Local laser-induced crystallization of lanthanum boron germanate glass near LaBGeO5 composition

Local crystallization of glasses induced by laser irradiation is an efficient technique of fabricating regular structures (arrays of dots, lines, gratings) which can be used as waveguides and other elements in the novel glass-based devices of integrated optics and photonics. One of the most important cases is local laser-induced crystallization of nonlinear optical crystals which can form a base for integrated active elements for optical frequency conversion or electrooptical modulation. We report a comparative study on laser-induced crystallization of lanthanum borogermanate glasses with different additives using different types of lasers. A stillwellite-like crystalline LaBGeO5 phase possessing ferroelectric and nonlinear optical properties or its solid solutions with partial substitution of La by Nd or Sm depending on the additive are shown to precipitate as well-formed crystals a few microns in size near the glass surface under radiation of the continuous wave Nd:YAG laser (1064 nm), the continuous wave copper vapor laser (510,6 nm and 578,2 nm). To enhance optical absorption of the basic glass we added Sm2O3 oxide for irradiation at 1064 nm and Nd2O3 for irradiation at 510,6 nm and 578,2 nm whereas pure glass was subjected to KrF laser irradiation due to high native absorption at 248 nm. A copper vapor laser which almost has not been applied to this technique before is shown to be an effective tool for laser-induced crystallization providing short times of crystal growth and high speed of laser writing.