In the laser treatment of a workpiece (9), e.g. for surface hardening, melting, alloying, cladding, welding or cutting, the adverse effect of reflectivity of the surface, when a pure, monochromatic laser (6) is used, is remedied by the simultaneous application of a relatively shorter wavelength beam (1). The two beams (1)(5) may be combined by a beam coupler (4) or may reach the workpiece (9) by separate optical paths (not shown). The shorter wavelength beam (1) improves the coupling efficiency of the higher- powered laser beam (5).

Laser Material Processing

Fine-structured aluminium products with controllable texture by selective laser melting of pre-alloyed AlSi10Mg powder

Driven by functionality and purity demand for applications of inorganic nanoparticle colloids in optics, biology, and energy, their surface chemistry has become a topic of intensive research interest. Consequently, ligand-free colloids are ideal reference materials for evaluating the effects of surface adsorbates from the initial state for application-oriented nanointegration purposes. After two decades of development, laser synthesis and processing of colloids (LSPC) has emerged as a convenient and scalable technique for the synthesis of ligand-free nanomaterials in sealed environments. In addition to the high-purity surface of LSPC-generated nanoparticles, other strengths of LSPC include its high throughput, convenience for preparing alloys or series of doped nanomaterials, and its continuous operation mode, suitable for downstream processing. Unscreened surface charge of LSPC-synthesized colloids is the key to achieving colloidal stability and high affinity to biomolecules as well as support materials,...

Laser Synthesis and Processing of Colloids: Fundamentals and Applications

Physics of shock waves and high-temperature hydrodynamic phenomena - Ya.B. Zeldovich and Yu.P. Raizer (translated from the Russian and then edited by Wallace D. Hayes and Ronald F. Probstein); Dover Publications, New York, 2002, 944 pp., $34.

Laser beam machining (LBM) is one of the most widely used thermal energy based non-contact type advance machining process which can be applied for almost whole range of materials. Laser beam is focussed for melting and vaporizing the unwanted material from the parent material. It is suitable for geometrically complex profile cutting and making miniature holes in sheetmetal. Among various type of lasers used for machining in industries, CO2 and Nd:YAG lasers are most established. In recent years, researchers have explored a number of ways to improve the LBM process performance by analysing the different factors that affect the quality characteristics. The experimental and theoretical studies show that process performance can be improved considerably by proper selection of laser parameters, material parameters and operating parameters. This paper reviews the research work carried out so far in the area of LBM of different materials and shapes. It reports about the experimental and theoretical studies of LBM to improve the process performance. Several modelling and optimization techniques for the determination of optimum laser beam cutting condition have been critically examined. The last part of this paper discusses the LBM developments and outlines the trend for future research.

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Laser beam machining—A review

A brief review is given regarding ultrafast laser micromachining of materials. Some general experimental observations are first provided to show the characteristics of ultrafast laser micromachining. Apart from empirical research, mathematical models also appear to allow for a further and systematic understanding of these phenomena. A few fundamental ultrafast laser micromachining mechanisms are addressed in an attempt to highlight the physics behind the experimental observations and the mathematical models. It is supposed that a vivid view of ultrafast laser micromachining has been presented by linking experimental observations, mathematical models and the behind physics.

A review of ultrafast laser materials micromachining

Laser forming is fast emerging as a viable means for the shaping of metallic components, as a means of rapid prototyping and of adjusting and aligning. Relevant industry sectors include aerospace, automotive, and microelectronics. In contrast with conventional forming techniques this method requires no mechanical contact and hence offers many of the advantages of process flexibility associated with other laser manufacturing techniques such as laser cutting and marking. This article reviews the mechanisms involved and the main models proposed in laser forming and presents an overview of the main applications currently developed. An assessment is made of the potential for future development of this new technology.

Advances in laser forming

Laser surface treatment techniques, including laser surface melting (LSM) and laser surface alloying (LSA), have been the subject of considerable interest as a means of enhancing the corrosion performance of aluminium and its alloys. Microstructural modification together with the incorporation of non-equilibrium concentrations of alloying elements resulting from relatively rapid rates of cooling compared with conventional surface treatment techniques provide the basis for property enhancement. This paper considers microstructural evolution in a range of laser surface treated aluminium alloys including LSM of Al–Cu, Al–Si, Al–Zn, Al–Fe and Al–transitional element alloy systems; LSA of Al–Ni, Al–Cr and Al–Mo. Where reported, corrosion and other property determination in these systems is discussed. It is shown that surface alloys with unique microstructural and compositional characteristics have been produced by these techniques and that in many cases promising improvements in hardness and critical pitting potential compared with conventional alloys have been reported.

Microstructure and corrosion properties of laser surface processed aluminium alloys: a review

In understanding of the hot spot phenomenon in single-molecule surface enhanced Raman scattering (SM-SERS), the electromagnetic field within the gaps of dimers (i.e., two particle systems) has attracted much interest as it provides significant field amplification over single isolated nanoparticles. In addition to the existing understanding of the dimer systems, we show in this paper that field enhancement within the gaps of a particle chain could maximize at a particle number N>2, due to the near-field coupled plasmon resonance of the chain. This particle number effect was theoretically observed for the gold (Au) nanoparticles chain but not for the silver (Ag) chain. We attribute the reason to the different behaviors of the dissipative damping of gold and silver in the visible wavelength range. The reported effect can be utilized to design effective gold substrate for SM-SERS applications.

The influences of particle number on hot spots in strongly coupled metal nanoparticles chain.

http://pcwww.liv.ac.uk/~kuang/Publications/Zheng%20Kuang's%20pulications_files/1st%20journal%20paper.pdf

Ken Watkins

Papers

A review of ultrafast laser materials micromachining

Advances in laser forming

Microstructure and corrosion properties of laser surface processed aluminium alloys: a review

The influences of particle number on hot spots in strongly coupled metal nanoparticles chain.

High throughput diffractive multi-beam femtosecond laser processing using a spatial light modulator