Optical Properties of Nanocomposite Thin-Films

2006 ◽  
Author(s):  
Anna Garahan ◽  
Laurent Pilon ◽  
Juan Yin ◽  
Indu Saxena
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Maxwell’S Equations ◽  
Maxwell's Equations ◽  
Volume Fraction ◽  
Effective Index ◽  
Absorption Index ◽  
Index Of Refraction ◽  
Nanocomposite Thin Films ◽  
Effective Index Of Refraction

This paper aims at developing numerically validated models for predicting the through-plane effective index of refraction and absorption index of nanocomposite thin-films. First, models for the effective optical properties are derived from previously reported analysis applying the volume averaging theory (VAT) to the Maxwell's equations. The transmittance and reflectance of nanoporous thin-films are computed by solving the Maxwell's equations and the associated boundary conditions at all interfaces using finite element methods. The effective optical properties of the films are retrieved by minimizing the root mean square of the relative errors between the computed and theoretical transmittance and reflectance. Nanoporous thin-films made of SiO2 and TiO2 consisting of cylindrical nanopores and nanowires are investigated for different diameters and various porosities. Similarly, electromagnetic wave transport through dielectric medium with embedded metallic nanowires are simulated. Numerical results are compared with predictions from widely used effective property models including (1) Maxwell-Garnett Theory, (2) Bruggeman effective medium approximation, (3) parallel, (4) series, (5) Lorentz-Lorenz, and (6) VAT models. Very good agreement is found with the VAT model for both the effective index of refraction and absorption index. Finally, the effect of volume fraction on the effective complex index of refraction predicted by the VAT model is discussed. For certain values of wavelengths and volume fractions, the effective index of refraction or absorption index of the composite material can be smaller than that of both the continuous and dispersed phases. These results indicate guidelines for designing nanocomposite optical materials.

Effective Optical Properties of Nanoporous Silicon

2005 ◽  
Author(s):  
Matt Braun ◽  
Laurent Pilon
Keyword(s):  
Optical Properties ◽  
Maxwell’S Equations ◽  
Maxwell's Equations ◽  
Volume Averaging ◽  
Incident Radiation ◽  
Absorption Index ◽  
Numerical Results ◽  
Index Of Refraction ◽  
Solid Matrix ◽  
Nanoporous Silicon

Nanoporous materials consist of nanosize voids embedded in a solid matrix. The pores can be closed or open and have various shapes and sizes. Their applications range from optical and optoelectronics devices to biosensors. In order to effectively utilize and characterize nanoporous media for these various applications, models that describe their effective optical properties are necessary. Numerous effective medium models have been proposed. However, validations of these models against experimental data are often contradictory and inconclusive. This issue was numerically investigated by solving the two-dimensional Maxwell’s equations in absorbing nanoporous silicon thin-films. All interfaces are assumed to be optically smooth and characteristic pore size is much smaller than the wavelength of incident radiation so electromagnetic wave scattering by pores can be safely neglected. The envelope method was then used to retrieve the effective index of refraction and absorption index from the computed transmittance. The numerical results agree very well for both the index of refraction and the absorption index with a recent model obtained by applying the Volume Averaging Theory (VAT) to the Maxwell’s equations. However, commonly used models such as the Maxwell-Garnett, Bruggeman, parallel, and series models systematically and sometimes significantly underpredict the numerical results.

scholarly journals NEGATIVE REFRACTION AND SUBWAVELENGTH FOCUSING USING PHOTONIC CRYSTALS

2004 ◽  
Vol 18 (25) ◽  
pp. 1275-1291 ◽  
Author(s):  
EKMEL OZBAY ◽  
KAAN GUVEN ◽  
ERTUGRUL CUBUKCU ◽  
KORAY AYDIN ◽  
B. KAMIL ALICI
Keyword(s):  
Optical Properties ◽  
Photonic Crystals ◽  
Negative Refraction ◽  
Numerical Study ◽  
Effective Index ◽  
Index Of Refraction ◽  
Far Field ◽  
Two Dimensional ◽  
Flat Lens ◽  
Effective Index Of Refraction

In this article, we present an experimental and numerical study of novel optical properties of two-dimensional dielectric photonic crystals (PCs) which exhibit negative refraction. We investigate two mechanisms which utilize the band structure of the PC to generate a negative effective index of refraction (n eff <0) and demonstrate the negative refraction experimentally. To the isotropic extend of n eff , different PC slab structures are employed to focus the radiation of a point source. It is shown experimentally that the PC can generate an image of the source with subwavelength resolution in the vicinity of the PC interface. Using a different PC, one can also obtain a far field focusing. In the latter case, we explicitly show the flat lens behavior of the structure. These examples indicate that PC-based lenses can surpass limitations of conventional lenses and lead to novel optics applications.

scholarly journals The white-light humidified optical particle spectrometer (WHOPS) – a novel airborne system to characterize aerosol hygroscopicity

2014 ◽  
Vol 7 (7) ◽  
pp. 7321-7366 ◽  
Author(s):  
B. Rosati ◽  
G. Wehrle ◽  
P. Zieger ◽  
M. Gysel ◽  
U. Baltensperger ◽  
...  
Keyword(s):  
Optical Properties ◽  
Ammonium Sulfate ◽  
White Light ◽  
Laboratory Experiments ◽  
Effective Index ◽  
Index Of Refraction ◽  
Hygroscopic Growth ◽  
Airborne Measurements ◽  
New Instrument ◽  
Effective Index Of Refraction

Abstract. Aerosol particles experience hygroscopic growth at enhanced relative humidity (RH) which leads to changes in their optical properties. We developed the white-light humidified optical particle spectrometer (WHOPS), a new instrument to investigate the particles' hygroscopic growth. Here we present a detailed technical description and characterization of the WHOPS in laboratory and field experiments. The WHOPS consists of a differential mobility analyzer, a humidifier/bypass and a WELAS (white-light aerosol spectrometer) connected in series to provide fast measurements of particle hygroscopicity at sub-saturated RH and optical properties on airborne platforms. The WELAS employs a white-light source to minimize ambiguities in the optical particle sizing. In contrast to other hygroscopicity instruments, the WHOPS retrieves information of relatively large particles (i.e. diameter D > 280 nm), therefore investigating the more optically relevant size ranges. The effective index of refraction of the dry particles is retrieved from the optical diameter measured for size-selected aerosol samples with a well-defined dry mobility diameter. The data analysis approach for the optical sizing and retrieval of the index of refraction was extensively tested in laboratory experiments with polystyrene latex size standards and ammonium sulfate particles of different diameters. The hygroscopic growth factor (GF) distribution and aerosol mixing state is inferred from the optical size distribution measured for the size-selected and humidified aerosol sample. Laboratory experiments with pure ammonium sulfate particles revealed good agreement with Köhler theory (mean bias of ~ 3% and maximal deviation of 9% for GFs at RH = 95%). First airborne measurements in the Netherlands observed GFs (mean value of the GF distribution) at RH = 95% between 1.74 and 2.67 with a median of 1.94 for particles with a dry diameter of 500 nm. This corresponds to hygroscopicity parameters (κ) between 0.21 and 0.93 with a median of 0.33. The GF distributions indicate externally mixed particles covering the whole range of GFs between ~ 1.0–3.0. On average ~ 74% of the particles were "more hygroscopic" with GFs > 1.5, ~ 15% were non- or slightly hygroscopic with GF < 1.1 and the remaining ~ 11% were "less hygroscopic" with 1.1 < GF < 1.5. The more hygroscopic mode sometimes peaked at GF > 2, indicating influence of sea salt particles, consistent with previous ground-based particle hygroscopicity measurements in this area. The mean dry effective index of refraction for 500 nm particles was found to be rather constant with a value of 1.42 ± 0.04.

scholarly journals The white-light humidified optical particle spectrometer (WHOPS) – a novel airborne system to characterize aerosol hygroscopicity

2015 ◽  
Vol 8 (2) ◽  
pp. 921-939 ◽  
Author(s):  
B. Rosati ◽  
G. Wehrle ◽  
M. Gysel ◽  
P. Zieger ◽  
U. Baltensperger ◽  
...  
Keyword(s):  
Optical Properties ◽  
Ammonium Sulfate ◽  
White Light ◽  
Laboratory Experiments ◽  
Effective Index ◽  
Index Of Refraction ◽  
Hygroscopic Growth ◽  
Airborne Measurements ◽  
New Instrument ◽  
Effective Index Of Refraction

Abstract. Aerosol particles experience hygroscopic growth at enhanced relative humidity (RH), which leads to changes in their optical properties. We developed the white-light humidified optical particle spectrometer (WHOPS), a new instrument to investigate the particles' hygroscopic growth. Here we present a detailed technical description and characterization of the WHOPS in laboratory and field experiments. The WHOPS consists of a differential mobility analyzer, a humidifier/bypass and a white-light aerosol spectrometer (WELAS) connected in series to provide fast measurements of particle hygroscopicity at subsaturated RH and optical properties on airborne platforms. The WELAS employs a white-light source to minimize ambiguities in the optical particle sizing. In contrast to other hygroscopicity instruments, the WHOPS retrieves information of relatively large particles (i.e., diameter D > 280 nm), therefore investigating the more optically relevant size ranges. The effective index of refraction of the dry particles is retrieved from the optical diameter measured for size-selected aerosol samples with a well-defined dry mobility diameter. The data analysis approach for the optical sizing and retrieval of the index of refraction was extensively tested in laboratory experiments with polystyrene latex size standards and ammonium sulfate particles of different diameters. The hygroscopic growth factor (GF) distribution and aerosol mixing state is inferred from the optical size distribution measured for the size-selected and humidified aerosol sample. Laboratory experiments with pure ammonium sulfate particles revealed good agreement with Köhler theory (mean bias of ~3% and maximal deviation of 8% for GFs at RH = 95%). During first airborne measurements in the Netherlands, GFs (mean value of the GF distribution) at RH = 95% between 1.79 and 2.43 with a median of 2.02 were observed for particles with a dry diameter of 500 nm. This corresponds to hygroscopicity parameters (κ) between 0.25 and 0.75 with a median of 0.38. The GF distributions indicate externally mixed particles covering the whole range of GFs between ~1.0 and 3.0. On average, ~74% of the 500 nm particles had GFs > 1.5, ~15% had GF < 1.1 and the remaining ~1% showed values of 1.1 < GF < 1.5. The more hygroscopic mode sometimes peaked at GF > 2, indicating influence of sea-salt particles, consistent with previous ground-based particle hygroscopicity measurements in this area. The mean dry effective index of refraction for 500 nm particles was found to be rather constant with a value of 1.42 ± 0.04 (mean ± 1SD).

scholarly journals Hybrid Ag-LiNbO3 Nanocomposite Thin Films with Tailorable Optical Properties

2021 ◽  
Author(s):  
Jijie Huang ◽  
Di Zhang ◽  
Zhimin Qi ◽  
Bruce Zhang ◽  
Haiyan Wang
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Ag Nanoparticles ◽  
Photonic Device ◽  
Device Integration ◽  
Nanocomposite Thin Films

Ag nanostructures exhibit extraordinary optical properties, which are important for photonic device integration. Here, we deposited Ag-LiNbO3 (LNO) nanocomposite thin films with Ag nanoparticles (NPs) embedded into LNO matrix, by...

scholarly journals W:Al2O3 Nanocomposite Thin Films with Tunable Optical Properties Prepared by Atomic Layer Deposition

2016 ◽  
Vol 120 (27) ◽  
pp. 14681-14689 ◽  
Author(s):  
Shaista Babar ◽  
Anil U. Mane ◽  
Angel Yanguas-Gil ◽  
Elham Mohimi ◽  
Richard T. Haasch ◽  
...  
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Atomic Layer Deposition ◽  
Atomic Layer ◽  
Layer Deposition ◽  
Nanocomposite Thin Films ◽  
Tunable Optical Properties

The optical properties of Ag/ZnO nanocomposite thin films with different thickness

Optik ◽  
2017 ◽  
Vol 147 ◽  
pp. 6-13 ◽  
Author(s):  
Linhua Xu ◽  
Gaige Zheng ◽  
Yuzhu Liu ◽  
Jing Su ◽  
Wenjian Kuang ◽  
...  
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Nanocomposite Thin Films ◽  
Different Thickness

Microstructure and Optical Properties of Co Sputter Deposited Si-Al Nanocomposite Thin Films

2000 ◽  
Vol 648 ◽  
Author(s):  
F. Niu ◽  
P.J. Dobson ◽  
B. Cantor
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Optical Absorption ◽  
Absorption Peak ◽  
Al Content ◽  
Al Nanoparticles ◽  
Transmission Electron ◽  
Effective Medium Theories ◽  
Nanocomposite Thin Films ◽  
Sputter Deposited

AbstractNovel Si-Al nanocomposite thin films were made by radio frequency co-sputtering of Si and Al with Al content from 0 at.% to 69 at.%. Microstructure and optical properties of the films were characterised by conventional and high resolution transmission electron microscopyand spectrometry in the wavelength range from 200 to 3000 nm. The film microstructure consisted of Al nanoparticles (2-9 nm) embedded in an amorphous Si-Al matrix. Optical absorption spectra of the films up to 50 at.% Al exhibited a sharp absorption peak below500 nm and relatively low absorption above 500 nm. In addition, the absorption peak shifted towards longer wavelengths and the general absorption above 500 nm increased remarkably as Al content increased. For the Si-69at.%Al films, however, an absorption plateau appeared between 300 nm to 700 nm and a second weak and broad absorption peak appeared at around 900 nm. The results are analysed and compared with the optical absorption predicted by various effective medium theories.

Optical Propagation in Solids

2006 ◽  
Author(s):  
Michael E. Thomas
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Solid State ◽  
Optical Fibers ◽  
Optical Materials ◽  
Photonic Devices ◽  
Index Of Refraction ◽  
Optical Detectors ◽  
Optical Propagation ◽  
Valence Bands

This chapter emphasizes the linear optical properties of solids as a function of frequency and temperature. Such information is basic to understanding the performance of optical fibers, lenses, dielectric and metallic mirrors, window materials, thin films, and solid-state photonic devices in general. Optical properties are comprehensively covered in terms of mathematical models of the complex index of refraction based on those discussed in Chapters 4 and 5. Parameters for these models are listed in Appendix 4. A general review of solid-state properties precedes this development because the choice of an optical material requires consideration of thermal, mechanical, chemical, and physical properties as well. This section introduces the classification of optical materials and surveys other material properties that must be considered as part of total optical system design involving solidstate optics. Solid-state materials can be classified in several ways. The following are relevant to optical materials. Three general classes of solids are insulators, semiconductors, and metals. Insulators and semiconductors are used in a variety of ways, such as lenses, windows materials, fibers, and thin films. Semiconductors are used in electrooptic devices and optical detectors. Metals are used as reflectors and high-pass filters in the ultraviolet. This type of classification is a function of the material’s electronic bandgap. Materials with a large room-temperature bandgap (Eg > 3eV) are insulators. Materials with bandgaps between 0 and 3 eV are semiconductors. Metals have no observable bandgap because the conduction and valence bands overlap. Optical properties change drastically from below the bandgap, where the medium is transparent, to above the bandgap, where the medium is highly reflective and opaque. Thus, knowledge of its location is important. Appendix 4 lists the bandgaps of a wide variety of optical materials. To characterize a medium within the region of transparency requires an understanding of the mechanisms of low-level absorption and scattering. These mechanisms are classified as intrinsic or extrinsic. Intrinsic properties are the fundamental properties of a perfect material, caused by lattice vibrations, electronic transitions, and so on, of the atoms composing the material.

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