Search results for "Refractive"
showing 10 items of 559 documents
Accurate mode characterization of two-mode optical fibers by in-fiber acousto-optics.
2016
Acousto-optic interaction in optical fibers is exploited for the accurate and broadband characterization of two-mode optical fibers. Coupling between LP01 and LP1m modes is produced in a broadband wavelength range. Difference in effective indices, group indices, and chromatic dispersions between the guided modes, are obtained from experimental measurements. Additionally, we show that the technique is suitable to investigate the fine modes structure of LP modes, and some other intriguing features related with modes' cut-off.
Nonlinear pulse deceleration using photorefractive four-wave mixing
2009
We investigate the possibilities of the backward four-wave coupling based on the nonlocal photorefractive response for the nonlinear deceleration of light pulses. The presence of an additional external variable parameter—the pump intensity ratio—allows to improve the output characteristics of the decelerated pulses compared to those typical of the two-wave coupling. In particular, large delay times of the output pulses can be achieved without their strong amplification. This positive distinctive feature of the pulse deceleration occurs far from threshold of the mirrorless optical oscillation.
Ronneburgite, K2MnV4O12, a new mineral from Ronneburg, Thuringia, Germany: Description and crystal structure
2001
Ronneburgite is a new chain vanadate mineral from Ronneburg, Thuringia, Germany. It occurs as reddish-brown crystals of equant, flattened, or short prismatic habit, up to 0.5 mm in length. The crystals have an adamantine luster and are translucent. Ronneburgite is biaxial negative with refractive indices n α = 1.925(5), n β = 1.960(10), n γ = 1.988(4), and 2 V x = 82°. Electron microprobe analysis (K 2 O = 16.93, MnO = 12.44, MgO = 0.62, V 2 O 5 = 68.54; total = 98.53 wt%) gives the empirical formula K 1.91 Mn 0.93 Mg 0.08 V 4.00 O 11.96 , which simplifies to K 2 MnV 4 O 12 . Ronneburgite is mono-clinic, space group P 2 1 / n , with a = 8.183(3), b = 9.247(3), c = 8.651(2) A, and β = 109.74…
Light Sensitive Lattice Defects In BaTiO 3 Containing Fe
1989
Electron spin resonance spectra, which can consistently be explained by the models Fe4+ - Vo and Fe5+ - vBa, have been observed with BaTiO3 containing Fe. Also Fe3+ and - Fe3+ - Vo have been identified. All these centers as well as several unidentified ones are observed to change their charge states under illumination. They thus are possibly in involved in photorefractive processes in BaTiO3 containing Fe.
Cylindrical Cuvette Light Refraction Measurements Technology to Analyse Biomedical Liquids
2015
Compact device of high sensitivity for measurement of the refractive indices for both stationary and flowing liquids has been developed. This device can be used to analyse a variety of biomedical liquids: urine, serum protein. The refractive index (RI) is determined by measuring the deviation of a laser beam passing through a cylindrical cuvette containing the test liquid. In order to significantly improve the resolution and stability of RI measurements, the repeated reflections and refractions of the light beam travelling through the cylindrical cuvette are employed.
Cylindrical optical microcavities: Basic properties and sensor applications
2011
Abstract A detailed theoretical analysis of the basic properties of whispering-gallery modes (WGM) of thin capillaries is presented. The sensitivity of the resonances, as well as the Q factor is analyzed as a function of the structural parameters of the capillary and the refractive index inside the capillary. A practical application where thin capillaries are used for the measurement of glucose concentration in water is presented as a chemical sensor demonstrator. A best sensitivity of 1.24 nm/% of glucose concentration in water is reported, which corresponds to more than 850 nm/RIU. Additionally, different experimental approaches are discussed to improve the sensitivity and the detection l…
Experimental Investigation of Fused Biconical Fiber Couplers for Measuring Refractive Index Changes in Aqueous Solutions
2016
A detailed experimental study of a simple and compact fiber optic sensor based on a fused biconical fiber coupler is presented, in which the sensitivity is improved by operating the coupler beyond the first coupling cycle. The sensor is demonstrated to perform high sensitivity measurements of refractive index changes by means of variation of sugar concentration in water. The device is operated to achieve a linear transmission response, allowing a linear relation between the sugar concentration and the output signal. The initial sensitivity was measured as 0.03 units of normalized transmission per unit of sugar concentration (g/100 mL), with a noise detection limit of a sugar concentration o…
Axial Length and Anterior Segment Alterations in Former Preterm Infants and Full-Term Neonates Analyzed With Scheimpflug Imaging.
2017
Purpose To compare the axial length and anterior segment alterations in preterm infants with and without retinopathy of prematurity with those of full-term infants. Methods The Wiesbaden Prematurity Study investigated 503 participants of former gestational age ≤32 weeks and gestational age ≥37 weeks now being aged 4 to 10 years. This study included 485 participants in the prospective controlled cross-sectional, hospital-based study with successful Pentacam Scheimpflug imaging. Anterior segment parameters, axial length measurements, and associated factors were analyzed. Results Corneal thickness did not differ between former preterm and full-term infants. Significant differences were found b…
<title>Holographic recording in amorphous semiconductor films</title>
1997
The present state of the real time holographic recording in amorphous semiconductor films is reviewed including mechanisms, parameters, properties and applications. Effects of the coherent, incoherent and relaxational self- enhancement as well as the influence of the film structure relaxation are considered. Quasi-permanent sub-band-gap light holographic recording is reported for the first time. 157
<title>Hologram recording in azobenzene oligomers</title>
2003
Elementary hologram (holographic grating) recording and their coherent optical erasure have been experimentally studied in azobenzene oligomer (ABO) layers differing by their chemical composition, matrices and by the connection type of azobenzene chromophores to the matrix (dispersed or covalently bound). The best holographic parameters (7.9% diffraction efficiency and 86 J/cm2 specific recording energy) were achieved in the samples with covalent bonding to the matrix. Vector recording is also possible. Recording is unstable and reversible. The coherent optical erasure studies have shown its efficiency dependencies on the initial diffraction efficiency, erasing beam intensity and grating pe…