Highly photorefractive Eu³⁺activated sol-gel SiO 2 -SnO 2 thin film waveguides

Abstract

We report on the photorefractive properties of tin-silica slab waveguides, deposited on vitreous-SiO 2 by means of sol-gel dip-coating technique. The basic composition of these amorphous binary systems is 75 SiO 2 -25 SnO 2 mol% with 1 mol% of Eu 3+ ions. Europium was chosen as an optical probe of the glass structure. These guiding structures exhibit low propagation losses (around 0.5 dB/cm at 633 nm) and a high refractive index modulation, as large as -1.5 × 10 − 3 under the UV irradiation of a KrF excimer laser source at λ = 248 nm, suitable for writing waveguide gratings.

Glass‐Ceramic Materials for Guided‐Wave Optics

“…In fact, the embedded rare earth‐doped nanocrystals with low cut‐off vibrational energy, such as hafnia, fluoride, titania, tin oxide, and zirconia, reduce the nonradiative contribution to the relaxation mechanism, allowing high fluorescence efficiency. Finally, some kinds of nanocrystals such as SnO 2 have been demonstrated to be excellent rare earth sensitizers, and performing SiO 2 –SnO 2 waveguides have been demonstrated . Tin silicate films, by the way, are of interest because they are photosensitive too, and waveguides may be written by direct UV exposure .…”

Photonic glass ceramics based on SnO2 nanocrystals: advances and perspectives

“…The role of SnO 2 nanocrystals as rare-earth ion luminescence sensitizers allows to overcome the low absorption cross section of the Er 3+ ion 7,8 . The photorefractivity of sol-gel derived SnO 2 glass-ceramics allows applying the robust direct laser photoinscription technique on the systems to fabricate Bragg gratings and channel waveguides for waveguide integrated laser 9,10,11 . The results presented in this communication not only demonstrate the viability and outstanding properties of the SiO 2 -SnO 2 glass-ceramics for photonic applications but also put the basis for the fabrication of solid state and integrated lasers.…”

Red photonic glasses and confined structures

“…In fact, the embedded rare-earth-doped nanocrystals with low cutoff vibrational energy, such as hafnia, fluoride, titania, tin oxide, and zirconia, reduce the nonradiative contribution to the relaxation mechanism, allowing high fluorescence efficiency. Finally, some kind of nanocrystals such as SnO 2 have demonstrated to be excellent rare earth sensitizers and excellent SiO 2 -SnO 2 waveguides have been demonstrated [12][13][14]. We want close this section about glass-ceramics pointing out the advantage of this system for energy transfer optimization.…”

“…Concerning the role of nanocrystals as rare earth sensitizers, SnO 2 nanocrystals constitutes a textbook example [12][13][14]. SnO 2 is a wide band-gap (E g = 3.6 eV at 300 K) n-type semiconductor and exhibits a maximum phonon energy of about 630 cm −1 .…”

“…A number of solutions has been studied in order to permit the increase of the total absorption cross section of the whole system, with the aim to enhance the spectroscopic properties of erbium ions at 1.5 µm. Under this perspective several kinds of rare earth sensitizers including semiconductor nanocrystals [12][13][14] and metallic nanoparticles [15] A lot of research groups have focused their attention in the preparation of erbium doped glasses codoped with different kind of rare earth ions. It has been shown, that the introduction of ytterbium ions enhances the system absorption at 980 nm, making the pumping mechanism more efficient [11,[16][17][18].…”