Amorphous nanostructuring in potassium niobium silicate glasses by SANS and SHG: a new mechanism for second-order optical non-linearity of glasses

Nanostructuring in glasses with composition close to KTiOPO4

“…This result with the correspondent XRD pattern showing the higher peak of the UTP phase on the amorphous background indicate that at this temperature two overlapped processes occur in the amorphous phase: the growth of the nanoinhomogeneities size and the start of the crystallization. Increasing the temperature of the heat treatment the I 2x value decreases and it becomes zero in the sample heated at 800°C for 1 h. This trend is very similar to that found in potassium niobium silicate glasses [8]. This unusual behavior has been mainly related to the local field gradients near the compositional inhomogeneities with varying dielectric constant e. An important contribute to second harmonic generation arise if significant fluctuations of the refractive index n 2 = e take place on very short distances (De/Dx where Dx indicates the periodicity of the inhomogeneities distribution) [8].…”

“…In our previous paper it was shown that in NGs nonlinear optical activity can arise from the growth in the glassy matrix of amorphous nanoinhomogeneities [8].…”

Nanosized structural transformation and nonlinear optical properties of lithium niobium germanate glasses

“…4, 5 and 7 allow to suppose that the same processes flow in LNG glasses during heat treatments at temperature near T g . Since LiNbO 3 phase precipitates finally during heat treatment both in LNG and LNS systems, suggestion about polarity of amorphous inhomogeneities in glasses characterized with fully amorphous XRD pattern, looks quite probable especially because amorphous inhomogeneities in Li 2 ONb 2 O 3 -ZnO-SiO 2 glasses, from which non-polar phase LiZnNbO 4 crystallize first, demonstrate, according to [5], negligible SHG efficiency originating by mechanism proposed by authors of [1]. Since LNG1 and LNG2 glasses were obtained and heattreated under the same conditions, the differences in the SHG values, glass crystallization and texturing behavior are assigned to the addition of alumina to LNG2 glass.…”

“…This weak point can be circumvented by several approaches. One of them is formation of nano-or microheterogeneities in glasses by amorphous phase separation and/or precipitation of nonlinear optical (NLO) crystals in glass matrix [1][2][3][4][5]. Among such crystals LiNbO 3 can be marked for its ferroelectric, electro-optical, piezoelectric and photorefractive properties [6][7][8] and ability to precipitate easily from glass [9][10][11][12].…”

Toward an ideal nanomaterial for on-chip Raman laser

“…The process, involving two partially overlapped processes, namely, phase separation and crystallization, produces a transparent material. [52][53][54] In order to obtain transparent nanostructured glasses, it is necessary that amorphous or crystalline phase grows from the glass exclusively with a bulk nucleation mechanism. By means of a proper nucleation heat treatment, it is possible to produce a high number of bulk nuclei and, consequently, a high number of nanocrystals small enough to avoid any light scattering.…”