scholarly journals Structural Coloration in Caloenas Nicobarica Pigeons and Refractive Index Modulated Sensing

2018 ◽  
Vol 6 (9) ◽  
pp. 1701218 ◽  
Author(s):  
Ijaz Rashid ◽  
Muhammad Umair Hassan ◽  
Abbas Khandwalla ◽  
Rayan Mohammed Ameen ◽  
Ali Kemal Yetisen ◽  
...  
Keyword(s):  
Refractive Index ◽  
Structural Coloration

Spectral reflectance and directional properties of structural coloration in bird plumage

2002 ◽  
Vol 205 (14) ◽  
pp. 2017-2027 ◽  
Author(s):  
D. Osorio ◽  
A. D. Ham
Keyword(s):  
Refractive Index ◽  
Spectral Tuning ◽  
Fixed Position ◽  
Constructive Interference ◽  
Structural Coloration ◽  
Spectrally Selective ◽  
Optical Effects ◽  
Selective Interference ◽  
Visual Properties ◽  
Low Refractive Index

SUMMARY Bird plumage is coloured both by pigments and by spectrally selective interference in the light reflected from feather barbs. These barbs are composites of high- and low-refractive-index materials, and light is reflected at refractive index boundaries. The spatial structure determines the wavelengths where constructive interference occurs and, hence, the spectral tuning. The spectral tuning of interference colours often varies with angles of illumination and reflection, which produces iridescence. Iridescence and other optical effects mean that interference coloration looks different from pigmentation and is visually striking. To study the optical and visual properties of structural plumage colours, we recorded the reflectance spectra of feathers and in particular their directional properties. A fixed spot on a feather was viewed from a fixed position, whilst the feather orientation and the angle of illumination were varied. We recognise two main types of coloration, `directional' and `diffuse'. Within these types, there is considerable variation, and five examples illustrate some features of structural plumage colours and suggest how their optical and visual properties can be measured and described.

scholarly journals The Ultrastructure of the Epicuticular Interference Reflectors of Tiger Beetles (Cicindela)

1985 ◽  
Vol 117 (1) ◽  
pp. 87-110
Author(s):  
T.D. SCHULTZ ◽  
M.A. RANKIN
Keyword(s):  
Refractive Index ◽  
Dense Material ◽  
Dense Layer ◽  
Surface Reflectance ◽  
Structural Coloration ◽  
Electron Dense Material ◽  
Tiger Beetles ◽  
Electron Lucent

Tiger beetles of the genus Cicindela exhibit iridescent structural coloration due to the presence of a non-ideal multilayer interference reflector located in the outermost 2 μm of the integument. The reflector is composed of alternating layers of electron-lucent and electron-dense material. This series of layers was distinguished from chitinous procuticle by its position, ultrastructure and solubility in dilute KOH. The reflector appears homologous with the inner epicuticle of current models. Measurements of surface reflectance, refractive index and the dimensions of the alternating layers suggests that the dense layer has a refractive index (RI) near 2.0 and may be a melanoprotein.

TEM characterization of proton-exchanged LiNbO3 optical waveguides

1986 ◽  
Vol 44 ◽  
pp. 480-481
Author(s):  
W. E. Lee
Keyword(s):  
Refractive Index ◽  
Benzoic Acid ◽  
Optical Waveguides ◽  
Total Internal Reflection ◽  
Index Of Refraction ◽  
Optical Measurements ◽  
Lithium Ions ◽  
Wide Channel ◽  
Tem Characterization

An optical waveguide consists of a several-micron wide channel with a slightly different index of refraction than the host substrate; light can be trapped in the channel by total internal reflection.Optical waveguides can be formed from single-crystal LiNbO3 using the proton exhange technique. In this technique, polished specimens are masked with polycrystal1ine chromium in such a way as to leave 3-13 μm wide channels. These are held in benzoic acid at 249°C for 5 minutes allowing protons to exchange for lithium ions within the channels causing an increase in the refractive index of the channel and creating the waveguide. Unfortunately, optical measurements often reveal a loss in waveguiding ability up to several weeks after exchange.

Light microscopy of ceramics

1993 ◽  
Vol 51 ◽  
pp. 908-909
Author(s):  
Walter C. McCrone
Keyword(s):  
Refractive Index ◽  
Light Microscopy ◽  
Light Microscope ◽  
Polarized Light ◽  
Refractive Indices ◽  
Complete Coverage ◽  
The Subject ◽  
Lower Refractive Index

An excellent chapter on this subject by V.D. Fréchette appeared in a book edited by L.L. Hench and R.W. Gould in 1971 (1). That chapter with the references cited there provides a very complete coverage of the subject. I will add a more complete coverage of an important polarized light microscope (PLM) technique developed more recently (2). Dispersion staining is based on refractive index and its variation with wavelength (dispersion of index). A particle of, say almandite, a garnet, has refractive indices of nF = 1.789 nm, nD = 1.780 nm and nC = 1.775 nm. A Cargille refractive index liquid having nD = 1.780 nm will have nF = 1.810 and nC = 1.768 nm. Almandite grains will disappear in that liquid when observed with a beam of 589 nm light (D-line), but it will have a lower refractive index than that liquid with 486 nm light (F-line), and a higher index than that liquid with 656 nm light (C-line).

On the refractive index of rutile

1992 ◽  
Vol 139 (2) ◽  
pp. 163 ◽  
Author(s):  
M.R. Shenoy ◽  
R.M. de la Rue
Keyword(s):  
Refractive Index

Modification of optical properties of PC-PBT/Cr2O3 and PC-PBT/CdS nanocomposites by gamma irradiation

2020 ◽  
Vol 92 (2) ◽  
pp. 20402
Author(s):  
Kaoutar Benthami ◽  
Mai ME. Barakat ◽  
Samir A. Nouh
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Band Gap ◽  
Color Difference ◽  
Band Gap Energy ◽  
Polybutylene Terephthalate ◽  
Γ Irradiation ◽  
Gap Energy ◽  
Vis Spectroscopy ◽  
Oxygen Atoms

Nanocomposite (NCP) films of polycarbonate-polybutylene terephthalate (PC-PBT) blend as a host material to Cr2O3 and CdS nanoparticles (NPs) were fabricated by both thermolysis and casting techniques. Samples from the PC-PBT/Cr2O3 and PC-PBT/CdS NCPs were irradiated using different doses (20–110 kGy) of γ radiation. The induced modifications in the optical properties of the γ irradiated NCPs have been studied as a function of γ dose using UV Vis spectroscopy and CIE color difference method. Optical dielectric loss and Tauc's model were used to estimate the optical band gaps of the NCP films and to identify the types of electronic transition. The value of optical band gap energy of PC-PBT/Cr2O3 NCP was reduced from 3.23 to 3.06 upon γ irradiation up to 110 kGy, while it decreased from 4.26 to 4.14 eV for PC-PBT/CdS NCP, indicating the growth of disordered phase in both NCPs. This was accompanied by a rise in the refractive index for both the PC-PBT/Cr2O3 and PC-PBT/CdS NCP films, leading to an enhancement in their isotropic nature. The Cr2O3 NPs were found to be more effective in changing the band gap energy and refractive index due to the presence of excess oxygen atoms that help with the oxygen atoms of the carbonyl group in increasing the chance of covalent bonds formation between the NPs and the PC-PBT blend. Moreover, the color intensity, ΔE has been computed; results show that both the two synthesized NCPs have a response to color alteration by γ irradiation, but the PC-PBT/Cr2O3 has a more response since the values of ΔE achieved a significant color difference >5 which is an acceptable match in commercial reproduction on printing presses. According to the resulting enhancement in the optical characteristics of the developed NCPs, they can be a suitable candidate as activate materials in optoelectronic devices, or shielding sheets for solar cells.

Refractive Index for Atomic Waves: Theory and Detailed Calculations

1997 ◽  
Vol 7 (4) ◽  
pp. 523-541 ◽  
Author(s):  
C. Champenois ◽  
E. Audouard ◽  
P. Duplàa ◽  
J. Vigué
Keyword(s):  
Refractive Index
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