scholarly journals A contribution to the study of the optical properties of mixed crystals

1925 ◽  
Vol 109 (749) ◽  
pp. 78-98 ◽  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Linear Function ◽  
Mixed Crystal ◽  
Mixed Crystals ◽  
Refractive Indices ◽  
Axial Angle ◽  
Quantitative Results ◽  
The Mean ◽  
At Will

The optical properties of isomorphous mixtures produced in the laboratory have been studied by various crystallographers since the time of Senarmont, who found that the optic axial angle of mixtures of the potassium and ammonium-seignette salts was intermediate between those of the simple salts and varied gradually with the composition of the mixtures. Such artificially prepared mixtures offer better material for investigation than do the mixtures occurring as minerals, since their composition is simpler and can be varied at will. The first quantitative results were obtained by Dufet, who measured the mean refractive index (β) of mixtures of the orthorhombic sulphates of magnesium and nickel and enunciated the law: "The differences between the refractive indices of a mixture of two isomorphous salts and those of the component salts are inversely proportional to the numbers of molecules of the two salts in the mixture.” This is equivalent to the statement that in (orthorhombic) mixed crystals the refractive index of a mixture is a linear function of its composition as expressed in molecular percentage. Thus, if N n' n" are the refractive indices of the mixed crystal and of the two components, respectively, and m' m" are the molecular percentages of the two components N = m'n' + m"n" /100.

Optical properties of a liquid crystal with small ordinary and extraordinary refractive indices and small optical anisotropy

2014 ◽  
Vol 22 (3) ◽  
Author(s):  
J. Kędzierski ◽  
K. Garbat ◽  
Z. Raszewski ◽  
M. Kojdecki ◽  
K. Kowiorski ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Liquid Crystal ◽  
Optical Anisotropy ◽  
Order Parameter ◽  
Orientational Order ◽  
Refractive Indices ◽  
Orientational Order Parameter ◽  
Unknown Density ◽  
Abbe Refractometer

AbstractOptical properties of a nematic liquid crystal with small refractive index and small birefringence were studied. The ordinary and extraordinary refractive indices and birefringence were measured as functions of temperature by using an Abbe refractometer and wedge nematic cells. From values of these indices the nematic orientational order parameter was calculated by using several methods and corresponding mathematical models. Kuczyński et al. method was found to be suitable for determining the order parameter also for materials featuring small ordinary refractive index, with unknown density.

The use of a slit in determining refractive indices with the microscope

1917 ◽  
Vol 18 (84) ◽  
pp. 130-132
Author(s):  
John William Evans
Keyword(s):  
Crystal Structure ◽  
Refractive Index ◽  
Optical Properties ◽  
Critical Angle ◽  
Total Reflection ◽  
Index Of Refraction ◽  
Refractive Indices ◽  
Object Image ◽  
Ordinary Object

Certain optical properties of crystals, and more particularly the refractive index, may be determined either in the directions-image, often referred to as the 'image in convergent light', or in the ordinary object-image in which the object itself is seen. In the former case, in which the index of refraction is 'usually determined by means of the critical angle of total-reflection, every point in the image corresponds to a single direction of propagation of the wave-front through the crystal-structure and to the two corresponding directions of vibration. One of these can, however, be eliminated by the insertion of a nicol in an approximate position, and thus all ambiguity in the determination of the refractive index is removed.

Optical Properties of AlGaAsSb, AlGalnP, AlGaInAs, and GaInAsP for Optoelectronic Applications

1999 ◽  
Vol 579 ◽  
Author(s):  
M. Linnik ◽  
A. Christou
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Interband Transition ◽  
Theoretical Data ◽  
Quaternary Alloy ◽  
Refractive Indices ◽  
Incident Wavelength ◽  
Semiconductor Alloy ◽  
Transparent Region ◽  
Semi Empirical

ABSTRACTThe authors present calculations of quaternary III–V semiconductor alloy optical properties and the comparison of the theoretical data with available experimental results for AlGaAsSb, AlGaInP, AlGaInAs, and GaInAsP alloys. The investigation includes material's energy bandgap and refractive index calculations as a function of the incident wavelength in the transparent region, as well as the composition of the alloy. Optimization of the quaternary alloy refractive indices was obtained from a semi-empirical dielectric function calculations based on the interband transition contributions.

Optical Properties of Low Dielectric Constant Polyimides and Effects of Orientation

1993 ◽  
Vol 323 ◽  
Author(s):  
David C. Rich ◽  
Peggy Cebe ◽  
Anne K. St. Clair
Keyword(s):  
Dielectric Constant ◽  
Refractive Index ◽  
Optical Properties ◽  
Fluorine Content ◽  
Polymer Chains ◽  
Low Dielectric Constant ◽  
Refractive Indices ◽  
Electronic Polarizability ◽  
Low Dielectric ◽  
Preferential Alignment

AbstractControl of the refractive index in low dielectric constant polyimides through modification of chemistry and structure was investigated. The optical refractive indices of several low dielectric constant polyimides were measured, and the effects of orientation on optical anisotropy were determined. Refractive index in these polyimides was found to decrease with increasing fluorine content due primarily to the low electronic polarizability of the fluorine-carbon bonds. In zone drawn polyimides, refractive index was found to increase substantially in the direction of the draw, but decrease substantially normal to the draw direction. This was explained in terms of the preferential alignment of the polymer chains.

scholarly journals Remote sensing of soot carbon – Part 1: Distinguishing different absorbing aerosol species

2015 ◽  
Vol 15 (9) ◽  
pp. 13607-13656 ◽  
Author(s):  
G. L. Schuster ◽  
O. Dubovik ◽  
A. Arola
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Iron Oxide ◽  
South America ◽  
Biomass Burning ◽  
Southern Africa ◽  
Refractive Indices ◽  
Carbonaceous Aerosols ◽  
Fine Mode ◽  
Soot Carbon

Abstract. We describe a method of using the aerosol robotic network (AERONET) size distributions and complex refractive indices to retrieve the relative proportion of carbonaceous aerosols and iron oxide minerals. We assume that soot carbon has a spectrally flat refractive index, and that enhanced imaginary indices at the 440 nm wavelength are caused by brown carbon or hematite. Carbonaceous aerosols can be separated from dust in imaginary refractive index space because 95% of biomass burning aerosols have imaginary indices greater than 0.0042 at the 675–1020 nm wavelengths, and 95% of dust has imaginary refractive indices of less than 0.0042 at those wavelengths. However, mixtures of these two types of particles can not be unambiguously partitioned on the basis of optical properties alone, so we also separate these particles by size. Regional and seasonal results are consistent with expectations. Monthly climatologies of fine mode soot carbon are less than 1.0% by volume for West Africa and the Middle East, but the southern Africa and South America biomass burning sites have peak values of 3.0 and 1.7%. Monthly-averaged fine mode brown carbon volume fractions have a peak value of 5.8% for West Africa, 2.1% for the Middle East, 3.7% for southern Africa, and 5.7% for South America. Monthly climatologies of iron oxide volume fractions show little seasonal variability, and range from about 1.1 to 1.7% for coarse mode aerosols in all four study regions. Finally, our sensitivity study indicates that the soot carbon retrieval is not sensitive to the component refractive indices or densities assumed for carbonaceous and iron oxide aerosols, and differs by only 15.4% when these parameters are altered from our chosen baseline values. The associated soot carbon absorption aerosol optical depth (AAOD) does not vary at all when these parameters are altered, however, because the retrieval is constrained by the AERONET optical properties.

The Size of Living Bacteria

1957 ◽  
Vol s3-98 (44) ◽  
pp. 435-454
Author(s):  
K.F. A. ROSS
Keyword(s):  
Refractive Index ◽  
Phase Change ◽  
Direct Measurement ◽  
Lactobacillus Bulgaricus ◽  
Refractive Indices ◽  
Interference Microscope ◽  
The Mean ◽  
Different Cultures ◽  
Thickness Measurements ◽  
Living Bacteria

The difficulties involved in the direct measurement, by eyepiece-micrometer or from photomicrographs, of small microscopic objects such as living bacteria are discussed. The accuracy with which this can be done is limited by the numerical aperture of the optical system and the wavelength of light used. With visible light it is scarcely possible to determine the dimensions of an object more accurately than to the nearest 0.4µ. It also seems probable, from the nature of the diffraction pattern at the edges of images of objects of circular cross-section such as bacteria, that direct measurement of the width of the image will tend to give an underestimate of the true width of the object. An interference microscope enables thickness measurements to be made that are not subject to these particular limitations, because with it, the phase-change in the light passing through the middle of a bacterium can be measured very accurately. This phase-change is proportional to the product of the refractive index of the bacterium minus that of the mounting medium, and its true thickness. Two methods were used to determine the mean thickness of the living bacilli in a number of different cultures of Lactobacillus bulgaricus. With the first, the mean refractive index of the bacilli was measured directly by the method of immersion refractometry first used by Barer and Ross (1952), and phase-change measurements were made on the bacilli mounted in dilute saline. Their mean thickness was calculated from these measurements. With the second method, phase-change measurements were made on the bacilli mounted in saline and also mounted in protein solutions with refractive indices ranging from 1.365 to 1.376; and, from these, both their mean thickness and their mean refractive index were calculated. The phase-change measurements were made with a Smith interference microscope and half-shade eyepiece (manufactured by Messrs. Charles Baker). The values for the mean thickness of the living L. bulgaricus from 14 different cultures obtained by the first method ranged from 1·13 µ to 1·23 µ; and those from 9 different cultures obtained by the second method ranged from 1·02 µ to 1·14 µ. The mean refractive indices of the latter calculated by the second method agreed very closely with that obtained by immersion refractometry, and differed by a maximum of 0.009 in all the cultures measured. It therefore seems unlikely that the mean thickness measurements obtained by either method are wrong by more than about ±0.1 µ.

Optical properties of arsenic trisulphide

1967 ◽  
Vol 297 (1449) ◽  
pp. 230-243 ◽  
Keyword(s):  
Optical Properties ◽  
Absorption Spectrum ◽  
High Energy ◽  
Refractive Indices ◽  
Optical Absorption Spectra ◽  
Absorption Bands ◽  
Axial Angle ◽  
Transmission Measurements ◽  
Additional Maximum ◽  
Good Agreement

The optical absorption spectra ( E || c , E ⊥ c ) of As 2 S 3 have been determined from transmission measurements on single crystals ranging in thickness from 550 to 0·07 μm, At 77 °K the absorption spectrum ( E || c ) consists of three absorption bands A, B and C at 23300, 24100 and 25600 cm -1 respectively. The absorption bands for E ⊥ c occur 500 cm -1 to the high energy side of those for E || c . The variation of absorption coefficient α with photon energy hv at the absorption edge (290°K) can be resolved into four regions each of which is described by the equation α = a ( hv + b ) 2 . At 290 and 77°K the single crystal reflexion spectra ( E || c , E ⊥ c ) show maxima associated with the absorption bands and an additional maximum at 35000 cm -1 . The calculated and measured reflectivities are in good agreement. Measurements have been made of the dispersion of the principal refractive indices and of the optic axial angle. The spectral distribution of photocurrent shows peaks associated with absorption bands B and C ( E || c , E ⊥ c ).

scholarly journals Determining the infrared radiative effects of Saharan dust: a radiative transfer modelling study based on vertically resolved measurements at Lampedusa

2017 ◽  
Author(s):  
Daniela Meloni ◽  
Alcide di Sarra ◽  
Gérard Brogniez ◽  
Cyrielle Denjean ◽  
Lorenzo De Silvestri ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Size Distribution ◽  
Radiative Forcing ◽  
Refractive Indices ◽  
Radiative Effects ◽  
Brightness Temperatures ◽  
Dust Size Distribution ◽  
Aerosol Properties

Abstract. Detailed atmospheric and aerosol properties, and radiation measurements were carried out in summer 2013 during the Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region (ADRIMED) campaign in the framework of the Chemistry-Aerosol Mediterranean Experiment (ChArMEx) experiment. This study focusses on the characterization of infrared (IR) optical properties and direct radiative effects of mineral dust, based on three vertical profiles of atmospheric and aerosol properties and IR broadband and narrowband radiation from airborne measurements, made in conjunction with radiosonde and ground-based observations at Lampedusa, in the central Mediterranean. Satellite IR spectra from IASI are also included in the analysis. The atmospheric and aerosol properties are used as input to a radiative transfer model, and various IR radiation parameters (upward and downward irradiance, nadir and zenith brightness temperature at different altitudes) are calculated and compared with observations. The model calculations are made for different sets of dust size distribution and refractive indices, derived from observations and from the literature. The main results of the analysis are that the IR dust radiative forcing is non negligible, and strongly depends on size distribution (SD) and refractive index (RI). When calculations are made using the in situ measured size distribution, it is possible to identify the refractive index that produces the best match with observed IR irradiances and brightness temperatures (BTs). The most appropriate refractive indices correspond to those determined from independent measurements of mineral dust aerosols from the source regions (Tunisia, Algeria, Morocco) of dust transported over Lampedusa, suggesting that differences in the source properties should be taken into account. With the in situ size distribution and the most appropriate refractive index the estimated dust IR radiative forcing efficiency is +23.7 W m-2 at the surface, -7.9 W m-2 within the atmosphere, and +15.8 W m-2 at the top of the atmosphere. The use of column integrated dust SD from AERONET may also produce a good agreement with measured irradiances and BTs, but with significantly different values of the RI. This implies large differences, up to a factor of 2.5 at surface, in the estimated dust radiative forcing, and in the IR heating rate. This study shows that spectrally resolved measurements of brightness temperatures are important to better constrain the dust IR optical properties, and to obtain a reliable estimate of its radiative effects. Efforts should be directed at obtaining an improved description of the dust size distribution, its vertical distribution, and at including regionally-resolved optical properties.

scholarly journals Quantitative interferometric measurements of the refractive index and its applications

2021 ◽  
Author(s):  
Mohammed Yahya
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Human Blood ◽  
Medical Science ◽  
Medical Diagnostics ◽  
Blood Analysis ◽  
Optical Systems ◽  
Refractive Indices ◽  
Contact Method

Optical interferometry is a non-contact method used for the imaging and measurement of the optical properties of small or large objects with nanoscale accuracy. Interferometers are essential optical systems in engineering and medical science and are generally used to measure refractive index changes, cell pathology and shape irregularities. The ability to provide quantitative, non-invasive measurements makes interferometers suitable candidates for the study of living cells in vivo and in vitro applications. In this study, a simple interferometric system capable of providing precise measurements of the refractive indices of transparent and semi-transparent mediums was designed and developed based on the Mach-Zehnder arrangement. During the development phase, the system was used to take precise measurements of the contrast factors of the three hydrocarbon components 1,2,3,4-Tetrtahydronaphtalenene (THN), Isobutylbenzen (IBB), and Dodecane (nC12), prepared in the laboratory. The results were also compared with the corresponding results obtained using the Abbemat refractometer. The results were in agreement with those obtained from both techniques as well as the results obtained from the literature, confirming the accuracy of the measurements obtained with the new system with deviations of ± 2.50×10-3. Blood analysis is a routine procedure used in medical diagnostics to confirm a patient’s condition. Measuring the optical properties of blood is difficult due to the non-homogenous nature of the blood itself. In addition, there is a lot of variation in the refractive indices reported in the literature. These are the reasons that motivated this research to develop an empirical model that can be used to predict the refractive index of human blood as a function of concentration, temperature and wavelength. The experimental measurements were conducted on mimicking phantom, that shows better stability compared to human blood, using the Abbemat Refractometer. The values obtained using the model was in substantial agreement with those obtained experimentally with standard deviations of ± 2.33×10-3. Once the accuracy of the interferometric system was confirmed, the system was used to study the refractive index and morphology of human red blood cells. The results of the analysis confirmed the system’s ability to determine refractive index and/or blood hematocrit values with appropriate clinical accuracy.

A comparative crystallographical study of the double selenates of the series R 2 M(SeO 4 ) 2 , 6H 2 O.—Part I. Salts in which M is zinc

1900 ◽  
Vol 66 (424-433) ◽  
pp. 248-250
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Physical Constants ◽  
Axial Angle ◽  
Large Numbers ◽  
Angle Orientation ◽  
Double Sulphates

In this communication are presented the results of the investigation of the group of salts of the above series in which M is represented by zinc, R being represented by potassium, rubidium, and cæsium. The investigation is similar to that which has previously been carried out for the double sulphates of the analogous series. The work consists of very large numbers of measurements of the exterior angles of the crystals, determinations of density, refractive index, optic axial angle, orientation of optical ellipsoid, and effect of change of temperature on the optical properties, together with the calculation of all the morphological and physical constants derivable from the measurements.

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