Nonlinear optical properties of an azo-based dye irradiated by picosecond and nanosecond laser pulses

The nonlinear optical properties of an azo-based dye were investigated using Z-scan technique employing 38 ps pulses at 532 and 1064 nm, and 6 ns laser pulses at 532 nm. Large nonlinear absorption and nonlinear refraction were observed at both ps and ns 532 nm in the azoic dye. When excited at ps 1064 nm, this dye displayed a large two-photon absorption cross-section (σ2=1810 GM). Meanwhile, the optical nonlinearity mechanism was discussed in terms of molecular structure, excitation wavelength, and pulse width.

Research Highlights
► In this study we have investigated the nonlinear optical properties of an H-shaped azo-based dye.
► Our experimental results indicate that this kind of dye owns large nonlinear absorption and nonlinear refraction under both ps and ns 532 nm excitation.
► We find this dye has large two-photon absorption cross section (=1810▒GM) at ps 1064▒nm due to its special molecular structure.
► We have discussed the optical nonlinearity mechanism in terms of molecular structure, excitation wavelength and pulse width.