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Ultrashort pulse laser processing of materials allows for precise machining with high accuracy. By increasing the repetition rate to several 100 kHz, laser machining becomes quick and cost-effective. Ultrafast laser processing at high repetition rates and peak intensities above 10^13 W/cm^2 can cause a potential hazard by generation of unwanted x-ray radiation. Therefore, radiation protection must be considered. For 925 fs pulse duration at a center wavelength of 1030 nm, the x-ray emission in air at a repetition rate of 400 kHz was investigated up to a
peak intensity of 2.6 × 10^14 W/cm^2. Based on the presented measurements, the properties of potential shielding materials will be discussed. By extending our previous works, a scaling of the x-ray radiation emission to higher peak intensities up to 10^15 W/cm^2 is described, and emitted x-ray doses are predicted.
Laser-Induced Periodic Surface Structures (LIPSS, ripples) are a universal phenomenon and can be generated in a contactless, single-step process on almost any material upon irradiation of solids with intense laser radiation. Nowadays, processing rates of up to m^2/min are enabling new industrial applications in medicine, optics, tribology, biology, etc. Depending on the specific type of LIPSS, their structural sizes typically range from several micrometers down to less than 100 nanometers – far beyond the optical diffraction limit – while their orientations exhibit a clear correlation with the local polarization direction of the laser radiation. From a theoretical point of view, however, a controversial and vivid debate has emerged during the last two decades, whether LIPSS originate from electromagnetic effects (seeded already during the laser irradiation) – or whether they emerge from matter reorganization processes, i.e. distinctly after the laser irradiation. This presentation reviews the currently existent theories of LIPSS. A focus is laid on the historic development of the fundamental ideas, their corresponding mathematical descriptions and numerical implementations, along with a comparison and critical assessment of the different approaches.
During the past few years significantly increasing research activities in the field of laser-induced periodic surface structures (LIPSS, ripples) have been reported since the generation of LIPSS in a single-step process provides a simple way of surface nanostructuring towards a control of optical, mechanical or chemical surface properties. In this contribution the current research state in this field is reviewed. The formation of LIPSS upon irradiation of metals, semiconductors and dielectrics by multiple linearly polarized Ti:sapphire fs-laser pulses (30-150 fs) is studied experimentally and theoretically. Different types of LIPSS with periods even below 100 nm can be generated. Their dynamics and formation mechanisms are analyzed and identified in ultrafast optical experiments. Complementing theoretical calculations of the laser-induced carrier dynamics address transient changes of the optical properties of the irradiated materials and reveal the importance of surface plasmon polaritons in the early stage of LIPSS formation. Various applications of these nanostructures are outlined.
Laser-induced periodic surface structures (LIPSS) are a universal phenomenon and can be generated on almost any material by irradiation with linearly polarized radiation. This chapter reviews the current state in the field of LIPSS, which are formed in a “self-ordered” way and are often accompanying materials processing applications. LIPSS can be produced in a single-stage process and enable surface nanostructuring and, in turn, adaption of optical, mechanical, and chemical surface properties. Typically, they feature a structural size ranging from several micrometers down to less than 100 nm and show a clear correlation with the polarization direction of the light used for their generation. Various types of LIPSS are classified, relevant control parameters are identified, and their material-specific formation mechanisms are analyzed for different types of inorganic solids, i.e., metals, semiconductors, and dielectrics. Finally, technological applications featuring surface functionalization in the fields of optics, fluidics, medicine, and tribology are discussed.
Laser-induced periodic surface structures (LIPSS) are a universal phenomenon and can be generated on almost any material by irradiation with linearly polarized radiation. This chapter reviews the current state in the field of LIPSS, which are formed in a “self-ordered” way and are often accompanying materials processing applications. LIPSS can be produced in a single-stage process and enable surface nanostructuring and, in turn, adaption of optical, mechanical, and chemical surface properties. Typically, they feature a structural size ranging from several micrometers down to less than 100 nm and show a clear correlation with the polarization direction of the light used for their generation. Various types of LIPSS are classified, relevant control parameters are identified, and their material-specific formation mechanisms are analyzed for different types of inorganic solids, i.e., metals, semiconductors, and dielectrics. Finally, technological applications featuring surface functionalization in the fields of optics, fluidics, medicine, and tribology are discussed.
Laser-induced periodic surface structures (LIPSS) are a universal phenomenon and can be generated on almost any material by irradiation with linearly polarized radiation. This chapter reviews the current state in the field of LIPSS, which are formed in a “self-ordered” way and are often accompanying materials processing applications. LIPSS can be produced in a single-stage process and enable surface nanostructuring and, in turn, adaption of optical, mechanical, and chemical surface properties. Typically, they feature a structural size ranging from several micrometers down to less than 100 nm and show a clear correlation with the polarization direction of the light used for their generation. Various types of LIPSS are classified, relevant control parameters are identified, and their material-specific formation mechanisms are analyzed for different types of inorganic solids, i.e., metals, semiconductors, and dielectrics. Finally, technological applications featuring surface functionalization in the fields of optics, fluidics, medicine, and tribology are discussed.
The study of laser-fabricated periodic nanostructures is one of the leading topics of today’s photonics research. Such structures on the surface of metals, semiconductors, dielectrics, or polymers can generate new material properties with special functionalities. Depending on the specific material parameters and the morphology of the structures, new devices such as microlasers, optical nanoswitches, optical storage devices, sensors or antifraud features can be realized. Furthermore, laser-generated surface textures can be used to improve the tribological properties of surfaces in contact and in relative motion—to reduce friction losses or wear, to modify the wettability or the cell and biofilm growth properties of surfaces through bioinspired laser engineering, for emerging medical applications, or as decoration elements for the refinement of precious goods.
This Special Issue “Laser-Generated Periodic Nanostructures” focuses on the latest experimental and theoretical developments and practical applications of laser-generated periodic structures that can be generated in a “self-organized” way (laser-induced periodic surface structures, LIPSS, ripples) or via laser interference-based direct ablation (often referred to as direct laser interference patterning, DLIP). We aimed to attract both academic and industrial researchers in order to collate the current knowledge of nanomaterials and to present new ideas for future applications and new technologies. By 8 August 2021, 22 scientific articles have been published in the Special Issue, see www.mdpi.com/journal/nanomaterials/special_issues/laser-generated_periodic.