Eu-doped ZnO–HfO₂hybrid nanocrystal-embedded low-loss glass-ceramic waveguides

Abstract

We report on the sol-gel fabrication, using a dip-coating technique, of low-loss Eu-doped 70SiO2 -[Formula: see text] HfO2-xZnO (x = 2, 5, 7 and 10 mol%) ternary glass-ceramic planar waveguides. Transmission electron microscopy and grazing incident x-ray diffraction experiments confirm the controlled growth of hybrid nanocrystals with an average size of 3 nm-25 nm, composed of ZnO encapsulated by a thin layer of nanocrystalline HfO2, with an increase of ZnO concentration from x = 2 mol% to 10 mol% in the SiO2-HfO2 composite matrix. The effect of crystallization on the local environment of Eu ions, doped in the ZnO-HfO2 hybrid nanocrystal-embedded glass-ceramic matrix, is studied using photoluminescence spectra, wherein an intense mixed-valence state (divalent as well as trivalent) emission of Eu ions is observed. The existence of Eu(2+) and Eu(3+) in the SiO2-HfO2-ZnO ternary matrix is confirmed by x-ray photoelectron spectroscopy. Importantly, the Eu[Formula: see text]-doped ternary waveguides exhibit low propagation losses (0.3 ± 0.2 dB cm(-1) at 632.8 nm) and optical transparency in the visible region of the electromagnetic spectrum, which makes ZnO-HfO2 nanocrystal-embedded SiO2-HfO2-ZnO waveguides a viable candidate for the development of on-chip, active, integrated optical devices.

Fast, Low-Cost Synthesis of ZnO:Eu Nanosponges and the Nature of Ln Doping in ZnO

“…These molecules are volatile and seen as a white smoke during the fast decomposition, and they may be readsorbed on the sponge surface if the gas flow is not high enough or the powder bed is too thick to transport these product molecules away. No peak was found around 407 eV, where the N 1s peak of N 5+ in nitrate is expected, which shows that no nitrate remained after the fast reaction. , The amount of carbon and nitrogen was low, while the amount of oxygen per metal (Table ) was much higher than that in the samples made at higher temperatures. This fits the IR and TG data, which showed that there were a few percent of residues, probably mainly as carboxylates, such as unreacted OAc groups left at 200 °C, which increases the oxygen to metal content.…”

“…No peak was found around 407 eV, where the N 1s peak of N 5+ in nitrate is expected, which shows that no nitrate remained after the fast reaction. 130,131 The amount of carbon and nitrogen was low, while the amount of oxygen per metal (Table 1) was much higher than that in the samples made at higher temperatures. This fits the IR and TG data, which showed that there were a few percent of residues, probably mainly as carboxylates, such as unreacted OAc groups left at 200 °C, which increases the oxygen to metal content.…”

Lanthanide‐Based Luminescent Materials for Waveguide and Lasing

“…Shivakiran et al demonstratedp lanar waveguidesf rom Eu-doped SiO 2 -HfO 2 -ZnO ternary glass-ceramics. [18] Chen and Yins uccessfully precipitated sodium lanthanide fluorides NaLnF 4 (Ln = La-Lu) with cubic and hexagonal phase in aluminosilicate glass and demonstrate random upconversion lasing in the Yb/Er:b-NaYF 4 embedded glass-ceramics. [19] In 2016, Xu and Yu et al realized high-performancea nd compact self-cooling lasers for high temperature operation by using Ba 2 LaF 7 :Yb/ Er embedded glass-ceramics ( Figure 3).…”

“…Shivakiran et al. demonstrated planar waveguides from Eu‐doped SiO 2 ‐HfO 2 ‐ZnO ternary glass‐ceramics . Chen and Yin successfully precipitated sodium lanthanide fluorides NaLnF 4 (Ln=La‐Lu) with cubic and hexagonal phase in aluminosilicate glass and demonstrate random upconversion lasing in the Yb/Er:β‐NaYF 4 embedded glass‐ceramics .…”

Effect of structural evolution of ZnO/HfO2nanocrystals on Eu2+/Eu3+emission in glass-ceramic waveguides for photonic applications

“…Silica-hafnia glass waveguides prepared by sol-gel method are reported as low-loss waveguides and it transforms into glass-ceramic waveguides due to the formation of HfO 2 nanocrystals within the glass matrix after performing an additional heat-treatment at 1000 • C [13,14]. On the other hand, SiO 2 -ZnO composite glass-ceramic waveguides [15] also attract attention for photonic applications due to high nonlinear optical properties of ZnO and also due to the attractive properties of ZnO as a direct band gap semiconductor having wide band gap of ∼3.37 eV as well as large exciton binding energy of 60 meV at room temperature [16][17][18].…”