Ms. Suresh Kumar Jakka Profile

Suresh Kumar Jakka

at Univ de Aveiro

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Proceedings Article | 29 March 2011 Paper

Role of Yb3+ ions in the IR to visible upconversion of Er3+ ions in LTT glasses

A. Mohan Babu, J. Suresh Kumar, B. C. Jamalaiah, Neeraj Kumar Giri, S.B. Rai, L. Rama Moorthy

Proceedings Volume 7940, 79400J (2011) https://doi.org/10.1117/12.874860

KEYWORDS: Glasses, Ions, Absorption, Upconversion, Erbium, Visible radiation, Fiber amplifiers, Luminescence, Lead, Tungsten

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In order to develop efficient visible upconversion lasers and optical fiber amplifiers, the detailed spectroscopic properties of singly doped Er³⁺ and codoped Er³⁺-Yb³⁺ ions in lead tungsten tellurite (LTT) glasses have been investigated. The glasses were prepared by the conventional melt quenching technique. Absorption, visible upconversion spectra and NIR emission spectra were recorded as a function of Yb³⁺ ions concentrations. Judd-Ofelt (J-O) analysis has been performed for the spectral intensities of Er³⁺and Er³⁺-Yb³⁺ absorption bands. Spontaneous emission probabilities (A_R), radiative lifetimes (τ_R) and branching ratios (β_R) were calculated by using the phenomenological Judd-Ofelt intensity parameters. Three strong upconversion emission bands centered at 526, 551 and 665 nm were observed under 980nm excitation, due to the energy transfer process from Yb³⁺ to Er³⁺ ions. The green emissions centered at 526 and 551 nm and the red emission at 665 nm are attributed to ²H_11/2→ ⁴I_15/2, ⁴S_3/2→ ⁴I_15/2 and ⁴F_11/2→ ⁴I_15/2 transitions of Er³⁺ions respectively. The relative intensity variations of ²H_11/2→ ⁴I_15/2, ⁴S_3/2→ ⁴I_15/2 and ⁴F_9/2→ ⁴I_15/2 transitions have been explained on the basis of the increase in the population accumulation rates of ²H_11/2 ,⁴F_9/2 and ⁴S_3/2 levels. The peak stimulated emission cross-section (σe) and gain bandwidth parameter (σe×▵λ_eff) of ⁴I_13/2 → ⁴I_15/2 transition at 1.54 μm for Er³⁺ and Er³⁺-Yb³⁺ ions in LTT glasses have been determined and compared with different glass hosts. The stimulated emission cross-sections (σ_e) determined by using McCumber theory for the ⁴I_13/2 → ⁴I_15/2 transition are compared with the measured (σ_e) values obtained from the emission data. The results of these investigations revealed that the lead tungsten tellurite (LTT) glasses could be more useful as promising host materials for the design and development of optical fiber amplifiers and upconversion lasers.

Proceedings Article | 23 March 2011 Paper

Concentration dependent luminescence characteristics of 5D4 and 5D3 excited states of Tb3+ ions in CFB glasses

J. Suresh Kumar, K. Pavani, T. Sasikala, M. Jayasimhadri, Kiwan Jang, L. Rama Moorthy

Proceedings Volume 7940, 79401H (2011) https://doi.org/10.1117/12.874933

KEYWORDS: Ions, Glasses, Absorption, Luminescence, Terbium, Oscillators, Energy transfer, Autoregressive models, Calcium, Quantum efficiency

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Calcium fluoroborate (CFB) glasses doped with different concentrations of Tb³⁺ ions have been prepared with molar composition of (42-x) B₂O₃ + 20 CaF₂ +15 CaO + 15 BaO + 8 Al₂O₃ + x TbF₃ (x=0.05, 0.1, 0.5, 1.0, 2.0 and 4.0) by melt quenching method. Optical absorption spectrum for 1.0 mol% of Tb³⁺:CFB glass was recorded in UV-Vis-NIR regions. Radiative parameters such as radiative transition probabilities (A_R), radiative lifetimes (τ_R), radiative branching ratios (β_R) for the ⁵D₃ and ⁵D₄ excited states have been calculated by using the Judd-Ofelt parameters (Ω_λ=2,4,6). The luminescence spectra recorded for different concentrations of Tb³⁺ ions in CFB glasses exhibit seven and four bands originating from ⁵D₄ and ⁵D₃ excited states respectively. As the concentration of Tb³⁺ ions increases the intensities of luminescence peaks originating from ⁵D₄ state increases, whereas, the quenching of intensities has been observed for the emission peaks originating from ⁵D₃ state due to energy transfer through cross-relaxation channel (⁵D₃ : ⁷F₆) → (⁵D₄ : ⁷F₀). The experimental lifetimes of ⁵D₄ state for all the concentrations of Tb³⁺ ions are equal and exhibit single exponential decay with highest quantum efficiency which confirms that these glasses can be used for high intensity green emission even at high concentrations of Tb³⁺ ions.

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