Progress of optical materials characterization with time [Invited]

Abstract

Modern glass producers like SCHOTT are producing and developing optical materials for various specialized applications in photonics and optical and microlithography technology. To achieve the specifications, huge efforts in metrology R&D activities have been made, and specialized tools have been developed and installed in the metrology labs over the last decades. The optical material quality requirements of such materials have been extremely high, and a continuous increase in activities has been necessary and is still required. Therefore further development and implementation of diagnostics have been performed, like optical spectroscopy and refractography, over the last decades. In the past and today, special diagnostics have been available to qualify materials for the absolute refractive index, transmission, radiation durability, and inner quality to ensure the quality of the produced materials. Methods used for this qualification are minimum deviation, precision spectral photometers, in-situ transmission measurements using UV lasers, and Rayleigh scattering. We present some past activities for metrology that have been necessary to visualize the status and the improvement of the optical quality with the help of new and continuously improved metrology.