Defect-mediated nonlinear absorption properties of wide-bandgap silicon-doped aluminum nitride thin films for visible optical limiting applications
Optical Materials, cilt.178, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 178
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.optmat.2026.118243
- Dergi Adı: Optical Materials
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Applied Science & Technology Source, Chimica, Compendex, INSPEC, Academic Search Ultimate (EBSCO), Engineering Source (EBSCO)
- Anahtar Kelimeler: Defect states, Nonlinear absorption, Optical limiting, Si-doped AlN films, Z-scan
- Sivas Cumhuriyet Üniversitesi Adresli: Evet
Özet
In this study, the nonlinear optical response and optical limiting performance of a Si-doped AlN films grown on sapphire substrate by Metal Organic Vapor Phase Epitaxy (MOVPE) were systematically examined. The optical bandgaps of the synthesized films were evaluated as 5.97-6.10 eV range, while the Urbach energies associated with structural defects, lattice disorder, and thermal effects were estimated to be 0.11-0.22 eV. Nonlinear absorption (NA) characteristics were investigated using open-aperture (OA) Z-scan experiments under 400 nm excitation (photon energy of 3.10 eV) at 70 fs pulse duration. The results indicate that two-photon absorption (TPA) is the primary nonlinear mechanism governing the optical response. To elucidate the role of defect-related states, the experimental data were analyzed using two distinct theoretical approaches: a conventional TPA-based model and an extended model incorporating one-photon absorption (OPA), TPA, and free-carrier absorption (FCA). The effective nonlinear absorption coefficients (βeff ) obtained from the extended model were consistently higher than those derived from the TPA-only model (β), demonstrating that defect-assisted absorption processes enhance the overall nonlinear response. Additionally, the Si-doped AlN films exhibit competitive optical limiting thresholds of 12.2 × 10− 3, 25.1 × 10− 3, and 18.9 × 10− 3 J/cm2 at 2275 GW/cm2 input intensity, highlighting their strong attenuation capability under high-intensity illumination. Despite lower thresholds in some composite nanomaterials, our results remain competitive due to the superior structural stability of III-nitrides. These findings suggest that these films are a promising candidate for optical limiting applications in the visible spectral range.