Refractive index change with temperature

The refractive index changes with temperature. If your reading is not the same as that of a handbook, check the temperatures before you despair. 

Temperature Sensing. As shown in Fig. 16, a layer of silicon (whose refractive index changes with temperature) is placed in the optical path in place of the evacuated cavity, as previously described. The second reflector (glass) is rigid. The effective path length thus changes with temperature. 

Also referred to as cold checking. Temperature coefficient of refractive index n. The change in refractive index (n) with temperature. The degree of variation of n... 

Temperature Coefficient of Refractive Index n The change in refractive index (n) with temperature. The degree of variation of n depends on the composition of the substance and the state of aggregation, e.g., whether it is a soKd or a liquid. It is usually about 100 X larger for Uquids than for solids and about —0.0005/°C for Kquids. 

Both kinetic and thermodynamic approaches have been used to measure and explain the abrupt change in properties as a polymer changes from a glassy to a leathery state. These involve the coefficient of expansion, the compressibility, the index of refraction, and the specific heat values. In the thermodynamic approach used by Gibbs and DiMarzio, the process is considered to be related to conformational entropy changes with temperature and is related to a second-order transition. There is also an abrupt change from the solid crystalline to the liquid state at the first-order transition or melting point Tm. 

One other experimental observation demonstrates the difference between old and new technologies. When a composition such as treated fumed silica In polymer B Is heated, haze develops. This haze Is due to the fact that the refractive Index of the polymer changes with temperature quite drastically while that for the solid filler does not. To demonstrate the change In refractive Index with temperature, the refractive Index, of j catalyst free devolatilized polymer A sample gave the following data ... 

Variation of refractive index of the MNA solution in various solvents at 20 C as a function of concentration was obtained using an Abbe refractometer. Refractive indices available,as shown in Figure 5, range from 1.4 to 1.5 with the solvents used, from which one can easily match the refractive index of silica optical fibers. Temperature dependence of refractive index in MNA saturated solutions,measured at 15 C and 250C,is tabulated in Table 2. Fluctuation of refractive index,as a result of the temperature variation, turned out to be approximately 0.0004/ 0, so that It is essential to control the solution temperature to better than 0.1 in this experiment,in order for only electronic nonlinear refractive index change to be effective. 

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