abstract
Structural and optical properties of antimony-containing sodium borate glasses were studied and their ultrafast third-order nonlinear optical (NLO) properties have been evaluated using Z-scan measurements with femtosecond (fs) pulses (similar to 150 fs, 80 MHz) at 750, 800, and 880 nm wavelengths. Glasses in the (mol %) 20Na(2)O (80 - x)B2O3 - xSb(2)O(3) (where x = 0, 10, 20, and 30) system have been fabricated via melt quench technique. The structural modifications were analyzed using the Raman and magic angle spinning (MAS)-nuclear magnetic resonance (NMR) (B-11 MAS-NMR and Na-23 MAS-NMR) techniques. The optical absorption spectra revealed that the absorption edge was red-shifted, suggesting the decrease in band gap energy with increase of antimony content in the glasses. Raman scattering results revealed that the boroxol rings are depressed with the incorporation of Sb2O3 for replacing B2O3. B-11 MAS-NMR results showed a progressive increase of B-4 units at the expense of B-3 units. The Raman and B-11 MAS-NMR results support the formation of Sb5+ ions due to oxidation of Sb3+ that played the role of charge compensation. Na-23 MAS-NMR spectra revealed a decreasing trend in the average of bond lengths of Na-O with increasing Sb2O3 contents. This suggested that sodium changed its role from charge compensator to modifier cation. The antimony-containing glasses demonstrated a reverse saturable absorption in open-aperture Z-scan mode due to two-photon absorption, while closed-aperture Z-scan signatures depicted positive nonlinear refraction due to self-focusing effect. The NLO coefficients were found to increase with Sb2O3 due to the increased nonbridging oxygens and also due to the hyperpolarizability of Sb3+ and Sb5+ ions. The observed NLO data clearly suggest that the investigated glasses are beneficial for optical limiting applications.
keywords
ULTRAFAST RESPONSE; REFRACTIVE-INDEX; RAMAN; NMR; GALLIUM; BI2O3; ABSORPTION; RELAXATION; MANGANESE; SPECTRA
subject category
Chemistry; Science & Technology - Other Topics; Materials Science
authors
Jagannath, G; Eraiah, B; Gaddam, A; Fernandes, H; Brazete, D; Jayanthi, K; Krishnakanth, KN; Rao, SV; Ferreira, JMF; Annapurna, K; Allu, AR
our authors
Allu Amarnath Reddy
PhD StudentAnuraag Gaddam
Assistant Researcher
Daniela Silva Brazete
Research Fellowship
José Maria da Fonte Ferreira
Retired Professoracknowledgements
G.J. is grateful to late Dr. Rajan V. Anavekar, Former Professor, Department of Physics, Bangalore University, Bangalore, India, for useful discussions and valuable suggestions. S.V.R. acknowledges DRDO, India, for financial support through ACRHEM. This work was also done within the scope of the project CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT ref UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020. A.R.A. and K.A. gratefully acknowledge the support and encouragement of Dr. K. Muraleedharan, Director, CSIR-CGCRI, and Dr. Ranjan Sen, Head, Glass Division, CSIR-CGCRI.