José Luis Hernández-Pozos

The effect of NM-Au fabrication parameters by sputtering technique was investigated by modulating the current step (10 mA), the working pressure (0.15 mBar), the substrate-target distance (4.5 cm), the substrate type (FTO, Glass, Cellulose acetate and polystyrene) and the number of deposited layers at maximum times of 2 min. It was found that NM-Au has variable thicknesses, sizes and shapes (measured by TEM, profilometry, UV-Vis and conductivity), and that the shape and position of the plasmonic band changes due to the type of substrate for its different textures and refractive index. On the other hand, computational electromagnetics simulations (with the SCUFFEM program) were developed to study the magnitude of the NM-Au electric field and how this explains the plasmon effect on anthracene molecules measured by UV-Vis and TCSPC. Finally, a prototype sensor was designed based on some of the fabricated nanomaterials, detecting signals as a function of anthracene concentration.

In recent years, nanomaterials have become a source of solutions to effectively address various environmental, biological, pharmaceutical and food problems, often in novel ways, with high sensitivity and at low-cost. These materials have attracted a great deal of interest in the scientific community because they improve their properties, or unexpected effects arise compared to bulk materials. This article explores the concept of nanomaterials, their classification, some fabrication methods and the various applications of nanomaterials in miniaturized devices, whose purpose is to obtain systems that are easier to handle and transport due to their small size. The text does not pretend to be exhaustive but rather focuses on explaining to the reader the ins and outs of this fascinating world of nanomaterials and its newly emerging area of research known as nanotechnology.

We present a scheme, based on Bloch equations and Zeno-type measurements, that allows the control of the probability density evolution of the eigenstates of a V-type system. The equations are solved numerically and we present how the population in each level can be controlled using different sequences of “pulse measurements”. The entropy between the “measurement device” and the field used to perform the measurement process is evaluated for different strengths of such field, these calculations show that the entropy is maximized when we are in the Zeno regime. The results shown here unveil different possible strategies for controlling the population levels of a V-type system and could be implemented, for example, in trapped ions or RMN qubits.

The effect on the two‐photon absorption of heptamethine cyanines (HMCy) upon polymethinic chain substitution is explained via measurements with a femtosecond laser and time‐dependent/density functional theory calculations. An analysis of the optical properties of several HMCy is presented, emphasizing the similarities and differences between IR780 and HITC (used as a case study of HMCy), mainly by analyzing meso‐substitution and investigating the effect of intermediate structures between both molecules. The two‐photon absorption cross‐section of HITC diluted in methanol was measured, yielding a peak of 1838 GM at 830 nm. Spectroscopic and electronic structure computational data show that the change of polymethine chain substituents significantly affects excited state S ₄ of the molecules, modulating their transition moment and relative energy which, together with changes in the molecular geometry, govern non‐linear absorption.

We report the absorption/transmission properties of thin copper films slightly below the percolation limit produced by laser ablation; these samples show randomly positioned islands. Two types of films are grown: in the first type, copper is deposited on glass, and it is shown that as the amount of deposited copper approaches the percolation limit, the samples show enhanced light transmission; in the second set of samples, made of TiO$_2$/Cu/TiO$_2$ layers, the presence of titanium oxide inhibits light transmission enhancement, even though the same amount of copper has been deposited compared to the samples deposited on glass. We also present numerical calculations based on the discrete dipole method to simulate the optical behaviour of the copper films. The enhanced light transmission of the samples presented in this work resembles the Extraordinary Optical Transmission (EOT) observed in periodic metallic structures. The similarities and differences between experiment and numerical calculations and the possible use of these films as sensors are discussed.

In this work, the morphological changes induced by laser irradiation on silicon are investigated. The effects are analyzed under vacuum and oxygen atmospheres. The excitation source is an Nd:YAG laser at 1064 nm. A novel method to cause silicon microstructuring on large areas is presented. The analysis is done by scanning electron microscopy. When the microstructuring is performed in an oxygen atmosphere, the damage consists of a semi-ordered array of conical structures. The first stages of growth show the importance of the crystallographic orientation of the initial surface. In vacuum, the growth is irregular and random. In both cases, the microstucturing results in cones (oxygen) or bumps (vacuum) that protrude above the initial surface.