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Ultrafast laser processing of transparent non-crystalline solids Ultrafast laser processing of transparent non-crystalline solids employs non-linear absorption to induce structural changes within the target material interior without affecting its surface. This process has potential use in transmission welding of glasses, microfabrication of optical microdevices (waveguides) and three dimensional optical data storage. Altering the structure using a femtosecond laser in transparent materials occurs when the laser beam is tightly focused into the bulk of the sample. The laser intensity is concentrated within the focal volume and induces non-linear absorption of the deposited energy through multiphoton and avalanche ionization. Current research issues involve the study of the laser induced rearrangement of the ring structures of amorphous fused silica. Spatially resolved Raman spectroscopy and Rayleigh scattering are employed as non-destructive characterization techniques to show local densification and relative volume fraction changes of the ring structures within the affected region.
Femtosecond laser submicron texturing of multicrystalline silicon Femotsecond laser processing of surface of dielectric materials produce sub-micron size ripples which can be used for production of periodic structures. Texturing of silicon with sub-wavelength periodic structures can be used in production of solar cells for maximization of optical absorption. If textured structures are much smaller than optical wavelengths, light trapping is achieved via transition of the optical constants from the ambient atmosphere to the bulk Si instead conventional multiple reflections. Usage of femtosecond laser is advantageous because it can produce periodic structures independent from the crystal orientation which enables usage of multicrystalline silicon instead of single crystals which are more expensive.
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