Research On Optical Limiting Effects Of Fullerene Solution And Aluminum-doped Zinc Oxide Film

With the rapid development of high-power lasers,more and more attention has been paid to the research of laser protection technology and the exploration of economical and practical laser protection materials.At present,laser protection technology based on nonlinear optics and optical limiting materials have been studied in the visible light band,but there are few studies on optical limiting materials that achieve laser protection in the near-infrared band.Studies have shown that fullerene(C₆₀ and C₇₀)and aluminum-doped zinc oxide?AZO?have strong nonlinear optical effects at visible wavelengths,but the nonlinear optical effects in the near-infrared band have yet to be studied.In this thesis,the optical limiting effects of fullerene solution and AZO film at the wavelength of1064nm are investigated.Different fullerene solutions(C₆₀ in toluene,C₆₀ in xylene,C₇₀ in toluene and C₇₀ in xylene)with two concentrations?0.25 and 1 mmol/L?and two thicknesses?5 and 10 mm?are used as samples.Taking the AZO film as sample,we have completed the open-aperture and close-aperture Z-scan measurement with different pulse widths?26,62 and 101 ns?and different energy densities?5.3,10.6 and 15.9 J/cm²?.The nonlinear absorption coefficients and the nonlinear refractive index coefficients were calculated.The effects of pulse width and energy density on nonlinear optical effects were analyzed,compared with other films with nonlinear optical effects.The results show that under the 1064 nm nanosecond pulsed laser,when the power density of incident light is less than 20MW/cm²,the transmittance of fullerene solution is above 0.8.When the incident light power density is higher than 20MW/cm²,and when the fullerene solution solute and solvent are certain,the transmittance of the solution generally becomes lower and the optical limiting effect becomes stronger with the increase of solution concentration and thickness.When the incident light power density is high,and when the fullerene solution concentration and thickness are constant,the transmittance of C₇₀ is generally lower than that of C₆₀,and thus the optical limiting effect of C₇₀is stronger than that of C_60.The transmittances of the toluene and xylene solvent samples are not much different,and the difference in solvent has little effect on the optical limiting effect.The average nonlinear absorption coefficient of AZO thin films is 3.68×10^-9 m/W,and the main nonlinear absorption effect is reverse saturated absorption;the average nonlinear refractive index coefficient is-6.34×10^-13 m²/W,and the main nonlinear refractive effect is self-defocusing.The pulse width and energy density of the incident laser have little effect on the nonlinear absorption coefficient and the nonlinear refractive index coefficient of the AZO film.Compared with other films with nonlinear optical effects,AZO has a larger order of magnitude of nonlinear optical coefficients and is expected to become optical limiting materials.