Micro-Raman spectroscopy: a technique for analyzing bubbles in glass.

Micro-Raman spectroscopy is shown to be a nondestructive technique suitable for analyzing bubbles in glass. Using a 90° scattering geometry it is possible to identify various gases in bubbles entrapped in different glass samples. A very accurate optical alignment is possible by calculating focus size, focus position, and the volume from which the scattered light is collected. In this way bubbles with diameters down to 35 μm can be measured. In addition to the rotational spectra even the much weaker vibrational spectra, which are easier to analyze, can be measured.