High Refractive Layer Research Articles

Modification of the interaction of an electron with its own radiation field in photonic crystals with high-refractive layers

The self-energy interaction of atoms placed in air voids of one-dimensional photonic crystals with high-refractive layers is considered. Modification of the interaction of an electron with its own radiation field in the photonic crystal medium gives rise to a correction to its mass and kinetic energy. We demonstrate the photonic density of states of the periodic structure and the dependence of the mass correction of the valence electron of hydrogen atom and the alkali metals on the refractive index of the one-dimensional photonic crystal based on alternating amorphous hydrogenated layers of silicon nitride a-SiN x : H and vacuum, and layers of the high refractive index metamaterial consisting of Au nanoparticles with a dielectric matrix based on HfO2 and vacuum. The tunability of these materials gives rise to the tunability of the mass correction over a wide range. It is shown that the effect under study leads to significant shifts in the energy levels of atoms which is important for controlling physical and chemical processes, creating new linear light sources, and He-Ne-like lasers.

Mid-infrared Fe2+:ZnSe semiconductor saturable absorber mirror for passively Q-switched Er3+-doped ZBLAN fiber laser

A mid-infrared (mid-IR) semiconductor saturable absorber mirror (SESAM) based on Fe2+:ZnSe for passively Q-switched Er3+-doped ZBLAN fiber laser has been demonstrated. Fe2+:ZnSe SESAM was fabricated by electron beam evaporation method. Fe2+ was innovatively doped into the reflective Bragg stack, in which ZnSe layer served as both doped matrix and high refractive layer during the fabricating process. By using the Fe2+:ZnSe SESAM, stable passively Q-switched pulses with the minimum pulse width of 0.43 μs under a repetition rate of 160.82 kHz were obtained. The recorded maximum average output power of 873 mW with a peak power of 12.59 W and pulse energy of 5.43 μJ were achieved. The results demonstrated a new method for fabricating Fe2+:ZnSe SESAM, which can be used in compact mid-IR Q-switched fiber laser.

Anti-reflection coatings with enhanced abrasion and scratch resistance properties

The development of multifunctional coatings plays a crucial role in the achievement of more competitive glasses for optical and solar application, among others. In this respect, coatings that provide high transmittance together with abrasion resistance could mean an added value to such glasses. Herein, we report design and preparation of novel multifunctional coatings that present anti-reflection (AR), scratch and abrasion resistance properties. This is achieved by a coating structure with a composite top layer comprising at least one type of metal oxide (ZrO2 or TiO2) or silane compound with low-refractive-index SiO2 layer. The above composite layer is applied onto a high refractive metal oxide layer, either titania or zirconia. The properties of the coatings were studied by different characterization techniques such as UV–visible–NIR spectrophotometer, FESEM, FIB, SEM–EDAX, haze and transmission meter, ellipsometer, pencil hardness tester, Taber Abrader and water contact angle measurement. The results indicate that the AR films produced by a bilayer system especially using a low refractive nanocomposite layer as a top layer and a high refractive layer as a bottom layer showed a high transmission in the visible range with comparatively better abrasion and scratch resistances. Moreover, the coatings developed on silicon wafer used as an absorber substrate for PV application exhibited an excellent low reflectance property, <2.5 % average reflection from 300 to 1500 nm which makes it applicable in both optical and photovoltaic systems with high mechanical stability. Composite bilayer anti-reflection coatings with enhanced abrasion and scratch resistance properties.

The Influence of a Power Law Distribution of Cluster Size on the Light Transmission of Disordered 1-D Photonic Structures

A better understanding of the optical properties of random photonic structures is beneficial for many applications, such as random lasing, optical imaging and photovoltaics. Here we investigated the light transmission properties of disordered photonic structures in which the high refractive index layers are aggregated in clusters. We sorted the size of the clusters from a power law distribution tuning the exponent a of the distribution function. The sorted high refractive layer clusters are randomly distributed within the low refractive index layers. We studied the total light transmission, within the photonic band gap of the corresponding periodic crystal, as a function of the exponent in the distribution. We observed that, for a within the interval [0,3.5], the trend can be fitted with a sigmoidal function.

One dimensional disordered photonic structures characterized by uniform distributions of clusters

We investigated one dimensional disordered photonic structures by grouping high refractive index layers in clusters, randomly distributed within layers of low refractive index. We control the maximum size of the high refractive layer clusters and the ratio of the high–low refractive index layers, which we call the dilution of the system. By studying the total transmission of the disordered structure within the photonic band gap of the ordered structure as a function of the maximum cluster size, we observe a dip of the total transmission for a specific maximum cluster size. This value increases with increasing dilution. Moreover, within one dilution we observe oscillations of the total transmission with increasing cluster size.

Titanate Nanosheets as High Refractive Layer in Vertical Microcavity Incorporating Semiconductor Quantum Dots

The use of titanium dioxide as the high refractive index component in optical structures is very attractive because of its optical properties. In this work, we developed a novel synthesis of colloidal layered titanate consisting of nanosheets of titanium oxide. A colloidal solution of titanate nanosheets was deposited by spin coating and treated by thermal annealing and UV irradiation, obtaining high refractive index thin films. Transmission electron microscopy, X-ray diffraction, and spectroscopic ellipsometry were used to characterize titanate powders and the evolution of titanate films under the employed treatments. The developed low temperature UV-assisted titanate processing was found to be suitable in the fabrication of multilayer dielectric Bragg mirrors, which can be used in a vertical optical microcavity incorporating CdSe@ZnS quantum dots (QDs) in the defect layer. The developed fabrication procedure did not result in the loss of QDs emission properties, allowing for optical characterization of ...

Structure and properties of titanium oxide layers deposited by reactive plasma activated electron beam evaporation

Titanium oxide layers were deposited by reactive electron beam evaporation with and without additional plasma activation by spotless arc discharge. The influence of substrate temperature and plasma activation on structure and properties of TiO2 layers are presented. The layers were deposited with very high deposition rates between 40 and 70 nm/s.XRD investigations have revealed that structure of all layers deposited at substrate temperature (TS) below 150 °C is amorphous. Without plasma activation and at substrate temperature above 200 °C layers with anatase phase were deposited. On the other hand with plasma activation the degree of substrate ion bombardment controls the formation of anatase or rutile phase.Furthermore a drastic influence of plasma activation on the properties of the layers could be found. Without plasma activation the refractive index at 550 nm only amounts to between 2.02 and 2.29 depending on substrate temperature. With plasma activation a drastic raise of refractive indexes to values between 2.30 and 2.58 can be reached. In addition the hardness of the layer is obviously influenced by plasma activation. At TS below 150 °C hardness is raised from 2.0 to 6.7 GPa. The formation of the rutile phase in layers deposited with plasma activation is linked with a further increase of hardness up to 12 GPa.Measurements of the contact angle show a promising super hydrophilicity of anatase layers. Therefore these layers should be well-suited as coatings with self-cleaning or antifogging properties. At TS below 150 °C the plasma activation enables the deposition of dense, high-refractive layers at very high deposition rates for applications as optical layers.

Growth Conditions, Optical and Dielectric Properties of Yttrium Oxide Thin Films

Thin Y2O3 films are grown by reactive synthesis, their optical and dielectric properties (electric resistivity, dielectric losses and permittivity, electric strength, and refractive index) are measured. Their dependence upon deposition parameters (deposition rate and reactive gas pressure) is investigated. Comparison of experimental data with those obtained by film growth modelling by the Monte-Carlo method suggests an insignificant influence of diffusion jumps and long-range order on the formation of Y2O3 films at low deposition temperature (300 to 400 K). The perspectives of Y2O3 films as dielectric layers in integrated circuits and high refractive layers for laser mirrors are shown.