies, and rates were determined by manufacturing percussion drillings, trenches, and cavities. Geometry dependencies, such as the ablation rate decay with advancing depth during laser cutting, necessitated an application-oriented determination of ablation metrics. The surface qualities of the solid electrolyte layers were evaluated after laser ablation by scanning electron microscopy and surface roughness measurements. A wavelength of 532 nm was found to be beneficial compared to shorter and longer wavelengths in terms of productivity and ablation quality, reaching volume ablation efficiencies up to 36 μm3∙μJ−1 and surface roughnesses Sa below 500 nm. The determined metrics are discussed for ablation cutting and structuring of solid electrolyte layers in all-solid-state battery production, considering throughput and surface quality. The results provide insight into the ablation behavior of glass-ceramic materials and support the application of ultrashort-pulsed laser ablation in next-generation battery production.

Research on the control method of the structural stability of the precision tiled-grating

In a chirped pulse amplification device, tiled grating is a key component for compressing ultrashort pulse laser. The control system of the grating tiling device is essential for maintaining the stability of the array grating. In this study, a proportional-integral-derivative algorithm based on the latch compensation method and four-point center difference method is proposed for a truss-type 2 × 1 grating tiling device. Numerical analyses show that this method avoids the saturation loss in the stability control process of the array grating, effectively suppresses noise interference, and ensures the stability of the array grating. The prototype experiment shows that the use of this control algorithm can significantly improve the convergence speed and stability of the grating tiling device. Specifically, compared with a mechanism without a control algorithm, the time to reach the reference position for the first time is reduced by 39.1%, and the stability of the grating device is improved by 58.5%.

Independent multicolored bottle-beam generation using acousto-optic spatial shaping of a femtosecond laser beam.

We report on the development of a tunable spectral and spatial frequency shaping system for ultrashort laser pulses using acousto-optic filters. The system enables the creation of arbitrary axially symmetric multi-wavelength field configurations in the Ti:sapphire laser emission range near 800 nm and controlling them at a multi-kilohertz rate. We experimentally demonstrate independent generation of two-colored annular intensity distributions from a single femtosecond laser beam and a bottle beam having the hollow cylindrical volume with the aspect ratio of 9:1. This laser beam shaping system can be useful in creating advanced setups for an optical control of cold atoms.

Acousto-optic modulation of gigawatt-scale laser pulses in ambient air

Control over the intensity, shape, direction and phase of coherent light is essential in numerous fields, from gravitational wave astronomy, quantum metrology and ultrafast sciences to semiconductor fabrication. Modern photonics, however, can involve parameter regimes where the wavelength or high optical powers involved restrict control due to absorption, light-induced damage or optical nonlinearity in solid media. Here we propose to circumvent these constraints using gaseous media tailored by high-intensity ultrasound waves. We demonstrate an implementation of this approach by efficiently deflecting ultrashort laser pulses using ultrasound waves in ambient air, without the use of transmissive solid media. At optical peak powers of 20 GW, exceeding previous limits of solid-based acousto-optic modulation by about three orders of magnitude, we reach a deflection efficiency greater than 50% while preserving excellent beam quality. Our approach is not limited to laser pulse deflection; gas-phase photonic schemes controlled by sonic waves could potentially be useful for realizing a new class of optical elements such as lenses or waveguides, which are effectively invulnerable against damage and can operate in new spectral regions.

Laser Marker of the Latest Generation

Bromsgrove-based TLM Laser has introduced to the UK market the new Ultrashort pulse laser from FOBA Laser; plus, Macsa ID UK appoints new sales director as it looks to drive growth

Shock Compression of Molybdenum under Impact of Ultrashort Laser Pulses

Shock Compression of Molybdenum under Impact of Ultrashort Laser Pulses

High-NA Focusing of Ultrashort Laser Pulses in Bulk of ZnSe

High-NA Focusing of Ultrashort Laser Pulses in Bulk of ZnSe

Destruction of a magnesium alloy film in the condensed state by an ultrashort laser-driven shock wave

Laser-driven shock wave phenomena in a sub-micrometer Mg–4Al–2Zn alloy film are studied using spectral interferometry with spatial and temporal (1 ps) resolution. Upon irradiating the film through a glass substrate by 500 fs laser pulses, the ultrashort elastic compression pulses with the peak stress up to 4.6 GPa at a propagation distance of 0.5 μm were generated. Depending on the laser fluence, either spall fracture near the rear surface in the solid state or cavitation near the metal–glass interface in the liquid state was observed. The spall strength of the solid Mg alloy and the upper limit of the cavitation threshold in the melt at the strain rate of ∼109 s−1 were extracted from the free surface velocity history. The depth of fracture initiation was retrieved from the instant of the spall pulse exit, and the thickness of the molten layer was estimated to be 100–160 nm depending on laser fluence. The investigation of the residual morphology by scanning electron and atomic force microscopies revealed the presence of melting and nucleation within the irradiated area. The experimental findings are of interest for predicting the behavior of magnesium alloys in the condensed state at extremely high strain rates, for studying the physics of metastable states and for simulating the interaction of ultrashort laser pulses with thin film materials.

Switching the electrical properties of thin-film memristive elements based on GeTe by sequences of ultrashort laser pulses

Switching the electrical properties of thin-film memristive elements based on GeTe by sequences of ultrashort laser pulses

Automated endpointing in microelectronics failure analysis using laser induced breakdown spectroscopy

Failure analysis of microelectronics is essential to identify the root cause of a device's failure and prevent future failures. This process often requires removing material from the device sample to reach the region of interest, which can be done through various destructive methods, such as mechanical polishing, chemical etching, focused ion beam milling, and laser machining. Among these, laser machining offers a unique combination of speed, precision, and controllability to achieve a high-throughput, highly targeted material removal. In using lasers for processing of microelectronic samples, a much-desired capability is automated endpointing which is crucial for minimizing manual checks and improving the overall process throughput. In this paper, we propose to integrate laser-induced breakdown spectroscopy (LIBS), as a fast and high-precision material detection and process control means, into an ultrashort pulsed laser machining system, to enable vertical endpointing for sample preparation and failure analysis of microelectronics. The capabilities of the proposed system have been demonstrated through several sample processing examples.

Nonlinear propagation calculation-based irradiation process control for several mJ ultrashort pulse laser processing

In the realm of ultrashort pulse laser processing, surpassing the air ionization threshold, variations in focusing characteristics due to nonlinear optical phenomena pose challenges. Particularly, suitable irradiation conditions and position control methods for high pulse energy processing around 1 mJ remain unestablished. This study explores laser divergence phenomena in several mJ pulse energy range, examining both experimental and computational data. Quantitative demonstrations of laser focusing alterations, including divergence position and fluence, were achieved. Additionally, the dry laser peening effect was enhanced by energy-specific irradiation control. Numerical simulation-based visualization facilitates precise control, advancing the processing techniques.

Corrigendum to “A critical review on the simulation of ultra-short pulse laser interactions based on a two-temperature model (TTM)” [Opt. Laser Technol. 159 (2023) 109001

Corrigendum to “A critical review on the simulation of ultra-short pulse laser interactions based on a two-temperature model (TTM)” [Opt. Laser Technol. 159 (2023) 109001

Picosecond pulsed 532nm laser system for roughening and secondary electron yield reduction of inner surfaces of up to 15m long tubes.

Laser-induced surface structuring is a promising method to suppress electron mulitpacting in the vacuum pipes of particle accelerators. Electrons are scattered inside the rough surface structure, resulting in a low Secondary Electron Yield (SEY) of the material. However, laser processing of internal pipe surfaces with a large aspect ratio is technologically challenging in terms of laser beam guidance and focusing. We present a 532nm ultrashort-pulse laser setup to process the inner parts of 15m long beam vacuum tubes of the Large Hadron Collider (LHC). Picosecond pulses at a repetition rate of 200kHz are guided through an optical fiber toward an inchworm robot traveling inside the beam pipe. The system was installed, characterized, and tested for reliability. First surface treatments achieved the required scan precision. Cu2O-dominated nano-features were observed when processing at high average laser power (5 W) and slow scanning speed (5mms-1) in nitrogen flow, and the maximum SEY of copper was decreased from 2.1 to 0.7.

Generalizing amplitude swing modulation for versatile ultrashort pulse measurement.

In this work we broaden the amplitude modulation concept applied to the temporal characterization of ultrashort laser pulses with the amplitude swing technique. We theoretically study the effect of diverse types of relative amplitude and phase modulations. This variation of the replicas can be implemented by means of rotating zero-order waveplates to manipulate the delayed pulse replicas produced in a following multi-order waveplate, which can be more practical under certain conditions. We numerically simulate and study different scenarios under different modulations and for different noise levels and pulses. The proposed schemes are validated and compared through the experimental application to compressed and chirped pulses, confirming the applicability of the work. The simplicity, robustness and versatility of this ultrashort pulse measurement benefits the applications of ultrafast optics.

Coordination engineering in Nd3+-doped silica glass for improving repetition rate of 920-nm ultrashort-pulse fiber laser

Coordination engineering in Nd3+-doped silica glass for improving repetition rate of 920-nm ultrashort-pulse fiber laser

Fundamental Considerations and Analysis of the Energy Distribution in Laser Turning with Ultrashort Laser Pulses.

This article discusses the process of the laser turning of rotational symmetric, cylindrical components using ultrashort laser pulses with respect to the geometrical conditions and the resulting energy distribution during the laser turning process. As a result, process predictions and potential process optimizations are feasible. Particular attention is drawn to the laser spot formation on the cylindrical surface of the work piece in conjunction with the positioning of the laser beam relative to the rotation axis of the specimen. Based on fundamental calculations and experimental results, an optimum processing strategy is discussed, whereat the use of a trepanning optic in the laser turning process and the forming of a particular surface structure is additionally being issued.

Influence of Power and Frequency in the Femtosecond Laser Texturing of Ti6Al4V

Laser Surface Texturing (LST) has demonstrated to be the most reliable technique for the micro-modification of surfaces, allowing to obtain taylored surfaces. These modifications, depending on the basic micro-geometry and its repetition pattern, can provide special functionalities to a surface, such as hydrophilicity, hydrophobicity, reflectance, anti-bacterial, ostheo-integrability, as well as custom aesthetic, among others.Nevertheless, when a laser irradiates metallic surfaces, the micro-structure can be modified due to the heat induced, changing the mechanical properties of the surface. To avoid these effects, cold or ultra-short pulsed lasers must be used.A cold laser emits optical pulses with a duration below 1 ps (ultra-short pulses), in the domain of femtoseconds (fs=10-15 s). These ultra-short pulses, combined with high frequencies, in the megahertz region, leads to pulse trains with high repetition rates. This allows the sublimation of the material, keeping it relatively cold due to the short exposition time to irradiation.Ti6Al4V is the most used Ti alloy, thanks to its excellent weight/mechanical properties ratio. Nevertheless, its tribological behavior is very poor. Although there is intense research to improve it by using LST, the study of the influence of femtosecond laser parameters in the desired micro-geometries is still a gap in the scientific literature.In this research, a study of the influence of power (up to 50 W) and frequency (up to 2 MHz) in the fs-laser texturing of Ti6Al4V is presented. Local pulse repetition, linear and surface textures have been studied by combining power and frequency in these ranges, evaluating the geometry obtained by variable focus microscopy. The study carried out has allowed to determine the optimal set of parameters as a function on the target texture geometry, as well as the range in which the LST removal process changes from sublimation (for texturing) to melting (for micro-machining).