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Item type:Publication, Access status: without files , Functionalization of sapphire surfaces using fs-laser radiation and selective etching(Laser Inst. of America, 2011-10); ; ; The change of surface properties, e.g. wettability and optical properties of sapphire surfaces, by direct writing of large ripple areas using a technique called "In-volume Selective Laser Etching" (ISLE) is demonstrated. In the process the sample is irradiated and by that modified/nano structured in the focal volume of the laser beam. The laser radiation is focused and scanned on the surface of the sample. Afterwards the sample is chemically wet etched using 48 % hydrofluoric acid (HF) to remove the modified material. In this paper the direct structuring of large ripple areas on transparent dielectrics up to 11 mm in diameter is shown for the first time. First achieved results will be discussed and an outlook to future applications will be given. The surface patterning is carried out with a 1.5 W FCPA laser system from IMRA.Publicationtype: Conference Paper15 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Waveguides and markings inside transparent materials by fs-laser radiation(Laser Inst. of America, 2011-10); ; ; Localized, three-dimensional refractive index changes are generated by focused femtosecond laser radiation (λ= 1045 nm, ≈ 500 fs) in the volume of transparent materials. Depending on the scanning direction and laser parameters both waveguides and colorful markings are produced in a depth of d = 150-200 μm below the surface of glass materials. The micro morphology of the irradiated structures is studied with light microscopy revealing a homogenous and crack-free modification. Depending on the angle of light incidence wavelengths of the visible light are diffracted at structured grids leading to bright colors in the observer's eyes. The optical guiding properties of the waveguides are investigated by far field measurements obtaining their numerical aperture. By using femtosecond double pulses instead of single pulses an increase in the numerical aperture of the fabricated waveguides is achieved. Results regarding the characteristics of double pulse waveguides in fused silica as well as examples for colorful marking in glass and crystals are presented.Publicationtype: Conference Paper11 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , 3D nano and micro structures in transparent materials by in-volume femtosecond laser processing(Laser Inst. of America, 2010-03); ; ; ; Nano as well as micro structuring in the volume of transparent materials is enabled by ultrafast laser radiation. By laser radiation with pulse durations in the fs and ps regime multi photon processes are efficiently induced resulting in a high resolution of less than 1 μm3, a very low heat input and a high writing flexibility in all three dimensions. High transparent materials such as sapphire and glasses are locally modified in the volume to change the refractive index for optical applications or to increase the corrodibility selectively for the manufacturing of micro channels and micro structured parts for the use in micro systems and medical technology. The miniaturization of products for micro optics, the medical technology and micro systems engineering requires transparent components with structure sizes in the micrometer range and accuracies of approx. 100 nm. In-volume Selective Laser-induced Etching (ISLE) is an appropriate manufacturing process for micro machining of transparent materials such as sapphire and glasses, e.g. fused silica. By focusing the laser radiation (wavelength 1040 nm, pulse duration 500 fs, repetition rate 0.1-5 MHz, pulse energy <1 μJ) in the volume the material is locally modified. By scanning the laser focus with pulse overlap inside the material, connected volumes of modified material are created. The modified volumes are subsequently removed by chemical etching in a second processing step using aqueous solution of e.g. HF or KOH. Periodical nano structures (ripples, nanoplanes) are fabricated inside transparent materials exploiting fs-laser induced nano optics with potential applications such as nano sieves for filtering, optical gratings or functionalized internal surfaces. Direct laser writing of waveguides in transparent materials by fs laser radiation is well known. Further applications include crack-free 3D micro markings in transparent materials consisting e.g. of micro-gratings, which result in a colorful experience in the observers eye due to diffraction and interference. To exploit the high manufacturing velocities possible with ultrafast lasers with repetition rates of several MHz a high speed scanning system with large numerical aperture and pre-compensation of spherical aberrations has been developed for in-volume nano and micro structuring. With this system high writing velocities (50-400 mm/s), small focus size (0.6-2.2 mm) and high precision (100-400 nm) are combined for the first time on rather large scanning fields (0.6-1.5 mm) and material depth of up to 2 mm.Publicationtype: Conference Paper14