Multilevel phase Fresnel lenses (MPFLs) with a high numerical aperture for 0.58 THz frequencies were developed. The components based on a monocrystalline silicon wafer are prepared by patterning by a high-speed industrial-scale laser direct writing (LDW) system. Two consistent series of the terahertz-MPFLs with phase quantization levels varying between 2 and the continuous kinoform shape for the focal lengths of 5 and 10 mm were produced employing inherent flexibility of the LDW fabrication process. The focusing performance was studied at the optimal 0.58 THz frequency using a Gaussian beam profile and scanning 2D intensity distribution with a terahertz detector along the optical axis. The efficiency of the terahertz-MPFL was found to be dependent of the number of subzones. The position and orientation angles of the patterned plane of the silicon wafer were considered to reduce the effect of standing waves formation in the experiment.

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Laser interference ablation in silicon using femto-, pico-, and nanosecond pulses was investigated. The experimental and computational results provide information about nanoscale thermal diffusion during the ultra-short laser-matter interaction. The temperature modulation depth was introduced as a parameter for quality assessment of laser interference ablation. Based on the experiments and calculations, a new semi-empirical formula which combines the interference period with the laser pulse duration, the thermal modulation depth and the thermal diffusivity of the material was derived. This equation is in excellent agreement with the experimental and modelling results of laser interference ablation. This new formula can be used for selecting the appropriate pulse duration for periodical structuring with the required resolution and quality.

Fabrication of photonic devices requires fast and reliable microstructuring approach. For example, efficient generation of fine 2D patterns in thin metal films is needed in plasmonic metamaterial devices. In this paper, the authors present an approach for the flexible generation of the periodic pattern using a laser beam interference patterning setup. So far, interference patterning was mostly limited to the periodic patterns of lines and dots. A variety of interference patterns can be significantly increased by controlling the polarization orientation of each interfering beam. The authors demonstrate the experimental setup for polarization control in the confocal six-beam interference configuration. Various periodic intensity patterns were generated and observed with a CCD camera using this setup. Additionally, the generated patterns were replicated in a thin metal film experimentally. Efficient and simple fabrication process and relatively high patterning flexibility suggest that interference patterning with polarization control may become an important tool in metamaterial fabrication.