Second harmonic generation in surface crystallized 30GeS2 · 35Ga2S3 · 35AgCl chalcohalide glasses

The infrared transmitting surface crystallized chalcohalide glasses containing nontoxic and excellent nonlinear optical AgGaGeS₄ crystallites were fabricated by heat-treatment of the as-prepared 30GeS₂ · 35Ga₂S₃ · 35AgCl chalcohalide glass at 350 °C (T_g −10 °C) for 24 h. An intensive second harmonic generation (SHG) was observed clearly using the Maker fringe technique, and the origin of SHG was mainly ascribed to the AgGaGeS4 nonlinear optical crystallites contained in the surface crystallized layer. The thickness of the surface crystallized layer showing SHG activation is approximate 50 μm. The χ⁽²⁾ susceptibility of the prepared surface crystallized 30GeS₂ · 35Ga₂S₃ · 35AgCl chalcohalide glass is calculated to be about 12.4 pm/V at a fundamental wavelength of 1064 nm, which indicates a promising nonlinear optical material in the infrared spectral region.     

Spectral analysis of RE (RE = Sm, Dy, and Tm): P2O5–Al2O3–Na2O glasses

Phosphate glasses in the compositions of 70P₂O₅–15Al₂O₃–14Na₂O–1RE³⁺ (RE = Sm, Dy, and Tm) (mol%) were prepared by melt-quenching technique and characterized optically. The differential thermal analysis (DTA) profile of the host glass was carried out to confirm its thermal stability. For all the glasses absorption, photoluminescence and decay measurements have also been carried out. These glasses have shown strong emission and absorption bands in visible and near-infrared (NIR) region. From the measured absorption spectra, Judd–Ofelt (J–O) intensity parameters (Ω₂, Ω₄ and Ω₆) have been calculated for all the studied ions. For Sm³⁺ doped glass, four emission bands centered at 562 nm (⁴G_5/2 → ⁶H_5/2), 598 nm (⁴G_5/2 → ⁶H_7/2), 644 nm (⁴G_5/2 → ⁶H_9/2), and 704 nm (⁴G_5/2 → ⁶H_11/2) have been observed with 402 nm (⁶H_5/2 → ⁴F_7/2) excitation wavelength. Of them, 598 nm (⁴G_5/2 → ⁶H_7/2) has shown a bright orange emission. With regard to Dy³⁺ doped glass, a blue emission band centered at 486 nm (⁴F_9/2 → ⁶H_15/2) and a bright yellow emission at 575 nm (⁴F_9/2 → ⁶H_13/2) have been observed, apart from 662 nm (⁴F_9/2 → ⁶H_11/2) emission transition with an excitation at 388 nm (⁶H_15/2 → ⁴I_13/2,⁴F_7/2) wavelength. Emission bands of 650 nm (¹G₄ → ³F₄) and 785 nm (¹G₄ → ³H₅) transitions for the Tm³⁺ doped glass, with an excitation wavelength at 466 nm (³H₆ → ¹G₄), have also been observed. The stimulated emission cross-sections of all the emission bands of RE³⁺ glasses (RE = Sm, Dy, and Tm) have been computed based on their measured full-width at half maximum (FWHM, Δλ) and measured lifetimes (τ_m).     

Optical band gap studies on xPb3O4–(1−x)P2O5 lead[(II, IV)] phosphate glasses

A series of glasses in the xPb₃O₄–(1−x)P₂O₅ (red lead phosphate) (RLP) system with ‘x' varying from 0.075 to 0.4 were prepared by the single-step melt quenching process from Pb₃O₄ and NH₄H₂PO₄. The optical absorption spectra of these glasses have been recorded in the ultraviolet region from 200 to 400 nm and the fundamental absorption edges have been identified. The optical band gap E_opt values have been determined for all the glasses using the known theories. The (E_opt) values vary from 4.90 to 3.21 eV the highest being 4.57 eV, corresponding to the most stable glass of x=0.225. The absorption edge is attributed to the indirect transitions and the origin of the Urbach energy ΔE is suggested to be thermal vibrations. These glasses promise as potential candidates for application in optical technology compared to simple xPbO–(1−x)P₂O₅ (lead phosphate) (LP) glasses.     

Structural and optical properties of (100 − x)(Li2B4O7) − x(SrO–Bi2O3–0.7Nb2O5–0.3V2O5) glasses and glass nanocrystal composites

Glasses of various compositions in the system (100 − x)(Li₂B₄O₇) − x(SrO–Bi₂O₃–0.7Nb₂O₅–0.3V₂O₅) (10  x  60, in molar ratio) were prepared by splat quenching technique. The glassy nature of the as-quenched samples was established by differential thermal analyses (DTA). The amorphous nature of the as-quenched glasses and crystallinity of glass nanocrystal composites were confirmed by X-ray powder diffraction studies. Glass composites comprising strontium bismuth niobate doped with vanadium (SrBi₂(Nb_0.7V_0.3)₂O_9−δ (SBVN)) nanocrystallites were obtained by controlled heat-treatment of the as-quenched glasses at 783 K for 6 h. High resolution transmission electron microscopy (HRTEM) of the glass nanocrystal composites (heat-treated at 783 K/6 h) confirm the presence of rod shaped crystallites of SBVN embedded in Li₂B₄O₇ glass matrix. The optical transmission spectra of these glasses and glass nanocrystal composites of various compositions were recorded in the wavelength range 190–900 nm. Various optical parameters such as optical band gap (E_opt), Urbach energy (ΔE), refractive index (n), optical dielectric constant and ratio of carrier concentration to the effective mass (N/m^*) were determined. The effects of composition of the glasses and glass nanocrystal composites on these parameters were studied.     

Scintillation properties of CsSrX3:Eu (CsSr1−yEuyX3, X = Cl,Br; 0 ≤ y ≤ 0.05) single crystals grown by the Bridgman method

The single crystals of CsSr_1−yEu_yCl₃ and CsSr_1−yEu_yBr₃ (0 ≤ y ≤ 0.05) grown by the Bridgman method have been investigated for their scintillation properties. The radioluminescence spectra of the crystals demonstrated a narrow band at 400–500 nm which peak position shifts continuously toward larger wavelength as the Eu²⁺ concentration increases. The scintillation light yield achieves maximal value of 33,400 ± 1700 photons per MeV with energy resolution of 11.5% at CsSr_0.95Eu_0.05Cl₃ and 31,300 ± 1600 photons per MeV with energy resolution of 9% at CsSr_0.95Eu_0.05Br₃. The decay times at room temperature are 2.7 ± 0.2 μs and 2.5 ± 0.2 μs, respectively.