The thermal properties of homogeneous and composite materials

A programme of work was instigated to investigate and improve the efficiency, and stability of intra-cavity étalons for the Argon ion laser, especially in the far blue to near ultra-violet wavelength region, by using sol–gel prepared silica. The original program has been modified by experiences outlined below. We have attempted to differentiate between the sol–gel derived and the high temperature prepared silica. We confirm that relatively small changes in thickness of silica monoliths can give rise to proportionally much larger changes of refractive index. Our main target has been to assess whether it is possible to make a new optical material that shows insignificant changes in optical path length or refractive index with temperature. [Continues.]