Broadband Optical Limiting and Saturable Absorption Properties of Gallium Nitride Nanowires

This study explores the nonlinear absorption properties of gallium nitride (GaN) nanowires synthesized using the chemical vapor deposition method. We investigated their behavior across the ultraviolet, visible, and near-infrared wavelength range using a picosecond pulse laser. Our experimental results demonstrated the presence of two-photon absorption, excited by lasers at 266 nm, 355 nm, and 532 nm, and three-photon absorption, excited by a 1064 nm laser. Additionally, we observed a broadband saturable absorption phenomenon at these laser wavelengths. A detailed analysis of the electron transition mechanism was performed. The results indicated that GaN nanowires exhibit exceptional broadband optical limiting characteristics, achieving a minimum transmittance below 25%. Moreover, they showed remarkable saturable absorption properties, particularly in the ultraviolet-visible wavelength range, with modulation depths below 45%. Numerical simulations were conducted to determine parameters such as saturable absorption intensity, two-photon absorption coefficient, and three-photon absorption coefficient. The study concludes that GaN nanowires are excellent broadband optical limiting materials and effective saturable absorbers in the ultraviolet-visible wavelength range, making them promising candidates for applications in optical limiting and ultrafast photonics.