Infrared and laser spectroscopic characterization of aluminium defects in cultured quartz

Optical absorption at He-Ne and argon laser frequencies has been used to map the distribution of aluminium-hole centres, Al-H(+), in irradiated and vacuum swept quartz. The absorption band associated with Al-h(+) has a strong peak centered at 435 nm and a weaker one at 633 nm. Argon laser lines at 488 and 514.5 nm are close to the wavelength of the stronger peak, while the He-Ne line at 632.8 nm is nearly coincident with that of the weaker peak. Large variations in Al-h(+) absorption for irradiated and vacuum swept crystals correspond to visually observed changes in coloration. The laser method is sensitive and nondestructive, and gives a quantitative measurement adaptable to computerized scanning and recording of data. Measurements of both Al-h(+) and infrared-active aluminium hydroxide centres, Al-OH(-), are used to evaluate the distribution of aluminium-associated defect centres and determine aluminium variations over an entire crystal.