Femtosecond laser induced optical second harmonic generation in pulsed laser deposited VO2 thin films

• Published in: Optical and quantum electronics 2023-09, Vol.55 (9), Article 783
• Main Authors: Lafane, S., Neethling, P. H., Khereddine, Y., Malek, S., Abdelli-Messaci, S.
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Characterization and Evaluation of Materials; Computer Communication Networks; Crystal defects; Crystallites; Electrical conduction; Electrical Engineering; Electrical measurement; Electrical properties; Glass substrates; Lasers; Metal-insulator transition; Optical Devices; Optics; Photonics; Physics; Physics and Astronomy; Pulsed laser deposition; Pulsed lasers; Raman spectroscopy; Sapphire; Second harmonic generation; Thin films; Titanium; Transition temperature; Vanadium dioxide; Vanadium oxides; Vibration mode
• ISSN: 0306-8919; 1572-817X
• DOI: 10.1007/s11082-023-05029-8

Vanadium dioxide (VO 2 ) is a material that undergoes a first-order metal–insulator transition and belonging to the centrosymmetric class of materials for which the generation of the second order nonlinearities is forbidden. Optical second harmonic generation (SHG) has been demonstrated for the first time from VO 2 thin films using 800 nm femtosecond Ti:Sapphire laser. The VO 2 films used for the experiments were grown by pulsed laser deposition technique on two different substrates, glass and alumina, with different parameters leading to the growth of VO 2 films of different quality. The film grown on a glass substrate showed an enhanced SH signal but deviated from standard structural and thermo-electrical properties. X-ray diffraction, Raman spectroscopy and Atomic force microscopy analysis indicated, respectively, purity and finite crystallite size, red shifted VO 2 vibrational modes and nanocrystalline nature of the film. The thermo-electrical measurements showed a low resistivity, activation energy of electrical conduction and transition temperature, reduced transition contrast, and broadened hysteresis width. Contrary, the one grew on an alumina substrate resulted in improved microstructural and thermo-electrical properties of the transition, and displayed a noticeably weaker SH signal. In addition to the well-known surface and interface effects on the generation of SH, these outcomes indicate the contribution of defects to SH conversion efficiency in VO 2 thin films. The generation of SH in VO 2 thin films presents new opportunities for material analysis and device fabrication.