Defect Engineering of Ultrathin WO₃ Nanosheets: Implications for Nonlinear Optoelectronic Devices

Abstract

Ultrathin two-dimensional (2D) metal oxides have recently emerged as members of the 2D family with broad use in the catalytic field and energy storage techniques. However, investigations on their optoelectronic properties, nonlinear optical properties in particular, remain largely elusive. Defect (site) engineering had been a powerful tool to tailor semiconductor band gaps for their catalytic use, while, herein, it was carried out to expand the third-order nonlinear response of ultrathin 2D transition-metal oxide WO3 to the infrared region. By engineering the oxygen vacancy, WO3 demonstrated an indirect band gap adjustable from 2.33 eV (WO3) to 1.54 eV (D-WO3) with enhanced nonlinear saturable absorption extending from the visible to the near-infrared range, which have promising use in mode-locking, laser beam shaping, and ultrafast photonics. Transient absorption techniques revealed rapid fs-to-ps carrier dynamics followed by slower exciton bleaching on the μs time scale for the oxygen vacancy-rich metal oxides upon photoexcitation, which accounted for the origin of their strong and broad nonlinear optical responses. The strategy provided not only insights into the underlying photophysics of the 2D metal oxides but also fresh ammunition to bring out their remaining potential into full play, such as the fabrication of optoelectronic devices for nonlinear optics.

Third-order optical nonlinearities of two-dimensional SnS under irradiation: implications for space use

“…The detailed setup was described in our previous work. 46,47 The laser source for the fs Z-scan setup was a regenerative amplifier (1 kHz, 800 nm) seeded by one oscillator (120 fs, 80 MHz). The wavelengths (290-2600 nm) were generated from one optical parametric amplifier.…”

Flexible optical limiters based on Cu3VSe4 nanocrystals

“…The third-order nonlinear optical properties of the as-prepared Cu 3 VSe 4 NCs were investigated using the ns and fs Z-scan technique. [22][23][24] The Z-scan results of Cu 3 VSe 4 NCs and C60 at different incident laser energies of 532 nm and 1064 nm are shown in Fig. 2a and b and Fig.…”

Electronic state evolution of oxygen-doped monolayer WSe2 assisted by femtosecond laser irradiation

“…S3, ESI †). [44][45][46][47][48] It could be due to the electron transfer from oxidized areas (the defects like WO 3 clusters) to the rest of monolayer WSe 2 in the vicinity, forming n-doped monolayer WSe 2 and hole-dominant WO 3 . It is worth noting that the GSB peaks for C-exciton and A-exciton states of monolayer WSe 2 are always clearly observed under the Mott density condition, and the initial C-exciton signal in IFsLI case 2 even increases again, implying a higher initial carrier population in this band-nesting state.…”