Laser Mapping of Al-h+ Impurity Distribution in Vacuum Swept Crystalline Quartz

We have used HeNe laser light absorption to perform 2-D spatial mapping of hole-compensated aluminum (Al-h+) impurity sites produced during vacuum sweeping of crystalline quartz. Application of an electric field parallel to the optic axis can produce a hole(1) trapped at a non-bonding oxygen ion (AlO4)° site. These hole-compensated Al-h+ sites introduce color center absorption. The electro-diffusion process (sweeping) is performed under elevated temperature and vacuum conditions. The diffusion process produces a time-dependent spatial distribution of the Al-h+ centers and associated A1-band optical absorption which is coincident with the 633-nm-HeNe laser wavelength. Spatial variations in the A1-band absorption for swept quartz and for quartz subjected to ionizing radiation are correlated with the observed(1) coloration. Devices fabricated from crystalline quartz with hole-compensated aluminum impurity sites are resistant to the effects of ionizing radiation. The 2-D mapping of optical absorption is compared to electron spin resonance (ESR) measurements of aluminum impurity concentration in samples of vacuum swept cultured quartz.