Tailoring SHG Efficiency via t‐Te Nanocrystals in Tellurite Glasses by Femtosecond Laser Micromachining

ABSTRACT In this study, we propose a strategy to enhance and modulate second‐harmonic generation (SHG) in tellurite‐zinc (TZ) glasses via femtosecond (fs) laser microfabrication, with and without the incorporation of BaTiO 3 :Er/Yb/Zn nanoparticle (TZ‐NP). Fs‐laser irradiation at varied fluences induces structural modifications, as revealed by Raman spectroscopy and mapping, including an increase in the I(TeO 3 )/I(TeO 4 ) ratio (∼15% in TZ and ∼21% in TZ‐NP), indicative of network depolymerization, NBO formation, and densification. Trigonal tellurium (t‐Te) nanocrystals nucleate and grow under irradiation, exhibiting a chiral, non‐centrosymmetric structure, as evidenced by the emergence of A 1 and E TO Raman modes (∼120 cm −1 and ∼140 cm −1 ), XRD peaks matching the P3 1 21 t‐Te phase, and HRTEM showing nanocrystals expanding from ∼8 nm to ∼16 nm with increasing pulse number. Complementary atomic‐resolution imaging and SAED confirm lattice ordering and long‐range periodicity along [001], reinforcing the formation of non‐centrosymmetric, SHG‐active domains. Optical and confocal imaging under 850 nm and 980 nm excitation reveal localized SHG and, in TZ‐NP, upconversion luminescence, with SHG intensity peaking at 1.9 J/cm 2 in TZ (850 nm) and reaching 3.3 J/cm 2 (850 nm) and 4.2 J/cm 2 (980 nm) in TZ‐NP. Quantitative scaling laws (I 2ω ∝ F m ) and a figure of merit () further confirm nanoparticle‐induced enhancement of SHG efficiency. These results demonstrate that fs‐laser‐induced crystallization of t‐Te, combined with local field enhancement from perovskite nanoparticles, enables efficient and tunable SHG in tellurite‐based glasses, offering new avenues for integrated nonlinear photonic platforms.