Dielectric Multilayer Thin Films Research Articles

Outdoor performance of a tandem InGaP/Si photovoltaic luminescent solar concentrator

We report the design, fabrication and outdoor characterization of a tandem luminescent solar concentrator/Si multi-junction photovoltaic module. Our tandem LSC/Si device consists of an InGaP LSC functioning as a top cell and a passivated contact Si bottom cell. The LSC comprises of an InGaP microcell array coupled to a polymer waveguide, loaded with CdSe/CdS core-shell quantum dot luminophores. The light trapping efficiency of the LSC waveguide is enhanced by encapsulation with photoluminescence trapping mirrors consisting of dielectric multilayer thin films. We demonstrate the performance of the LSC/Si device through a series of outdoor tests under various irradiance conditions conducted at the National Renewable Energy Laboratory. We report the first outdoor testing data of an LSC/Si tandem module, displaying maintained performance across varied diffusivity conditions for the LSC component. Finally, we model the tandem module performance using a ray optic simulation-based multiphysics model and forecast a pathway for high efficiency tandem LSC/Si module performance.

Characterization of Optical filters using Rutherford Backscattering Spectroscopy

The composition and thickness of optical filters, especially designed for the Auger project, were measured using the RBS method. The aim of this project is to detect the extensive air showers, developed by the interaction of very energetic cosmic rays with the atmospheric air. This swarm of particles, moving at the speed of light through the atmosphere, ionizes the nitrogen atoms, which radiate UV photons in the range of 300-420 nm. This nitrogen fluorescence is subsequently detected by fluorescence detectors having optical filters placed in front of their photomultipliers with high transmittance in the region of 300-420 nm and low transmittance outside this region, in order to maximize the photon signal to background photon ratio. The required transmittance of the optical filters led to specific production techniques, such as the dielectric multi-layer thin film deposition on a substrate, using high-low index UV-transparent materials. In order to select the optimal deposition technique for the mass production of these filters, the RBS method has been used, among others, to provide information concerning the thickness of the individual layers and possible deviations from the desired stoichiometry.The optical filters presented in this work were made of 6 and 12 thin film layers of WOzjMgFi deposited on UV glass. The samples were bombarded with α-particles at EQ — 3MeV, provided by the 5.5 MV Tandem Accelerator at NCSR "Demokritos". The RBS spectra were analyzed utilizing the computer simulation code RUMP.

Surface plasmons and Bloch surface waves: Towards optimized ultra-sensitive optical sensors

In photonics, the field concentration and enhancement have been major objectives for achieving size reduction and device integration. Plasmonics offers resonant field confinement and enhancement, but ultra-sharp optical resonances in all-dielectric multi-layer thin films are emerging as a powerful contestant. Thus, applications capitalizing upon stronger and sharper optical resonances and larger field enhancements could be faced with a choice for the superior platform. Here, we present a comparison between plasmonic and dielectric multi-layer thin films for their resonance merits. We show that the remarkable characteristics of the resonance behavior of optimized dielectric multi-layers can outweigh those of their metallic counterpart.

Refractive Index Sensor for Liquids and Solids Using Dielectric Multilayer Films Deposited on Optical Fiber End Surface

We propose and demonstrate a novel fiber-optic refractive index (RI) sensor using dielectric multilayer thin films (DMFs) deposited on an optical fiber end surface, which rejects the incident light with particular wavelength. We experimentally show that the center frequency of the reflected light spectrum changes in proportion to the RI of six kinds of liquids attached to the fiber end. Its coefficient of + 0.61 nm/RIU (refractive index unit) agrees well with our simulation results based on characteristic-matrix technique. We also show that this sensor is applicable to the RI measurement of solids.

UV protection filters by dielectric multilayer thin films on Glass BK-7 and Infrasil 301

The increasing use of Ultraviolet (UV) light in medicine, industrial environments, for cosmetic use, and even in consumer products necessitates that greater attention be paid to the potential hazards of this type of electromagnetic radiation. To avoid any adverse effects of exposure to this type of radiation, four suitable protection filters were produced to block three UV bands (UVA, UVB, and UVC). The design structure of the required dielectric multilayer filters was done by optical thin film technology using the absorbing property of UV radiation for the substrates and dielectric materials. The computer analyses of the multilayer filter formulas were prepared using Macleod Software for the production processes. The deposition technique was achieved on optical substrates (Glass BK-7 and Infrasil 301) by dielectric material combinations including Titanium dioxide (Ti 2O 3), Hafnium dioxide (HfO 2), and Lima (mixture of oxides SiO 2/Al 2O 3); deposition being achieved using an electron beam gun. The output results of the theoretical and experimental transmittance values for spectral band from 200 nm to 800 nm were discussed in four processes. To analyze the suitability for use in ‘real world’ applications, the test pieces were subjected to the durability tests (adhesion, abrasion resistance, and humidity) according to Military Standard MIL-C-675C and MIL-C-48497A.

Localized absorption effects during 351 nm, pulsed laser irradiation of dielectric multilayer thin films

A correlation is attempted between atomic-force-microscopy-mapped, postmortem damage morphologies in model thin films irradiated near threshold at 351 nm and finite-element, numerical simulations of the damage process in such multilayer films. This comparison permits deriving lower bounds on the temperature field at and near the absorbing defect, necessitating revisions to any damage model based solely on thermal conduction as the energy dissipation mechanism.

Application of thin-film optical filters to the temperature compensation of optical fiber grating-based devices

A major problem currently affecting the implementation of in-fiber refractive-index grating-based optical fiber devices is the drift in wavelength modulation due to the change in the ambient temperature. For accurate and reliable long-term operation of these devices, suitable temperature compensation techniques are a necessity. This paper presents a novel temperature compensation technique for in-fiber refractive index grating-based devices and components. The proposed technique is based on the temperature-dependent spectral characteristics of a dielectric multilayer thin-film interference filter fabricated on the endface of refractive-index grating impressed optical fiber. Temperature compensation is achieved by comparing the reflected intensities at the grating-reflected and the interference filter-reflected wavelengths. The proposed scheme also compensates for light source fluctuations and lead-in fiber bending losses.

Dielectric multilayer thin-film filters for WDM transmission systems

Dielectric multilayer thin-film (DMF) filters for a wavelength-division-multiplexing (WDM) system are discussed. It was found that a 23-layer 3-cavity bandpass-type DMF-filter made of TiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> is most suitable for this type of system. An optical multi/demultiplexer employing this type of bandpass DMF-filter is applicable to a two-way WDM transmission system.