scholarly journals Crossing the light line

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
John Pendry ◽  
Paloma Huidobro ◽  
Mario Silveirinha ◽  
Emanuele Galiffi
Keyword(s):  
Refractive Index ◽  
Wave Model ◽  
Pulse Amplitude ◽  
Propagation Direction ◽  
Effective Medium Approximation ◽  
Speed Of Light ◽  
Bloch Waves ◽  
Light Line ◽  
Light Barrier ◽  
Constant Refractive Index

Abstract We ask the question “what happens to Bloch waves in gratings synthetically moving at near the speed of light?”. First we define a constant refractive index (CRI) model in which Bloch waves remain well defined as they break the light barrier, then show their dispersion rotating through 360° from negative to positive and back again. Next we introduce the effective medium approximation (EMA) then refine it into a 4-wave model which proves to be highly accurate. Finally using the Bloch waves to expand a pulse of light we demonstrate sudden inflation of pulse amplitude combined with reversal of propagation direction as a luminal grating is turned on.

A Theorem on Ray Trajectories

1968 ◽  
Vol 1 (3) ◽  
pp. 107-108
Author(s):  
K.C. Westfold
Keyword(s):  
Refractive Index ◽  
Specific Intensity ◽  
Snell’S Law ◽  
Ray Trajectories ◽  
Snell's Law ◽  
Constant Refractive Index

The classical theorems on the intensity of radiation (e.g. Milne) depend on the geometry of rectilinear ray trajectories in uniform media. In particular, the theorem concerning the specific intensity I in a medium specified by an isotropic refractive index μ—that, where there are no gains due to emission or losses due to absorption or scattering, the quantity I/μ2 = constant—is proved by assuming that the medium consists of a series of regions of constant refractive index at whose plane interfaces the coefficients of reflection are zero. For these the geometry of the trajectories (Figure 1) is such that, by Snell’s law,

Determination of 2V from one extinction curve and its related n0 curve

1963 ◽  
Vol 33 (263) ◽  
pp. 679-692 ◽  
Author(s):  
N. Joel
Keyword(s):  
Refractive Index ◽  
Extinction Curve ◽  
Biaxial Crystal ◽  
Principal Axes ◽  
Index Curve ◽  
Constant Refractive Index

SummaryFrom the extinction curve of a biaxial crystal mounted on a spindle stage (or one-axis stage goniometer), the related n0 curve can be derived and drawn on the stereogram. The n0 curve is the equivibration curve—or constant-refractive-index curve—that goes through the projection P0 of the spindle-stage axis. After the principal diameters (maximum 2η and minimum 2ζ) of the no curve have been measured, the angle 2V may be calculated by means of the formula cos V = sin ζ/sin η. This method can also be used for determining—or refining—the directions of the principal axes α, β, γ.

scholarly journals Complex refractive index of concentrated magnetic fluids

2018 ◽  
Vol 185 ◽  
pp. 09007
Author(s):  
Constantine Yerin ◽  
Victoria Lykhmanova ◽  
Marina Erina
Keyword(s):  
Refractive Index ◽  
Complex Refractive Index ◽  
Magnetic Fluids ◽  
Effective Medium ◽  
Effective Medium Approximation ◽  
The Real ◽  
Phase Concentration

The spectra of the real and imaginary parts of the refractive index of magnetic fluids based on kerosene with a solids phase concentration of 1% to 35% are experimentally measured. The comparison of calculations results have been made according to Maxwell-Garnett and Bruggeman’s models of effective medium approximation. The influence of refractive index spectra on the extinction of light in magnetic fluids is shown.

Infrared Refractive Index of Thin YBa2Cu307 Superconducting Films

1992 ◽  
Vol 114 (3) ◽  
pp. 644-652 ◽  
Author(s):  
Z. M. Zhang ◽  
B. I. Choi ◽  
T. A. Le ◽  
M. I. Flik ◽  
M. P. Siegal ◽  
...  
Keyword(s):  
Refractive Index ◽  
Complex Refractive Index ◽  
Wavelength Region ◽  
Wave Theory ◽  
Superconducting Films ◽  
High Tc ◽  
Thin Film Optics ◽  
Infrared Spectrometer ◽  
Thickness Independent ◽  
Constant Refractive Index

This work investigates whether thin-film optics with a constant refractive index can be applied to high-Tc superconducting thin films. The reflectance and transmittance of YBa2Cu3O7 films on LaAlO3 substrates are measured using a Fourier-transform infrared spectrometer at wavelengths from 1 to 100 μm at room temperature. The reflectance of these superconducting films at 10 K in the wavelength region from 2.5 to 25 μm is measured using a cryogenic reflectance accessory. The film thickness varies from 10 to 200 nm. By modeling the frequency-dependent complex conductivity in the normal and superconducting states and applying electromagnetic-wave theory, the complex refractive index of YBa2Cu3O7 films is obtained with a fitting technique. It is found that a thickness-independent refractive index can be applied even to a 25 nm film, and average values of the spectral refractive index for film thicknesses between 25 and 200 nm are recommended for engineering applications.

Controllability And Homogeneity Of Optical Properties Of Thin Porous Silicon Films

1997 ◽  
Vol 486 ◽  
Author(s):  
S. Uehara ◽  
T. Kubo ◽  
S. Ogata ◽  
T. Sato ◽  
J. Hosono ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Porous Silicon ◽  
Optical Thickness ◽  
Wavelength Dependence ◽  
Effective Medium Approximation ◽  
Electrode Position ◽  
High Porosity ◽  
Optical Homogeneity ◽  
Reflection Spectroscopy

AbstractReflection spectroscopy was applied to evaluate the optical homogeneity and the refractive index of thin porous silicon (PS) layer. Variation in PS layer optical thickness was evaluated by measuring and mapping the reflectance over the surface area. For the circular anodization area of 17 mm diameter, the measured variation was less than 5 % on an area of 11 mm diameter. The anodization electrode position was found to have little influence on the homogeneity. A method to derive refractive index from a reflection spectrum is studied. The wavelength dependence of PS index measured by the method showed fair coincidence with the calculation based on effective medium approximation. In the two layer PS formation, optical thickness was found to change whether high porosity or low porosity layer is formed first.

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