Athermal phosphate glass matrix at room temperature investigated by thermal lens

The effects of substitution of Al2O3 by K2O in the raw materials for preparing phosphate glasses have been investigated using interferometer and thermal lens techniques. When the K2O content reaches similar to 9 wt%, both techniques present an athermal behavior, with a temperature coefficient of the optical path ds/dT equal to zero. From the interferometer measurements, a linear shift of the long period in the interference fringe from 77 K to room temperature was observed, whose athermal temperature is described by the linear function AT =145+246 center dot X. Furthermore, when applying thermal lens measurements at room temperature, it was found that there is a range of K2O concentration within the P2O5-Al2O3-Na2O-K2O glass system that becomes athermal. It was also observed that two glasses of the set exhibit athermality three times greater compared to the commercial athermal glass Q98, in terms of the parameter C-TL (proportional do ds/dT) obtained from the thermal Lens.