Determination of Refractive Indices and Linear Coefficients of Thermal Expansion for Development of Athermal Glass

2011 ◽  
Vol 675-677 ◽  
pp. 1113-1116
Author(s):  
Yoshinao Kobayashi ◽  
Taiichi Shimizu ◽  
Rie Endo ◽  
Masahiro Susa
Keyword(s):  
Refractive Index ◽  
Thermal Expansion ◽  
Temperature Dependence ◽  
Path Length ◽  
Sessile Drop ◽  
Coefficient Of Thermal Expansion ◽  
Optical Path Length ◽  
Optical Path ◽  
Linear Coefficient ◽  
Optical Fibre Transmission

Recently, there has been a growing importance of development of ‘athermal glass’ having no temperature dependence in its optical path length and is expected to be used in optical devices for the optical fibre transmission system. The athermal characteristic is usually evaluated by temperature dependence of optical path length, (1/l)･(dS/dT) ( l : geometrical length, S : optical path length, T : temperature), which is the summation of nα and dn/dT (n: refractive index, α: linear coefficient of thermal expansion). In the present work, the refractive index and liner coefficient of thermal expansion have been determined for silicate glasses containing titanium oxides in the temperature range from room temperature to about 673 K, using ellipsometry and utilizing the sessile drop method. The values of nα and temperature coefficient of n ranged from 1.289×10-5 K-1 to 3.345×10-5 K-1 and from 0.270×10-5 K-1 to 1.467×10-5 K-1, respectively, depending on the glass composition. Consequently, only 80SiO2-5TiO2-15Na2O glass has shown almost the same degree of athermal characteristic as SiO2 glass, having more advantages in practice due to its lower melting temperature than SiO2.

Study of temperature dependence of the optical path length in ion doped solids

2003 ◽  
Author(s):  
A. A. Andrade ◽  
Tomaz Catunda ◽  
J. Mura ◽  
Mauro L. Baesso
Keyword(s):  
Temperature Dependence ◽  
Path Length ◽  
Optical Path Length ◽  
Optical Path

scholarly journals Interferometric imaging of thermal expansion for temperature control in retinal laser therapy

2021 ◽  
Author(s):  
David Veysset ◽  
Tong Ling ◽  
Yueming Zhuo ◽  
Daniel Palanker
Keyword(s):  
Thermal Expansion ◽  
Laser Therapy ◽  
Temperature Rise ◽  
Path Length ◽  
Optical Path Length ◽  
Optical Path ◽  
Laser Exposure ◽  
Interferometric Imaging ◽  
Tissue Phantom ◽  
Length Changes

Precise control of the temperature rise is a prerequisite for proper photothermal therapy. In retinal laser therapy, the heat deposition is primarily governed by the melanin concentration, which can significantly vary across the retina and from patient to patient. In this work, we present a method for determining the optical and thermal properties of layered materials, directly applicable to the retina, using low-energy laser heating and phase-resolved optical coherence tomography (pOCT). The method is demonstrated on a polymer-based tissue phantom heated with a laser pulse focused onto an absorbing layer buried below the phantom's surface. Using a line-scan spectral-domain pOCT, optical path length changes induced by the thermal expansion were extracted from sequential B-scans. The material properties were then determined by matching the optical path length changes to a thermo-mechanical model developed for fast computation. This method determined the absorption coefficient with a precision of 2.5% and the temperature rise with a precision of about 0.2°C from a single laser exposure, while the peak did not exceed 8°C during 1 ms pulse, which is well within the tissue safety range and significantly more precise than other methods.

Measurement of Curative Diffusion Between Rubbers by Microinterferometry

1969 ◽  
Vol 42 (4) ◽  
pp. 1058-1078 ◽  
Author(s):  
J. Brooke Gardiner
Keyword(s):  
Refractive Index ◽  
Diffusion Coefficients ◽  
Path Length ◽  
Optical Path Length ◽  
Considerable Change ◽  
Optical Path ◽  
Reference Area ◽  
Differential Diffusion ◽  
Concentration Diffusion ◽  
And Diffusion

Abstract Diffusion of sulfur and MBTS across interfaces between dissimilar rubbers has been measured by microinterferometry. This technique involves the comparison of optical path length through refractive index gradients, due to diffusion, against that of a reference area. Differential diffusion coefficients are obtained showing considerable change in coefficient with curative concentration. Diffusion of sulfur between NR, SBR, and BR is quite similar to diffusion in the homo-polymer. Butyl rubber has a much lower diffusivity and limits diffusion of a curative from another rubber. The method also can be used for dissolution measurements on curatives. Microinterferometry is particularly useful in obtaining concentration and diffusion data at short distances from an interface.

Investigation of particulate systems using optical pathlength spectroscopy

2000 ◽  
Vol 627 ◽  
Author(s):  
Gabriel Popescu ◽  
Aristide Dogariu
Keyword(s):  
Path Length ◽  
Random Media ◽  
Michelson Interferometer ◽  
Industrial Process ◽  
Optical Path Length ◽  
Industrial Applications ◽  
Optical Path ◽  
Interference Signal ◽  
Optical Length ◽  
Reference Mirror

ABSTRACTIn many industrial applications involving granular media, knowledge about the structural transformations suffered during the industrial process is desirable. Optical techniques are noninvasive, fast, and versatile tools for monitoring such transformations. We have recently introduced optical path-length spectroscopy as a new technique for random media investigation. The principle of the method is to use a partially coherent source in a Michelson interferometer, where the fields from a reference mirror and the sample are combined to obtain an interference signal. When the system under investigation is a multiple-scattering medium, by tuning the optical length of the reference arm, the optical path-length probability density of light backscattered from the sample is obtained. This distribution carries information about the structural details of the medium. In the present paper, we apply the technique of optical path-length spectroscopy to investigate inhomogeneous distributions of particulate dielectrics such as ceramics and powders. The experiments are performed on suspensions of systems with different solid loads, as well as on powders and suspensions of particles with different sizes. We show that the methodology is highly sensitive to changes in volume concentration and particle size and, therefore, it can be successfully used for real-time monitoring. In addition, the technique is fiber optic-based and has all the advantages associated with the inherent versatility.

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