Patterning of Non‐Linear Optical Crystals in Glass by Laser‐Induced Crystallization

Abstract

This paper reports recent progress in the patterning of non-linear optical crystals on the glass surface by laser irradiation. Two techniques for the writing of crystal lines have been developed, i.e., rare-earth (samarium) atom heat processing and transition metal atom heat processing, in which a continuous wave Nd:YAG laser (wavelength: k 5 1064 nm) is irradiated to the glasses containing rare-earth (RE: Sm 31 , Dy 31 ) ions or transition metal (TM: Ni 21 , Fe 21 , V 41 ) ions. The writing of crystal lines such as b-BaB 2 O 4 , Sm x Bi 1Àx BO 3 , and Ba 2 TiGe 2 O 8 showing second harmonic generations has been successful. It is clarified from the azimuthal dependence of second harmonic intensity and polarized micro-Raman scattering spectra that crystal lines consist of highly oriented crystals along the crystal line growth direction. It is also possible to write two-dimensional crystal bending or curved lines by just changing the laser scanning direction. The mechanism of the laser-induced crystallization has been proposed. II. REAH/TMAH ProcessingIn rare-earth atom heat processing, cw Nd:YAG lasers with l 5 1064 nm are irradiated onto glasses containing Sm 2 O 3 (or M. Davies-contributing editor

Micro-architecture of nonlinear optical Ba2TiGe2O8 crystal dots and lines on the surface of laser-induced crystallized glasses by chemical etching

“…Recently, crystal dots and lines consisting of nonlinear optical crystals such as b-BaB 2 O 4 , Ba 2 TiGe 2 O 8 , and (Sr,Ba)Nb 2 O 6 have been patterned on the glass surface by irradiations of lasers such as continuous wave (cw) Nd:YAG lasers with a wavelength of l = 1064 nm [6][7][8][9][10][11][12][13]. In those laser-induced crystallization techniques, irradiated lasers are absorbed by rare-earth (RE) ions such as Sm 3+ through f-f transitions or transition metal (TM) ions such as Cu 2+ through d-d transitions in glasses, and the laser energy absorbed by RE or TM ions is transferred to lattice vibrations through a non-radiative relaxation process (electron-phonon couplings).…”

“…Thus, the surrounding of RE or TM ions is heated, and consequently crystallizations are induced. Crystal lines have been patterned by scanning lasers [6][7][8][9][10][11][12][13].…”

Characterization of BaTiO₃ crystals formed in aluminosilicate glasses and their laser patterning

“…This absorption coefficient would be enough to induce structural modifications in BTSA glass by Yb:YVO 4 lasers, 19)21), 35) although the fraction of nonradiative relaxation process for Cu 2+ ions in BTSA glass is unclear.…”

“…So far, ferroelectric crystals with high orientations such as LiNbO 3 , NaNbO 3 and ¢'-Gd 2 (MoO 4 ) 3 have been patterned successfully by designing glass composition and laser irradiation conditions. 19)23),27),36),37) For the laser patterning of homogeneous lines with tetragonal BaTiO 3 single crystals, further study, in particular on the glass system and composition, would be required.…”

The glass transition and crystallization kinetic studies on BaNaB9O15glasses

“…There are many advantages associated with glass-ceramics such as low/zero porosity and consequently high dielectric break down voltages, easy controllability of the properties and could be produced in a variety of sizes and shapes. Glassy dielectric materials comprising nano/micro crystallites of polar phases have been known to exhibit interesting physical properties which include piezoelectric, pyroelectric, electrooptic and non-linear optical [1,[4][5][6][7][8][9]. In the last two decades, researchers have investigated glass-ceramic systems containing ferroelectric crystalline phases such as; LiNbO 3 [8], SrBi 2 Nb 2 O 9 [4] Bi 2 WO 6 [5] etc.…”