Reverse Polarizability of Rare Earth Ions (La3+, Gd3+, Lu3+, Y3+) in Tellurite Glasses and Glass Ceramics for Optical Limiting

• Published in: ACS applied optical materials 2024-11, Vol.2 (11), p.2262-2276
• Main Authors: Patra, Pritha, Gangareddy, Jagannath, Jayanthi, K., Chakraborty, Saswata, Keshri, Shweta R., Bysakh, Sandip, Krishnan, N. M. Anoop, Soma, Venugopal Rao, Kalyandurg, Annapurna
• Format: Article
• Language: English
• Subjects: amorphous materials; ceramics; lasers; nonlinear optics; optical limiting; optical properties; rare earths; tellurite glass ceramics; third-order nonlinearity; z-scan
• ISSN: 2771-9855; 2771-9855
• DOI: 10.1021/acsaom.4c00326

All-optical modulation using inherent third-order optical nonlinearity of a medium has garnered considerable interest in photonics and optoelectronics. Herein, nonlinear optical (NLO) properties of tellurite glasses and glass ceramics (GCs) containing four different rare earths (RE = La, Gd, Lu, and Y) have been deliberated in near-infrared regions under an ultrafast regime. The La-based glass exhibits ∼10 times higher nonlinear refraction (n 2) and absorption (α2) than reported NLO materials. The NLO susceptibility [χ(3)] trend in the studied glasses is La > Gd > Lu > Y, matching with RE3+ polarizability. Furthermore, Ln2Te6O15 nanocrystallite-embedded transparent GCs exhibit a larger NLO coefficient due to the enhanced local field from oxygen vacancies in crystallites. Interestingly, the trend of χ(3) in GCs follows the sequence of Y > Lu > Gd > La, precisely opposite to the glasses. This observation challenges the general polarizability approach of RE3+ ions, emphasizing that quadratic hyperpolarizability of RE3+ is pivotal for NLO properties of GCs. Among the studied matrices, Y-containing GCs showed the lowest optical limiting (OL) threshold (5.4 mJ/cm2 at 800 nm), much lower than those of the reported NLO materials, suggesting its potential as a femtosecond NIR-laser safety material. A combination of large α2 and n 2 from the studied matrices indicates their advantage for harmonic generation, potentially aiding in the design of ultrafast signal processing devices.