Measurement of refractive index change with temperature using thermal self-phase modulation

The thermal self-phase modulation effect, arising when a laser beam passes through absorbing materials, is used to measure the product of absorption coefficient and dn/dT (change of refractive index with temperature). By adding a dye so that absorption coefficient is readily measured, the value of dn/dT may be found. The advantages and disadvantages of the method are discussed, with results for several liquids given and experiments on the effects of the added dye.