Waveplates modify polarization by generating a phase change. Laser Induced Periodic Surface Structures (LIPSS) have recently started to be studied as waveplates due to the birefringence in-duced by the nanoripples, easily fabricated in a one-step process by laser, where LIPSS morphology is defined by the characteristics of the laser process parameters and the substrate material. The optical properties of these waveplates are defined by LIPSS parameters such as period, depth or width of the ripples. In this work we have deposited thin film coatings on stainless steel samples containing LIPSS for different coating thickness and composition. Results show that thin film coatings are a good candidate for the tunability of LIPSS birefringence since the coating modifies the induced polarization change and reflectivity of the sample depending on coating thickness and composition, as expected from numerical simulations.
ZnO thin film on alumina has been deposited by RF sputtering and processed by two dimensional direct laser interference patterning (DLIP) using a nanosecond laser (λ=355nm). The thermodynamic and structural properties have been investigated. <p> </p>
Morphological characterization has shown a line-pattern structure with small alterations depending on the fluence of the laser (85 mJ/cm<sup>2</sup> or 165 mJ/cm<sup>2</sup>). In order to understand these modifications, a simulation has been carried out to model the transient temperature during the DLIP to study the temperature reached by the ZnO surface for the different fluences. Moreover, a comparison with a non-interference energy distribution pulse is also simulated to corroborate the model. <p> </p>
For samples processed by DLIP, a thermal annealing effect has been noticed when temperatures at the surface are between 1000K and 1800K. Due to the slow cooling process, a possible recrystallization of the material similar to a thermal treatment is obtained. For temperatures close or higher than 1800K, the material starts to ablate.
Laser interference lithography (LIL) is concerned with the use of interference patterns generated from two or several
coherent beams of laser radiation for the structuring of materials. This paper presents the work on the processes based on
resists and direct writing with laser interference lithography. In the work, a four-beam laser interference system was used
as a submicrometer structuring tool in which a high-energy pulsed, frequency-tripled and TM polarized Nd:YAG laser (355 nm) with a coherent length of 3 m, energy power up to 320 mJ/cm<sup>2</sup>, pulse duration of 8 ns and 10 Hz repetition rate was used as a light source. The experimental results were achieved with 2-beam and 4-beam interference patterning. The processes can be used to define submicron surface relieves in large areas for use in the field of MEMS.
Multi-beam laser interference lithography (MB-LIL) is a rapid and cost-effective maskless optical lithography technique
to parallelly pattern periodic or quasi- periodic micro/nano-structured material over large areas more than square
centimetres. An interference pattern between two or more coherent laser beams is set up and recorded in a recording
material of substrate. This interference pattern consists of a periodic series of geometries representing intensity minima
and maxima. The patterns that can be formed depend on the number and configuration of laser beams. This review
introduces the development and application of MB-LIL system for fabrication of micro/nano-structured material. At first,
it surveys various types of MB-LIL methods by classifying different beam configurations. Then the paper shows some
application results for fabrication 2D/3D micro/nano structure arrays by means of interference patterns with multi-exposed
or directly ablation technique. The patterend micro/nano-structure arrays include crossed diffraction grating
array in photoresist, 3D pattern in polymetric photonic crystals, and magnetic nanoarrays in thin film. Finally, an
innovative four-beam LIL system is introduced, which is being developed within the EC-granted project DELILA.
This paper presents a theoretical analysis of formation of 4-beam laser interference patterns for nanolithography.
Parameters of 4-beam interference patterns including the pattern amplitude, period, orientation and uniformity were
discussed. Analytical expressions were obtained for the spatial distribution of radiation of the interfering beams as a
function of their amplitudes, phases, angles of incidence on the sample, and polarization planes with computer
simulation and experimental results.
Nanoscale periodic and quasiperiodic relieves on fused quartz are of interest for the creation of a variety of optical and
electronic devices such as phase masks, one- and two-dimensional stamps for nanoimprint and wide-band antireflection
structures. The authors of this paper have developed a method of interference lithography to pattern nanoscale relief on
quartz with a high-power pulsed XeCl laser with high-quality output radiation at wavelength 308nm. One of the
advantages of the proposed technique is the significantly smaller influence of mechanical oscillations in an optical setup
on the results of nanoscale modification. The relief on quartz was formed with the use of a complete cycle of
lithography. As the mask, a two-layer structure of a copper film of 50nm in thickness and a photoresist of 400nm in
thickness were employed. The mask pattern was formed by exposure of a photoresist by two radiation beams of a XeCl
laser with energy density ~ 30mJ/cm<sup>2</sup>, aqueous-alkali development of a photoresist, and copper etching by the ion beam
(Ar<sup>+</sup>). Quartz was etched by the method of ion-beam reactive etching in a flow of CF<sub>4</sub> - O<sub>2</sub>(20%) gas mixture, with
etching rate 30nm/min.
The tailoring of the properties of silver nanoscale structures is of great interest to fields such as nanosensing and
biophotonics. Because of this, much effort is devoted to the development of new growth methods of silver
nanostructures. In this work, a fabrication process for two dimensional silver structures by infiltrating self-assembled
polystyrene spheres is presented. Additionally, the structural and optical characterizations of the fabricated structures are
We have experimentally observed the time evolution of the photoluminescence spectra of InGaN/GaN quantum wells with widths 3 and 4 nm in response to pulsed excitation at room temperature. We find that for both well widths the time evolution of the energy-integrated photoluminescence increases initially then decays and the spectrum displays a blue shift of the peak energy which then reverses. Through an iterative simulation of the carrier density, piezoelectric field and radiative recombination rate we calculate the behavior of these quantum well systems and find good agreement with the experimental data. The internal field present in the InGaN/GaN system is screened as carrier density increases, which combined with band filling and coulomb interactions result in a blue shift as the system is pumped and as recombination of the carriers occur a red shift is simulated. Although screening of the internal fields occurs our calculations show that at laser threshold there is still a large internal field present, 1.0 MVcm<sup>-1</sup>, which is 75 % of the unscreened value.