Abstract:Micromachining of 1 mm thick dielectric and metallic substrates was conducted using femtosecond pulse generated filaments in water. Several hundred microjoule energy pulses were focused within a water layer covering the samples. Within this water layer, non-linear self-action mechanisms transform the beam, which enables higher quality and throughput micromachining results compared to focusing in air. Evidence of beam transformation into multiple light filaments is presented along with theoretical modeling results. In addition, multiparametric optimization of the fabrication process was performed using statistical methods and certain acquired dependencies are further explained and tested using laser shadowgraphy. We demonstrate that this micromachining process exhibits complicated dynamics within the water layer, which are influenced by the chosen parameters.
In this report we present results of linear and nonlinear optical properties of colloidal material consisting of triangle silver nanoparticles in distilled water. The nonlinear optical properties of the material were investigated by a Z-scan technique using femtosecond laser pulses with tunable wavelength. Nanoparticle suspension showed distinct spectra with absorption lines, emerging due to the plasmonic properties of the silver nanoparticles. Surface plasmon resonance peak change over a wide range of wavelengths from 400 to almost 1100 nm was observed when the size of silver nanoparticles varied from 20 to 150 nm. In the samples different nonlinear effects such as saturable absorption, two photon absorption and self-focusing were observed when the femtosecond pulse intensity was changed from 1 up to 100 GW/cm 2 .
Ultrashort pulse lasers have been established as precise and universal tools for the micromachining of solid materials (cutting, texturing …). For these applications the quality of the cutting cross-section is important. The use of a Gaussian beam profile and linear polarization leads to tapered cutting sidewalls. It is possible to change the polarization orientation in order to machine a material for obtaining straight and vertical sidewalls. For this purpose a specific polarization converter was used. The transformation of the polarization distribution from linear to radial and azimuthal is done by a subwavelength, binary grating creating a π phase shift between the TE and TM transmitted waves. In this paper we report on investigations on the influence of laser polarization (radial, azimuthal, circular, linear) on the ablation characteristics of molybdenum and PZT using an Yb doped crystal laser (500 fs) and compare these results with previously published results.
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