Effects of metallization and bromination on nonlinear optical properties of diphenylporphyrins

Nonlinear refraction and nonlinear absorption of diphenylporphyrins with bromination and metallization were studied by Z-scan technique in nanosecond and picosecond regimes. Results show that both metallization and bromination of diphenylporphyrins can cause the regular change of magnitude and sign of nonlinear absorption. The transition between saturable absorption and reverse saturable absorption happens as bromine increases and metal ion changes. The effect of bromination on nonlinear refraction is small, the change of nonlinear refraction is mainly attributed to the metallization. Influences of photophysical parameters on nonlinear absorption and nonlinear refraction have been elucidated using five-level models.