Measurement of the differential thermal expansion and temperature dependence of refractive index in gradient-index glass

1985 ◽  
Vol 24 (24) ◽  
pp. 4334 ◽  
Author(s):  
Paul O. McLaughlin ◽  
Duncan T. Moore
Keyword(s):  
Refractive Index ◽  
Thermal Expansion ◽  
Temperature Dependence ◽  
Gradient Index ◽  
Differential Thermal Expansion

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.

A neutron powder diffraction determination of the thermal expansion tensor of crocoite (PbCrO4) between 60 K and 290 K

1996 ◽  
Vol 60 (403) ◽  
pp. 963-972 ◽  
Author(s):  
Kevin S. Knight
Keyword(s):  
Thermal Expansion ◽  
Temperature Dependence ◽  
Powder Diffraction ◽  
Maximum Expansion ◽  
Lattice Constants ◽  
Thermal Expansion Tensor ◽  
Diffraction Determination ◽  
Line Passing ◽  
Neutron Time

AbstractThe thermal expansion tensor of crocoite has been determined from high-resolution neutron time-of-flight powder diffraction data. The temperature dependence of the lattice constants between 4.5 K and 290 K have been fitted to a quasi-harmonic Einstein model, and the temperature dependence of the thermal expansion tensor has been calculated for 60 K ≤ T ≤ 290 K. The magnitudes of the principal expansivities and their orientation exhibit saturation behaviour for temperatures above 300 K. The predicted saturated expansion coefficients are α11 = 33.1(1) × 10−6K−1, α22 = 15.72(3) × 10−6K−1, α33 = 3.36(1) × 10−6K−1, with α22 parallel to b and α11 lying at an angle of −37.86(5)° to c for the P21/n setting of the crystal structure. The direction of maximum expansion is approximately parallel to both and the least-squares line passing through the projection of the chromium atoms on (010). The direction of minimum expansion lies approximately parallel to [101]. No evidence was found for either a structural or magnetic phase transition between 4.5 K and 300 K.

Phonon Decay in GaN and AlN and Self-Heating in III-N Devices

2006 ◽  
Vol 955 ◽  
Author(s):  
Mark Holtz ◽  
D. Y. Song ◽  
S. A. Nikishin ◽  
V. Soukhoveev ◽  
A. Usikov ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Temperature Dependence ◽  
High Quality ◽  
Self Heating ◽  
Phonon Emission ◽  
Decay Properties ◽  
Phonon Properties

ABSTRACTWe report studies of the temperature dependence of Raman lines in high quality GaN and AlN. The temperature dependence of the phonon energies and linewidths are used to produce consistent phonon decay properties of zone center optic phonons. In GaN we observe the E22 phonon to decay into three phonons, while the A1(LO) phonon is well described according to the so-called Ridley process – one TO and one LA phonon. For AlN the E22 phonon decays by two phonon emission and the A1(LO) line also exhibits a dependence consistent with the Ridley process. Along with the phonon decay processes, it is important in each case to take into account the contribution of the thermal expansion, including the temperature dependence, to describe observed temperature shifts in the phonon properties.

The direct determination of the temperature dependence of the refractive index of liquids and solids

1976 ◽  
Vol 9 (14) ◽  
pp. 1945-1951 ◽  
Author(s):  
G Abbate ◽  
A Attanasio ◽  
U Bernini ◽  
E Ragozzino ◽  
F Somma
Keyword(s):  
Refractive Index ◽  
Temperature Dependence ◽  
Direct Determination
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