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.

We report on the high-voltage, noise, and radio frequency (RF) performances of aluminium gallium nitride/gallium nitride (AlGaN/GaN) on silicon carbide (SiC) devices without any GaN buffer. Such a GaN–SiC hybrid material was developed in order to improve thermal management and to reduce trapping effects. Fabricated Schottky barrier diodes (SBDs) demonstrated an ideality factor n at approximately 1.7 and breakdown voltages (fields) up to 780 V (approximately 0.8 MV/cm). Hall measurements revealed a thermally stable electron density at N_2DEG = 1 × 10¹³ cm⁻² of two-dimensional electron gas in the range of 77–300 K, with mobilities μ = 1.7 × 10³ cm²/V∙s and μ = 1.0 × 10⁴ cm²/V∙s at 300 K and 77 K, respectively. The maximum drain current and the transconductance were demonstrated to be as high as 0.5 A/mm and 150 mS/mm, respectively, for the transistors with gate length L_G = 5 μm. Low-frequency noise measurements demonstrated an effective trap density below 10¹⁹ cm⁻³ eV⁻¹. RF analysis revealed f_T and f_max values up to 1.3 GHz and 6.7 GHz, respectively, demonstrating figures of merit f_T × L_G up to 6.7 GHz × µm. These data further confirm the high potential of a GaN–SiC hybrid material for the development of thin high electron mobility transistors (HEMTs) and SBDs with improved thermal stability for high-frequency and high-power applications.

Numerical simulations and experimental characterization of laser-ablated focusing antireflective and phase-shifting structures for terahertz frequencies are presented. More than 10% shift of reflectance minimum to lower frequencies was predicted by simulations for relatively coarse structures with the period of 100 μm in comparison with that of a substantially smaller period and with results of the model used for the design of antireflective surfaces in the terahertz range. Such a shift of the resonance frequency can be employed to optimize the thickness of antireflective layers simultaneously obtaining additional means of more precise control of layer properties due to ablation of larger structures. Nearly 90% transmittance of silicon wafers within 0.5-0.6 THz frequencies was confirmed experimentally. Optical path differences equivalent to a half period at 0.53 THz, suitable for applications in high-efficiency zone plates, were demonstrated with high transmittance simultaneously. Possibilities of delay adjustment up to one wavelength were illustrated by numerical simulations. A focusing binary zone plate for 0.6 THz was produced employing phase-shift differences of the dual-function antireflective layer. Its close to diffraction-limited focusing performance was evaluated, further confirming sufficient uniformity of the structured layer.

In this research, the wetting property control of a stainless-steel surface, structured using parallel processing via an array of 64-femtosecond laser beams, is presented. The scanning of an 8 × 8-beam array over the sample was used to uniformly cover the large areas with LIPSS. The static water contact angle and the LIPSS period dependence on processing parameters were investigated. The wettability control of water droplets on laser-patterned stainless steel, ranging from contact angles of ~63°, similar to those of the plain surface, to the superhydrophobic surface with contact angles > 150°, was achieved. The relationship between the static water contact angle and the LIPSS parameters in the Fourier plane was investigated.

The hybrid multi-phase Fresnel lenses (H-MPFLs) were developed on silicon (Si) wafer at the selected frequency of 585 GHz. For this reason, the design of a standard MPFL was modified thoroughly in various outer zone areas in order to reduce complexity and manufacturing time of the diffractive optical elements (DOEs) by employing the direct laser ablation (DLA) processes. The phase offset was found by a precise control over the phase shift of incoming radiation in steps of π/12, revealing its optimal value to be of +π/4 independently on the hybridization order of the lens, the focusing gain of which was found to be up to 10 % higher than that achieved with a standard design MPFL. The numerical modeling data were confirmed by experiments demonstrating the effective THz beam focusing with H-MPFL samples to the diffraction limited spot size. Proposed development procedure can be further modified by scaling the hybrid lens design to other frequencies with different zone numbers and/or by employing other materials suitable for THz photonics integration on-chip with the semiconductor devices.