Search results for "Refractive"
showing 10 items of 559 documents
Absolute Chiral Sensing in Dielectric Metasurfaces Using Signal Reversals.
2020
Sensing molecular chirality at the nanoscale has been a long-standing challenge due to the inherently weak nature of chiroptical signals, and nanophotonic approaches have proven fruitful in accessing these signals. However, in most cases, absolute chiral sensing of the total chiral refractive index has not been possible, while the strong inherent signals from the nanostructures themselves obscure the weak chiroptical signals. Here, we propose a dielectric metamaterial system that overcomes these limitations and allows for absolute measurements of the total chirality, and the possibility for a crucial signal reversal that enables chirality measurements without the need for sample removal. As…
Thermo-optical studies of NaNbO3thin films
2007
Thermo-optical studies of sodium niobate NaNbO3 (NN) thin films, deposited by the pulsed laser ablation technique on Si/SrRuO3 substrates, were performed by spectroscopic ellipsometry in the temperature range 300-550°C. Optical constants at the room temperature were measured in the spectral range 250-1000 nm. Substantial changes in the refractive index temperature behaviour (taken at λ = 300 nm) were found at temperatures 370, 445, 503, 520, and 532°C, where the first and the last temperatures are the phase transitions P → R and S → T1, respectively. Other temperatures (445, 503, and 520°C) are suggested as the points of some local structural changes in the NN film.
Holographic recording in amorphous As2S3 films at 633nm
2006
Abstract Holographic grating recording with focused (light intensity I = 14–124 W/cm 2 ) and unfocused ( I = 0.50–0.78 W/cm 2 ) 633 nm He–Ne laser sub-bandgap light in non-annealed and annealed a-As 2 S 3 films has been experimentally studied. The focused light recording is found to be much more efficient (diffraction efficiency up to 14.9%, specific recording energy down to 216 J/(cm 2 %)) than the unfocused light recording (0.11%, 72 400 J/(cm 2 %)). Some other properties are also different. The hologram lifetime of more than two years and positive refractive index changes take place in the case of focused recording versus two days and negative refractive index changes for unfocused r…
Optical contrast of 2D InSe on SiO2/Si and transparent substrates using bandpass filters
2017
The particular optical and electronic properties recently reported for 2D InSe depict this 2D material as being very versatile for future electronic and optoelectronic devices with tunable and optimized functionalities. For its fundamental study and the development of practical applications, rapid and accurate identification methods of atomically thin InSe are essential. Here, we demonstrate an enhancement of the optical contrast between InSe nanosheets and the underlying SiO2/Si substrate by illuminating with a 40 nm wide bandpass filter centered at 500 nm. Moreover, we study the optical contrast of 2D InSe on transparent substrates. Our results suggest that a good optical contrast is achi…
Multiplexing of encrypted data using fractal masks
2012
In this Letter, we present to the best of our knowledge a new all-optical technique for multiple-image encryption and multiplexing, based on fractal encrypting masks. The optical architecture is a joint transform correlator. The multiplexed encrypted data are stored in a photorefractive crystal. The fractal parameters of the key can be easily tuned to lead to a multiplexing operation without cross talk effects. Experimental results that support the potential of the method are presented.
Refractive index of the CuAlO2delafossite
2008
The refractive index of the CuAlO2 delafossite has been determined from interference measurements in single crystals performed in the visible, near and mid infrared regions of the spectrum. The analysis of the refractive index dispersion corresponding to light polarization perpendicular to the c-axis (P ⊥ c) yields a static dielectric constant of 0 = 7.7 ± 0.8 and a low frequency electronic constant ∞ = 5.1 ± 0.1. The relevant infrared active mode is found to be at 550 ± 25 cm−1. The electronic contribution can be well described by a Penn gap at 39 000 ± 1000 cm−1. Both the refractive index and its dispersion are found to be smaller for P||c than for P ⊥ c.
Infrared and Raman spectroscopy of WO3 and CdWO4
2001
Abstract Infrared reflection and Raman spectroscopy have been applied to study the vibrational modes of tungsten trioxide (WO 3 ) and cadmium tungstate (CdWO 4 ). Kramers–Kronig relations are employed to yield the refractive index as well as TO and LO functions of these materials at frequencies from 50 to 1200 cm −1 . The symmetry of the vibrations of CdWO 4 is reported.
Visual and optical performance with hybrid multifocal intraocular lenses
2010
During the past years, the wish to become independent of spectacles has been growing among cataract and presbyopic patients due to many factors, such as the increase in near visual demands, the aesthetic need for a spectacle-free image and ageing of refractive surgery patients, among others. This review assesses recently published studies that analyse visual and optical performance through different metrics of eyes implanted with multifocal intraocular lenses (IOLs), particularly hybrid IOL designs. The published evidence suggests that hybrid multifocal IOLs provide very good outcomes in a number of visual and optical performance parameters. Patients implanted with this type of IOL obtain a…
Thermophysical properties of binary mixtures of 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ionic liquid with alcohols at several tempera…
2018
Abstract Densities, speeds of sound, and refractive indices for the binary systems made up by 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate and methanol, ethanol, 1-propanol, or 2-propanol, as well as for the pure components, have been measured covering the whole range of compositions at atmospheric pressure and T = (278.15–338.15) K. From densities and speeds of sound, isentropic compressibilities were calculated using the Newton-Laplace equation. Liquid ideal-mixture properties have been defined and calculated, and they have been used to determine excess molar volumes, excess isentropic compressibilities, and deviations in refractive indices. Excess and deviations in properties …
Integrated Optical Technique for Detection of Electro-Optical Non-Linearities in Thin Films
1976
A simple method for detection of electro-optical non-linearities in thin films is presented. The method involves an easily fabricated structure and a little practice in integrated optical techniques. It is also possible to detect small induced variations of refractive index, using lower voltage with respect to those applied in a conventional Kerr cell. We have sucessfully tested our method using two different polymer materials as thin films. In both of these we have observed an induced ?n ? 3 10?5 with an electric field of 60 V/?, with a response time round about 300 nsec. The experimental values of induced ?n versus electric field fit very well a parabola, proving the quadratic behavior of…