Thermally poled silica samples are structurally heterogeneous: Electron diffraction evidence of partial crystallization

Abstract

Large structural modifications in v-SiO 2 are found to be induced by ''thermal poling,'' a treatment which makes the glass act as a frequency doubler of an impinging infrared light. The electron diffraction patterns of poled silica plates reveal the presence of a large amount ͑of order 10%͒ of crystallites showing patterns consistent with partial crystallization of the glassy matrix into the cristobalite polymorph of silica.

Near-surface modification of the third-order nonlinear susceptibility in thermally poled Infrasil™ glasses

“…This value, close to the breakdown electric field, could induce ionization of the motionless negative charges at the origin of the NL layer, deformation of the Si-O-Si bonds, and partial atomic rearrangement of SiO 2 . [11][12][13] Observations of Si-O-Si angle and Si-O bond length modifications have been reported for example in the literature. 12 Recently, Kashyap has reported that the ͑3͒ susceptibility can be modified by a factor of 2 due to a modification of electronic clouds of bonds under the local electric field.…”

Order/Disorder Hybrid Structures in Photonic Glass Materials

“…Although ultraviolet (UV) [8] and thermal [9] poling have been reported to be one of the most efficient way to induce the second-order optical nonlinearity in SiO 2 -related glasses, fibers, and films, the poled glasses show a degradation of the induced nonlinearity even at room temperature, ∼280 days [10]. It has been reported on crystallization with nano-and/or micro-scale particles in these poled glasses [11,12], and become well-understanding of its important role for obtaining large and stable induced second-order optical nonlinearity in the glass.…”

Poled glasses and poled fibre devices

“…In 2001 Cabrillo et al 59) made an interesting observation of crystallisation in thermally poled silica. TEM images indicated the formation of α-cristobalite.…”

“…24b) shows they are ~17 nm. Considering Cabrillo's earlier results, 59) it was suggested that these etched voids were evidence of crystallisation: the voids were left when the crystals were preferentially etched away by HF acid. If this interpretation is correct, thermal poling had induced a ~660 nm thick layer, 5.7 μm from the anode, of nanocrystals, with a maximum size of ~20 nm.…”