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Reconstructing ultrafast energy-time-entangled two-photon pulses
摘要： The generation of ultrafast laser pulses and the reconstruction of their electric fields is essential for many applications in modern optics. Quantum optical fields can also be generated on ultrafast timescales; however, the tools and methods available for strong laser pulses are not appropriate for measuring the properties of weak, possibly entangled pulses. Here, we demonstrate a method to reconstruct the joint-spectral amplitude of a two-photon energy-time entangled state from joint measurements of the frequencies and arrival times of the photons, and the correlations between them. Our reconstruction method is based on a modified Gerchberg-Saxton algorithm. Such techniques are essential to measure and control the shape of ultrafast entangled photon pulses.
关键词： joint-spectral amplitude,quantum optical fields,energy-time entangled state,ultrafast laser pulses,Gerchberg-Saxton algorithm
更新于2025-09-23 15:19:57
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Sub-100 nm 2D nanopatterning on large scale by ultrafast laser energy regulation
摘要： Coupling ultrafast light to surface nanoreliefs leads to periodic patterns achieving record processing scales down to tens of nanometers. Driven by near-field interactions, the promising potential of the spontaneous pattern formation relies on the scale-up manufacturing one-step process. Here, we report the self-assembly of unconventional arrays of nanocavities of 20 nm diameter with a periodicity down to 60 nm upon ultrafast laser irradiation of a nickel surface. In stark contrast to laser-induced surface ripples, which are stochastic and suffer from a lack of regularity, the 2D patterns present an unprecedented uniformity on extreme scales. The onset of nanocavity arrays ordered in a honeycomb lattice is achieved by overcoming the anisotropic polarization response of the surface by a delayed action of cross-polarized laser pulses. The origin of this self-arrangement is identified as a manifestation of Marangoni convection instability in a nanoscale melt layer, destabilized by the laser-induced rarefaction wave.
关键词： nanopatterning,self-assembly,ultrafast laser,Marangoni convection,nanocavities
更新于2025-09-23 15:19:57
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Unidirectional transport and effective collection of underwater CO2 bubbles utilizing ultrafast-laser-ablated Janus foam
摘要： Manipulating gas bubbles in aqueous ambient is of great importance for applications in water treatment, gas collection and matter transport. Here, a kind of Janus foam is designed and fabricated by one-step ultrafast laser ablation of one side of cooper film, which is treated to be superhydrophobic. The Janus foam exhibits not only the capability of unidirectional transport of underwater bubbles, but also gas collection with favorable efficiency up to ~15 mL cm-2 min-1. The underlying physical mechanism is attributed to the cooperation of the buoyancy, adhesion and wetting gradient forces imposed on the bubbles. As a paradigm, the underwater chemical reaction between unidirectional CO2 gas flow and alkaline phenolphthalein solution is demonstrated via the Janus foam. This facile and low-cost fabrication approach for Janus foam will find broad potential applications for effective bubble transport, carbon capture and controllable chemical reactions in aqueous conditions.
关键词： Janus foam,Unidirectional bubble transport,Ultrafast laser,Wetting gradient force,Directional bubble collection
更新于2025-09-23 15:19:57
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Attosecond Streaking Time Delays: Finite-Range Interpretation and Applications
摘要： We review theoretical studies of the attosecond streaking time delay concept in photoionization via the investigation of the electron dynamics in the streaking field after the transition of the photoelectron into the continuum upon absorption of an extreme ultraviolet photon. Based on the results, a so-called finite range interpretation was introduced, which highlighted that the delay is accumulated until the streaking pulse ends and, hence, over a finite range of the potential of the parent ion. Following a discussion of the analysis leading to this interpretation, we summarize a few applications which provide insights into different aspects of the streaking time delay concept in photoionization. Besides a review of previously presented results, we give an analysis of the relevance of the first half-cycle of the streaking field and an outlook regarding the perspective of using the streaking method to resolve dynamical changes in the potential that the photoelectron explores during its propagation in the continuum.
关键词： attosecond measurement techniques,streaking time delays,photoionization,ultrafast laser science
更新于2025-09-19 17:15:36
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Three-Dimensional Laser Printing of Macro-Scale Glass Objects at a Micro-Scale Resolution
摘要： Three-dimensional (3D) printing has allowed for the production of geometrically complex 3D objects with extreme flexibility, which is currently undergoing rapid expansion in terms of materials, functionalities, as well as areas of application. When attempting to print 3D microstructures in glass, femtosecond laser-induced chemical etching (FLICE)—which is a subtractive 3D printing technique—has proved itself a powerful approach. Here, we demonstrate the fabrication of macro-scale 3D glass objects of large heights up to ~3.8 cm with an identical lateral and longitudinal feature size of ~20 μm. The remarkable accomplishment is achieved by revealing an unexplored regime in the interaction of ultrafast laser pulses with fused silica, which results in depth-insensitive focusing of the laser pulses inside fused silica.
关键词： light-field manipulation,ultrafast laser microfabrication,3D glass printing
更新于2025-09-19 17:13:59
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Hierarchical Laser-Patterned Silver/Graphene Oxide Hybrid SERS Sensor for Explosive Detection
摘要： We demonstrate an ultrafast laser-ablated hierarchically patterned silver nanoparticle/graphene oxide (AgNP/GO) hybrid surface-enhanced Raman scattering (SERS) substrate for highly sensitive and reproducible detection of an explosive marker 2,4-dinitrotoluene (2,4-DNT). A hierarchical laser-patterned silver sheet (Ag?S) is achieved by ultrafast laser ablation in air with pulse energies of 25, 50, and 100 μJ. Multiple laser pulses at a wavelength of 800 nm and a pulse repetition rate of 50 fs at 1 kHz are directly focused on Ag?S to produce and deposit AgNPs onto Ag?S. The surface morphology of ablated Ag?S was evaluated using atomic force microscopy, optical pro?lometry, and ?eld emission scanning electron microscopy (FESEM). A rapid increase in the ablation rate with increasing laser energy was observed. Selected area Raman mapping is performed to understand the intensity and size distribution of AgNPs on Ag?S. Further, GO was spin-coated onto the AgNPs produced by ultrafast ablation on Ag?S. The hierarchical laser-patterned AgNP/GO hybrid structure was characterized using FESEM, high-resolution transmission electron microscopy, X-ray di?raction, Fourier transform infrared spectroscopy, and Raman spectroscopy. Further, hierarchical laser-patterned AgNP/GO hybrid structures have been utilized as SERS-active substrates for the selective detection of 2,4-DNT, an explosive marker. The developed SERS-active sensor shows good stability and high sensitivity up to picomolar (pM) concentration range with a Raman intensity enhancement of ～1010 for 2,4-DNT. The realized enhancement of SERS intensity is due to the cumulative e?ect of GO coated on Ag?S as a proactive layer and AgNPs produced by ultrafast ablation.
关键词： silver nanoparticle/graphene oxide (AgNP/GO) hybrid,ultrafast laser ablation,explosive detection,surface-enhanced Raman scattering (SERS),2,4-dinitrotoluene (2,4-DNT)
更新于2025-09-19 17:13:59
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Experimental study on two-phase boiling in wavy copper microchannels fabricated with ultrafast laser micromachining
摘要： In this study, the sinusoidal wavy (SW) copper microchannels with triangular cross section were fabricated with the ultrafast laser micromachining approach. The flow boiling of de-ionized water in SW microchannel were experimentally studied under mass fluxes of 43.43-217.15 kg/(m2s) and heat fluxes of 0-590 kW/m2. The flow patterns in the SW microchannels were visually observed and the boiling heat transfer characteristics were analyzed based on the obtained data. It shows the SW microchannel has a maximum enhancement of 127.7% in local heat transfer coefficient with an acceptable increase of pressure loss compared to the straight one in present work. In SW microchannel, a low degree of superheat can trigger the onset of nucleate boiling. A slow decreasing tendency of local heat transfer coefficient under a high effective heat flux or a high vapor quality was observed. The heat transfer mechanism of flow boiling in SW microchannel was analyzed based on the experimental visualization. Nucleate boiling and thin film evaporation are the dominant modes under different thermal boundary conditions. The flow boiling instability phenomenon in microchannels can be diminished using the wavy structures.
关键词： Boiling heat transfer,Sinusoidal wavy microchannel,Flow instability,Ultrafast laser micromachining
更新于2025-09-19 17:13:59
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Femtosecond lasers for high-precision orthopedic surgery
摘要： Laser micromachining with ultrashort pulses has shown great promise for clean, safe surgical treatment of bone tissue. However, comparisons of performance and development of “best practice” have been hampered by the difficulty of comparing results across a wide variety of experimental approaches and under surgically irrelevant conditions (e.g., dried, dead bone). Using a femtosecond (fs) pulsed laser system (τ = 140 fs, repetition rate = 1 kHz, λ = 800 nm), a comprehensive study of femtosecond laser microsurgery using the standard metrics of laser micromachining (ablation threshold, incubation effects, ablation rates, effect of focal point depth within the material and heat affected zone (HAZ)) was conducted on live, freshly harvested bovine and ovine cortical bone. Three important points of optimism for future implementation in the surgical theatre were identified: (1) the removal of material is relatively insensitive to the focal point depth within the material, removing the need for extreme depth precision for excellent performance; (2) femtosecond laser ablation of fresh bone demonstrates very little incubation effect, such that multiple passes of the laser over the same region of bone removes the same amount of material; and (3) the complete absence of collateral damage, heat- or shock-induced, on both the macro- and microscopic scales can be achieved readily, within a broad parameter range. Taken together, these results indicate a handheld or robotic deployed fiber laser platform for femtosecond laser microsurgery is a very viable prospect.
关键词： Laser ablation,Ultrafast laser micromachining,Femtosecond microsurgery,Laser micromachining,Orthopedic surgery
更新于2025-09-16 10:30:52
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Accelerator for Ultrafast Laser Serial Production
摘要： The world of serial applications has long been denied the possibility of ablation processes with ultrafast pulsed laser radiation due to high investment costs and low ablation rates. Nowadays, process scaling with advanced beam shaping technologies make use of the available high laser powers and therefore opens up possibilities for serial processing of individual components. But the exclusive focus on the main time of laser processing is not enough for a production system. Only the combined operation of handling systems, measurement technology, and process automation allow the ultrafast laser technology to spread further into volume markets.
关键词： Production Data Acquisition,Process Automation,Ultrafast Laser Machining,Beam Shaping,Condition Monitoring
更新于2025-09-16 10:30:52
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[Laser Institute of America ICALEO? 2016: 35th International Congress on Applications of Lasers & Electro-Optics - San Diego, California, USA (October 16–20, 2016)] International Congress on Applications of Lasers & Electro-Optics - Ultrafast laser trepanning process and modeling
摘要： We present an engineering model of ultrafast laser ablation with normal or non-normal (oblique) laser beams. It can be applied to trepanning drilling but also to zero-taper cutting. Specific experiments on line ablation are presented to understand how oblique beams can control the walls conicity. Industrial strategies for processing with high throughput and high quality are considered.
关键词： ultrafast laser,industrial processing,oblique beams,ablation,zero-taper cutting,trepanning drilling
更新于2025-09-16 10:30:52