Development of Neutral-Density Infrared Filters Using Metallic Thin Films

1994 ◽  
Vol 374 ◽  
Author(s):  
Z. M. Zhang ◽  
R. U. Dada ◽  
L. M. Hanssen
Keyword(s):  
Optical Constants ◽  
Wavelength Region ◽  
Single Layer ◽  
Alloy Film ◽  
Neutral Density ◽  
Metallic Thin Films ◽  
Future Design ◽  
Infrared Spectrometer ◽  
Spectrometer Calibration ◽  
Reflectance Measurements

AbstractBroadband infrared filters with uniform spectral transmittance are used for spectrometer calibration and other applications. However, commercially available neutral-density filters with optical density (GD) greater than 2 exhibit significant variations in OD over the wavelength region from 2 μm to 25 μ m. In this work, we found a single-layer alloy film that, for appropriate thicknesses, yields a flat transmittance for OD near 3 and 4. The transmittance and reflectance of the filters were measured using a Fourier-transform infrared spectrometer. The optical constants of the alloy films were obtained from transmittance and reflectance measurements, which can be used for future design optimization.

Analysis of Cu(InGa)Se2 Alloy Film Optical Properties and the Effect of Cu Off-Stoichiometry

2005 ◽  
Vol 865 ◽  
Author(s):  
P. D. Paulson ◽  
S. H. Stephens ◽  
W. N. Shafarman
Keyword(s):  
Optical Constants ◽  
Soda Lime ◽  
Alloy Film ◽  
Relative Volume ◽  
Soda Lime Glass ◽  
Distinctive Features ◽  
Glass Substrates ◽  
Wide Range ◽  
Two Phases

AbstractVariable angle spectroscopic ellipsometry has been used to characterize Cu(InGa)Se2 thin films as a function of relative Ga content and to study the effects of Cu off-stoichiometry. Uniform Cu(InGa)Se2 films were deposited on Mo-coated soda lime glass substrates by elemental evaporation with a wide range of relative Cu and Ga concentrations. Optical constants of Cu(InGa)Se2 were determined over the energy range of 0.75–C4.6 eV for films with 0 ≤ Ga/(In+Ga) ≤ 1 and used to determine electronic transition energies. Further, the changes in the optical constants and electronic transitions as a function of Cu off-stoichiometry were determined in Cu-In-Ga-Se films with Cu atomic concentration varying from 10 to 25 % and Ga/(In+Ga) = 0.3. Films with Cu in the range 16–24 % are expected to contain 2 phases so an effective medium approximation is used to model the data. This enables the relative volume fractions of the two phases, and hence composition, to be determined. Two distinctive features are observed in the optical spectra as the Cu concentration decreases. First, the fundamental bandgaps are shifted to higher energies. Second, the critical point features at higher energies become broader suggesting degradation of the crystalline quality of the material.

Optical constants measurement of single-layer thin films on transparent substrates

1998 ◽  
Vol 158 (1-6) ◽  
pp. 221-230 ◽  
Author(s):  
A. Penzkofer ◽  
E. Drotleff ◽  
W. Holzer
Keyword(s):  
Thin Films ◽  
Optical Constants ◽  
Single Layer

Optical constants of e-beam-deposited zirconium dioxide measured in the 55–150 Å wavelength region using the reflectivity technique

2016 ◽  
Vol 55 (12) ◽  
pp. 3170 ◽  
Author(s):  
Amol Singh ◽  
Mangalika Sinha ◽  
R. K. Gupta ◽  
Mohammed H. Modi
Keyword(s):  
Zirconium Dioxide ◽  
Optical Constants ◽  
Wavelength Region

Optical constants of particulate minerals from reflectance measurements: The case of calcite

2006 ◽  
Vol 100 (1-3) ◽  
pp. 250-255 ◽  
Author(s):  
A.C. Marra ◽  
R. Politi ◽  
A. Blanco ◽  
R. Brunetto ◽  
S. Fonti ◽  
...  
Keyword(s):  
Optical Constants ◽  
Reflectance Measurements

Calculation of Spectral Optical Constants Using Combined Ellipsometric and Reflectance Methods for Smooth and Rough Bulk Samples

2021 ◽  
pp. 000370282110478
Author(s):  
Gilles Fortin
Keyword(s):  
Rough Surface ◽  
Optical Constants ◽  
Sample Surface ◽  
Infrared Region ◽  
Homogeneous Sample ◽  
Specular Reflectance ◽  
Scattering Effects ◽  
Spectral Ranges ◽  
Reflectance Measurements ◽  
Polarized Reflectance

Spectra of the optical constants n and k of a substance are often deduced from spectroscopic measurements, performed on a thick and homogeneous sample, and from a model used to simulate these measurements. Spectra obtained for n and k using the ellipsometric method generally produce polarized reflectance simulations in strong agreement with the experimental measurements, but they sometimes introduce significant discrepancies over limited spectral ranges, whereas spectra of n and k obtained with the single-angle reflectance method require a perfectly smooth sample surface to be viable. This paper presents an alternative method to calculate n and k. The method exploits both ellipsometric measurements and s-polarized specular reflectance measurements, and compensates for potential surface scattering effects with the introduction of a specularity factor. It is applicable to bulk samples having either a smooth or a rough surface. It provides spectral optical constants that are consistent with s-polarized reflectance measurements. Demonstrations are performed in the infrared region using a glass slide (smooth surface) and a pellet of compressed ammonium sulfate powder (rough surface).

Optical constants of silicon and silicon dioxide using soft X-ray reflectance measurements

2002 ◽  
Vol 211 (1-6) ◽  
pp. 215-223 ◽  
Author(s):  
Pragya Tripathi ◽  
G.S. Lodha ◽  
M.H. Modi ◽  
A.K. Sinha ◽  
K.J.S. Sawhney ◽  
...  
Keyword(s):  
Silicon Dioxide ◽  
Optical Constants ◽  
X Ray ◽  
Reflectance Measurements

Infrared Optical Constants from Pressed Pellets of Powders: I. Improved n and k Values of (NH4)2SO4 from Single-Angle Reflectance

2020 ◽  
Vol 74 (8) ◽  
pp. 851-867
Author(s):  
Timothy J. Johnson ◽  
Emmanuela Diaz ◽  
Kendall D. Hughey ◽  
Tanya L. Myers ◽  
Thomas A. Blake ◽  
...  
Keyword(s):  
Optical Constants ◽  
Complex Refractive Index ◽  
Optical Quality ◽  
Substantial Improvement ◽  
Index Formula ◽  
Pressing Pressure ◽  
Void Space ◽  
Specular Reflectance ◽  
Pellet Formation ◽  
Infrared Spectrometer

In combination with other parameters, the real, n([Formula: see text]), and imaginary, k([Formula: see text]), components of the complex refractive index, [Formula: see text] =  n + i k, can be used to simulate the optical properties of a material in different forms, e.g., its infrared spectra. Ultimately, such n/k values can be used to generate a database of synthetic reflectance spectra for the different morphologies to which experimental data can be compared. But obtaining reliable values of the optical constants n/k for solid materials is challenging due to the lack of optical quality specimens, usually crystals, large enough to measure. An alternative to crystals is to press the powder into a uniform disk. We have produced pellets from ammonium sulfate, (NH4)2SO4, powder and derived the pellets' n and k values via single-angle reflectance using a specular reflectance device in combination with a Fourier transform infrared spectrometer. The single-angle technique measures amplitude of light reflected from the material as a function of wavelength over a wide spectral domain; the optical constants are determined from the reflectance data using the Kramers–Kronig relationship. We investigate several parameters associated with the pellets and pellet formation and their effects upon delivering the most reliable n/k values. Parameters studied include pellet diameter, mass, and density (void space), drying, grinding, sieving, and particle size in the pellet formation, as well as pressing pressure and duration. Of these parameters, using size-selected mixtures of dried, small (<50 µm) particles and pressing at ≥10 tons for at least 30 min were found key to forming highly reflective samples. Comparison of two sets of previous literature n([Formula: see text]) and k([Formula: see text]) values obtained from crystalline (NH4)2SO4 both as crystal reflectance as well as extinction spectra of aerosols measured in a flow tube shows reasonable agreement, but suggests the present values, as confirmed from two independent techniques, represent a substantial improvement for n/k values for (NH4)2SO4, also demonstrating promise to measure the optical constants of other materials.

Sign in / Sign up

Export Citation Format

Share Document