Laser patterning of oriented LiNbO₃ crystal particle arrays in NiO‐doped lithium niobium silicate glasses

Abstract

The patterning of LiNbO3 crystals was carried out at the surface of NiO‐doped 40Li2O‐32Nb2O5‐28SiO2 (LNS) glasses using continuous‐wave Yb:YVO4 fiber laser (wavelength: 1080 nm) to gain a deeper understanding of the crystal growth in the laser‐induced crystallization in glasses. It was suggested that in the conventional crystallization in an electric furnace, NiO acts as a nucleation agent in the LNS glass and the addition of NiO suppresses the c‐axis orientation of LiNbO3 at the glass surface. It was found from birefringence image observations that LiNbO3 crystals with a dot shape have a radial orientation from the center to the edge parts. Highly c‐axis oriented LiNbO3 crystal particle (diameter: 7‐11 μm) arrays were patterned along the laser scanning direction in laser irradiations (scanning mode: eg, the laser power of 1.60 W and scanning speeds of 7‐10 μm/s) in 3 mol% NiO‐doped LNS glass. It was suggested that the nucleation and crystal growth of LiNbO3 crystals are taking place repeatedly (periodically) along the laser scanning direction, consequently providing LiNbO3 crystal particle arrays.

Features of electronic polarizability and approach to unique properties in tellurite glasses

“…However, it is possible to break inversion symmetry in a microscopic scale through techniques such as thermal/electrical poling and to induce second‐order optical nonlinearity . Crystallization of glasses, that is, the formation of non‐linear optical crystals, is also another effective method for inducing SHGs . Narazaki et al examined the effect of thermal poling on the second harmonic (SH) intensity of Na 2 O‐ZnO‐TeO 2 glasses and proposed that the large electric field in the anode‐side glass surface region leads to an orientation of asymmetric tellurite structural units of TeO 4 tbp and TeO 3 tp having electric dipoles.…”

“…[107][108][109] Crystallization of glasses, that is, the formation of non-linear optical crystals, is also another effective method for inducing SHGs. 43,[110][111][112] Narazaki et al 107 examined the effect of thermal poling on the second harmonic (SH) intensity of Na 2 O-ZnO-TeO 2 glasses and proposed that the large electric field in the anode-side glass surface region leads to an orientation of asymmetric tellurite structural units of TeO 4 tbp and TeO 3 tp having electric dipoles. Tamagawa et al 109 applied a thermal poling (2.0 kV (DC voltage), 210°C, 40 min) to transparent glass-ceramics of 15K 2 O-15Nb 2 O 5 -68TeO 2 -2MoO 3 and found that the SH intensity of nanocrystallized glasses is enhanced, suggesting the increase in polarization in nanocrystals.…”

Stress‐induced crystal axis spiral rotation in multiferroic β'‐Gd2(MoO4)3 observed only in glass crystallization

“…Usually, glass‐ceramics are fabricated using heat‐treatment in an electric furnace, in which glasses are heated uniformly over the whole part of a given glass. Recently, laser‐induced crystallization has received much attention, in which single crystals and nanocrystals are patterned freely in spatially selected parts in glasses, being a completely different approach to the glass‐crystallization compared with a usual crystallization technique in an electric furnace 12,20‐26 . Among glass‐ceramics reported so far, an extremely unique and curious phenomenon has been observed in the crystallization of multiferroic (ferroelectric and ferroelastic) β'‐Gd 2 (MoO 4 ) 3 (designated here as β’‐GMO) in Gd 2 O 3 ‐MoO 3 ‐B 2 O 3 glasses (GdMoBO glasses) 27‐34 .…”

“…Recently, laser-induced crystallization has received much attention, in which single crystals and nanocrystals are patterned freely in spatially selected parts in glasses, being a completely different approach to the glass-crystallization compared with a usual crystallization technique in an electric furnace. 12,[20][21][22][23][24][25][26] Among glass-ceramics reported so far, an extremely unique and curious phenomenon has been observed in the crystallization of multiferroic (ferroelectric and ferroelastic) β'-Gd 2 (MoO 4 ) 3 (designated here as β'-GMO) in Gd 2 O 3 -MoO 3 -B 2 O 3 glasses (GdMoBO glasses). [27][28][29][30][31][32][33][34] That is, crystals formed in the crystallization break into small pieces spontaneously during the crystallization in the inside of an electric furnace, not during the cooling in air after the crystallization.…”

Thermodiffusion of alkali ions in alkali niobophosphate glasses

“…The study of thermodiffusion processes in solid ionic electrolytes provides the fundamental basis for creating gradient structures inside glass samples through local changes in the chemical composition by femtosecond laser radiation, 1–5 continuous wave (CW) laser, 6–8 by means of thermal poling, 9–11 and thermally activated ion‐exchange 12,13 …”