Target dependent femtosecond laser plasma implantation dynamics in enabling silica for high density erbium doping

Abstract

Chemical dissimilarity of tellurium oxide with silica glass increases phase separation and crystallization tendency when mixed and melted for making a glass. We report a novel technique for incorporating an Er(3+)-doped tellurite glass composition into silica substrates through a femtosecond (fs) laser generated plasma assisted process. The engineered material consequently exhibits the spectroscopic properties of Er(3+)-ions, which are unachievable in pure silica and implies this as an ideal material for integrated photonics platforms. Formation of a well-defined metastable and homogeneous glass structure with Er(3+)-ions in a silica network, modified with tellurite has been characterized using high-resolution cross-sectional transmission electron microscopy (HRTEM). The chemical and structural analyses using HRTEM, Rutherford backscattering spectrometry (RBS) and laser excitation techniques, confirm that such fs-laser plasma implanted glasses may be engineered for significantly higher concentration of Er(3+)-ions without clustering, validated by the record high lifetime-density product 0.96 × 10(19) s.cm(-3). Characterization of planar optical layers and photoluminescence emission spectra were undertaken to determine their thickness, refractive indices and photoluminescence properties, as a function of Er(3+) concentration via different target glasses. The increased Er(3+) content in the target glass enhance the refractive index and photoluminescence intensity of the modified silica layer whilst the lifetime and thickness decrease.

Figure 1. Distinct images of the EDTS layer on silica;

(a) FIB-SEM image of the EDTS layer cross-section; (b) SAED pattern captured from the EDTS layer confirming the amorphous state; (c) HRTEM image of the interface between the EDTS layer and the silica substrate showing no clustering of Er³⁺-ions.

Figure 2. Typical RBS spectra of an EDTS layer on silica substrate measured at two different sample tilt angles of 7° (open dots) and 45° (solid dots), respectively.

The corresponding RBX simulations are also shown (red and blue lines). Surface spectrum edges for Er, Te, Zn, Si, Na, and O are indicated.

Figure 3. Erbium concentration in the EDTS layer vs. the corresponding erbium concentration in the initial tellurite target glass.

Figure 4. Thickness and refractive index trends for the EDTS layers with the Er³⁺-ion concentrations in the target glass.

Figure 5

Photoluminescence spectra of the ⁴I_13/2–⁴I_15/2 transition of Er³⁺-ions with varying doping concentration in (a) tellurite target glass and (b) EDTS layer on silica. (c) Measured lifetime of EDTS and erbium-doped tellurite target glass as a function of Er³⁺-ion concentrations.