Abstract Laser excitation and intensity-dependent third-order nonlinear optical (NLO) absorption properties of 2-amino 5-nitropyridinium dihydrogen phosphate (2A5NPDP) in both pulsed (532 nm, 5 ns, 100 µJ) and continuous wave (532 nm, 50 mW) regime were studied by Z-scan experiment. Under CW laser excitation, 2A5NPDP exhibits saturable absorption (SA) ascribed to be of thermo-optic origin. Interestingly the sample show reverse saturable absorption (RSA) due to genuine two-photon absorption (2PA) process under nano pulsed laser excitation. Earlier thermodynamic properties such as thermal conductivity (51 W/m.K), specific heat capacity (3894 J/Kg.K) and thermal diffusivity (7.5 × 10−6 m2/s) were estimated theoretically from the DSC curves. Thus 2A5NPDP with excellent thermal stability and high NLO coefficients can be utilized as an energy-absorbing optical limiter and saturable absorber under nano pulsed and CW green laser excitation.

中文翻译：

---

2-氨基5-硝基吡啶鎓磷酸二氢盐的激光激发相关非线性吸收

摘要 2-氨基 5-硝基吡啶二氢磷酸盐 (2A5NPDP) 在脉冲 (532 nm, 5 ns, 100 µJ) 和连续波 (532 nm, 50 mW) 方案通过 Z 扫描实验进行研究。在连续激光激发下，2A5NPDP 表现出可饱和吸收 (SA)，归因于热光起源。有趣的是，由于在纳米脉冲激光激发下真正的双光子吸收 (2PA) 过程，样品显示出反饱和吸收 (RSA)。早期的热力学性质，如导热系数 (51 W/mK)、比热容 (3894 J/Kg.K) 和热扩散系数 (7.5 × 10−6 m2/s)，是从 DSC 曲线理论上估计的。