Visible luminescence from hydrogenated amorphous silicon modified by femtosecond laser radiation

Visible luminescence is observed from the composite of SiO2 with embedded silicon nanocrystallites produced by femtosecond laser irradiation of hydrogenated amorphous silicon (a-Si:H) film in air. The photoluminescence originates from the defect states at the interface between silicon crystallites and SiO2 matrix. The method could be used for fabrication of luminescent layers to increase energy conversion of a-Si:H solar cells

Femtosecond laser printed microoptics in hydrogenated amorphous silicon

Conventional optics (e.g. lenses or mirrors) manipulates the phase via optical path difference by controlling thickness or refractive index of material. Recently, a promising type of optics emerged which exploits geometric phase shift, when a lightwave is transformed by parameter other than optical path difference, e.g. polarization. Here, wavefront is modified by introducing spatially varying anisotropy and is a result of Panchatraman-Berry phase [1]. Theoretically any phase pattern can be achieved solely by means of geometric phase with efficiencies reaching 100% [2]. This allows continuous optical phase shifts and without phase resets, in stark contrast to conventional elements, wherein phase profiles are encoded as discrete optical path variations in refractive index or thickness, limiting performance. The geometric phase optics is a promising alternative for controlling and manipulating light, but it stumbles on the lack of adequate fabrication technology

Dataset for: Ultrafast laser-induced metasurfaces for geometric phase manipulations

Direct-write femtosecond laser nanostructuring of 300 nanometer thick a-Si:H films results in space-variant functional metasurfaces with form birefringence of up to ne-no=&ndash;0.5. Engineering the orientation of local optical axis allows implementing continuous phase profiles of nearly any optical element including arrays of polarization micro-converters and micro lenses, polarization gratings and computer generated holograms with continuous phase gradients of ~1 rad/&micro;m.</span

Geometric phase holograms imprinted by femtosecond laser nanostructuring

We demonstrate direct-write laser nanostructuring of semiconductor thin-films and transparent dielectrics resulting in space-variant anisotropic materials. The continuous phase profile of nearly any optical component can be achieved solely by the means of geometric phase

Femtosecond laser induced crystallization of hydrogenated amorphous silicon for photovoltaic applications

Femtosecond laser assisted crystallization is used to produce nanocrystalline silicon from hydrogenated amorphous silicon. Changes in structural, optical, electrical and photoelectric properties of laser modified amorphous silicon were investigated. Laser treated films were characterized using atomic force microscopy, Raman spectroscopy, constant photocurrent method and current measurements. Crystalline volume fraction as well as conductivity of laser irradiated films increased with the applied laser fluence, while hydrogen concentration in the films was found to decrease with the fluence. Spectral dependences of absorption coefficient, measured by constant photocurrent method, are discussed in terms of hydrogen out-effusion and additional defect state formation in silicon films during the laser treatment

Visible luminescence from hydrogenated amorphous silicon modified by femtosecond laser radiation

Visible luminescence is observed from the composite of SiO2 with embedded silicon nanocrystallites produced by femtosecond laser irradiation of hydrogenated amorphous silicon (a-Si:H) film in air. The photoluminescence originates from the defect states at the interface between silicon crystallites and SiO2 matrix. The method could be used for fabrication of luminescent layers to increase energy conversion of a-Si:H solar cells

Dataset for Laser Material Processing with Tightly Focused Cylindrical Vector Beams

We demonstrate the modification of bulk and thin film materials, including silica glass, crystalline silicon and amorphous silicon, by tightly focused cylindrical vector beams with azimuthal and radial polarizations. The evidence of the longitudinal field is revealed by second harmonic generation in z-cut lithium niobate crystal. Despite the reduced threshold, modification of silicon materials in the center of the single pulse focused beam is not observed due to the enhanced reflection of longitudinal component at the interface of high-index-contrast media, proving that the longitudinal component of the tightly focused radially polarized beam is inefficient for the flat surface modification. Enhanced interaction of the longitudinal light field with silicon nanopillar structures generated after the first-pulse irradiation demonstrates that the multi-pulse regime should be implemented.</span

Structural and electrophysical properties of femtosecond laser exposed hydrogenated amorphous silicon films

This paper studies the effect of femtosecond laser treatment in air of hydrogenated amorphous silicon thin films (a-Si:H) on their structural, electrical and photoelectric properties. The possibility of laser-induced crystallization of a-Si:H films with controlled crystalline volume fraction was shown. A sufficient increase of dark conductivity was observed for laser treated a-Si:H films which crystallinity exceeds 7%. Such increase was attributed to change in conductivity mechanism. However, spectral dependences of absorption coefficient did not show any qualitative changes with the laser fluence increase. It was found that spallation and oxidation of the film took place when laser fluence became reasonably high

Giant birefringence and dichroism induced by ultrafast laser pulses in hydrogenated amorphous silicon

A femto- and picosecond laser assisted periodic nanostructuring of hydrogenated amorphous silicon (α-Si:H) is demonstrated. The grating structure with the subwavelength modulation of refractive index shows form birefringence (Delta.n ~ -0.6) which is two orders of magnitude higher than commonly observed in uniaxial crystals and femtosecond laser nanostructured silica glass. The laser-induced giant birefringence and dichroism in α-Si:H film introduce extra dimensions to the polarization sensitive laser writing with applications that include data storage, security marking, and flat optics