TeO2-BaO-Bi2O3 tellurite optical glasses II. -- Linear and non-linear optical and magneto-optical properties

TL;DR

The paper characterizes linear, nonlinear, and magneto-optical properties of TeO2–BaO–Bi2O3 tellurite glasses across the full glass-forming region, using melt-quenching synthesis, spectroscopic ellipsometry, and Faraday rotation measurements. By applying a Tauc-Lorentz/Gaussian dispersion model and a Sellmeier description in the transparent region, it derives refractive indices (e.g., $n_{1550}=1.922$–$2.084$) and band gaps ($E_g\approx3.1$–$3.6$ eV), and quantifies non-linear refractive indices ($n_2\approx1.63\times10^{-11}$ to $3.45\times10^{-11}$ esu) alongside Verdet constants ($V_{632}\approx26.7$ to $45.3$ rad T$^{-1}$ m$^{-1}$). The magneto-optical anomaly parameter $\gamma\approx0.71$–$0.92$ is extracted from spectral fits, enabling reliable MO predictions, including $V_{1550}\approx4.2$–$6.7$ rad T$^{-1}$ m$^{-1}$ via Becquerel/Sellmeier models. A multilinear regression links $n_{1550}$ to molar/atomic oxide contents with $r\ge0.993$, confirming strong composition–optical-property correlations and reproducibility. Compared to TeO2–ZnO–BaO glasses, TeBaBi shows higher $n$, $n_2$, and MO response, underscoring its promise for dispersion-engineered photonic/MO devices across visible to mid-IR wavelengths.

Abstract

The present study investigates the linear and non-linear optical and magneto-optical properties of TeO$_2$-BaO-Bi$_2$O$_3$ (TeBaBi) glasses prepared by the conventional melt-quenching technique at 900 °C. Prepared glass composition ranges across the whole glass-forming-ability (GFA) region focusing on mutual substitution trends of constituent oxides, where TeO$_2$: 55-85 mol.%, BaO: 10-35 mol.%, Bi$_2$O$_3$: 5-15 mol.%. Studied glasses exhibit high values of linear ($n_{632} \approx$ 1.922-2.084) and non-linear refractive index ($n_2\approx$1.63-3.45$\times10^{-11}$ esu), Verdet constant ($V_{632} \approx$ 26.7-45.3 radT$^{-1}$m$^{-1}$) and optical band gap energy ($E_g \approx$ 3.1-3.6 eV). The introduction of TeO$_2$ and Bi$_2$O$_3$ results in increase of both linear/non-linear refractive index and Verdet constant, with a more pronounced influence of Bi$_2$O$_3$. Measured spectral dispersion of refractive index and Verdet constant were used for estimation of magneto-optic anomaly parameter ($γ\approx$ 0.71-0.92), which may be used for theoretical modelling of magneto-optic response in diamagnetic TeBaBi glasses. Additionally, the properties of the prepared TeBaBi glasses were directly compared to those of the TeO$_2$-ZnO-BaO glass system, which was prepared and characterized under similar experimental conditions. The compositional dependence of the refractive index in both glass systems was described using multilinear regression analysis, demonstrating high correlation and uniformity of estimation across the entire GFA region. This makes them highly promising for precise dispersion engineering and construction of optical devices operating from visible to mid-infrared spectral region.

Figures (5)

• Figure 1: TeO2$-$BaO$-$Bi2O3 (TeBaBi) ternary diagram with indicated glass compositions (black circle) and the boundary of glass-forming region (dashed)HRABOVSKY2024_tebabi_1imaoka1968.
• Figure 2: Spectral dispersion of refractive index (black lines) and extinction coefficient (red lines) of TeO2--BaO--Bi2O3 (TeBaBi) glasses. The bottom part displays the comparison of TeBaBi (this study) and TeO2--ZnO--BaO (TZB) glasses from Ref.HRABOVSKY2024_tzboptika of approximately equivalent concentration (in at.%) of the individual constituents with optical constants of pure TeO2 glass hrabovsky_pureTeO2. Note, that spectral dispersion of optical constants for pure TeO2 covers only the wavelength range 193--11,000 nm.
• Figure 3: Comparison between spectral dispersion of refractive index (black line) and extinction coefficient (red line) modeled by Tauc-Lorentz and Sellmeir optical model (open circles) for sample Te70Ba20Bi10 (top part) and spectral dispersion of refractive index of all synthesized TeO2--BaO--Bi2O3 (TeBaBi) glasses approximated by Sellmeir model (bottom part).
• Figure 4: Evolution of glass density, $\rho$, (taken from Ref.HRABOVSKY2024_tebabi_1) refractive index, $n_{1550}$, and Verdet constant, $V_{632}$, with respect to chemical composition of TeO2--BaO--Bi2O3 (TeBaBi) glass.
• Figure 5: (a) Spectral dispersion of Verdet constant of TeO2--BaO--Bi2O3 glasses (TeBaBi) and (b) compositional evolution of magneto-optic anomaly scalling parameter,$\gamma$.