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The technique for the writing of crystal lines in glass by Nd:YAG laser irradiation, selective atom heat processing, is applied to rare-earth (Sm3+, Dy3+) barium borate glasses, and nonlinear optical β-BaB2O4 (β-BBO) crystal lines with a width of ∼5 μm are fabricated. The crystal lines show uniform colors in polarized optical microscope and second-harmonic generation (SHG) measurements. The azimuthal dependence of SHG signals in the crystal lines is the same as that in commercially available β-BBO bulk single crystals. It is demonstrated that the crystal lines written by YAG laser irradiations are β-BBO single crystals with the c-axis orientation along the laser scanning direction.

A series of transition and post-transition metal ion (Mn, Cu, Zn, Pb, Bi) binary borate glasses was studied with special consideration of the cations impact on the borate structure, the cations cross-linking capacity, and more generally, structure-property correlations. Infrared (IR) and Raman spectroscopies were used for the structural characterization. These complementary techniques are sensitive to the short-range order as in the differentiation of tetrahedral and trigonal borate units or regarding the number of non-bridging oxygen ions per unit. Moreover, vibrational spectroscopy is also sensitive to the intermediate-range order and to the presence of superstructural units, such as rings and chains, or the combination of rings. In order to clarify band assignments for the various borate entities, examples are given from pure vitreous BO to meta-, pyro-, ortho-, and even overmodified borate glass compositions. For binary metaborate glasses, the impact of the modifier cation on the borate speciation is shown. High field strength cations such as Zn enhance the disproportionation of metaborate to polyborate and pyroborate units. Pb and Bi induce cluster formation, resulting in PbO- and BiO-pseudophases. Both lead and bismuth borate glasses show also a tendency to stabilize very large superstructural units in the form of diborate polyanions. Far-IR spectra reflect on the bonding states of modifier cations in glasses. The frequency of the measured cation-site vibration band was used to obtain the average force constant for the metal-oxygen bonding, F. A linear correlation between glass transition temperature (T) and F was shown for the metaborate glass series. The mechanical properties of the glasses also correlate with the force constant F, though for cations of similar force constant the fraction of tetrahedral borate units (N) strongly affects the thermal and mechanical properties. For paramagnetic Cu- and Mn-borate glasses, N was determined from the IR spectra after deducing the relative absorption coefficient of boron tetrahedral versus boron trigonal units, α = α/α, using NMR literature data of the diamagnetic glasses.

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