Three azo-dyes, 4′-{[(2-hydroxylethyl)methyl]amino}-4-nitroazobenzene(1), 1-[4-(4′-nitrophenyl)-azophenyl]-3,5-biphenyl-2-pyrazoline(2) and 1-[4-(4′-nitrophenyl)-azophenyl]-5-(4′-hydroxylphenyl)-3-phenyl-2-pyrazoline(3) were synthesized. The polarized photoinduced birefringence and relaxation process of those azo-dyes doped with PMMA films were investigated under polarized laser intensity. The results indicate that compounds with pyrazoline group have a high storage rate and thermal stability. It has been found that the birefringence signals decrease with the increase of the temperature, but the effect of temperature is different for the three compounds. Compounds 2 and 3, with pyrazoline groups have a good thermal stability at room temperature, and compound 3 can even keep 30% of its maximum birefringence at 90 ℃.
