探索溶液中双光子过程的控制参数。
Exploring control parameters of two photon processes in solutions.
作者信息
Goswami Debabrata, Nag Amit
机构信息
Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India.
出版信息
J Chem Sci (Bangalore). 2012 Jan 1;124(1):281-289. doi: 10.1007/s12039-012-0227-3.
Two-photon microscopy depends extensively on the two-photon absorption cross-sections of biologically relevant chromophores. High repetition rate (HRR) lasers are essential in multiphoton microscopy for generating satisfactory signal to noise at low average powers. However, HRR lasers generate thermal distortions in samples even with the slightest single photon absorption. We use an optical chopper with HRR lasers to intermittently 'blank' irradiation and effectively minimize thermal effects to result in a femtosecond z-scan setup that precisely measures the two-photon absorption (TPA) cross-sections of chromophores. Though several experimental factors impact such TPA measurements, a systematic effort to modulate and influence TPA characteristics is yet to evolve. Here, we present the effect of several control parameters on the TPA process that are independent of chromophore characteristics for femtosecond laser pulse based measurements; and demonstrate how the femtosecond laser pulse repetition rate, chromophore environment and incident laser polarization can become effective control parameters for such nonlinear optical properties.
双光子显微镜在很大程度上依赖于生物相关发色团的双光子吸收截面。高重复率（HRR）激光器对于多光子显微镜至关重要，以便在低平均功率下产生令人满意的信噪比。然而，即使有最轻微的单光子吸收，HRR激光器也会在样品中产生热畸变。我们使用带有HRR激光器的光学斩波器间歇性地“遮蔽”照射，并有效最小化热效应，从而得到一种飞秒z扫描装置，该装置能精确测量发色团的双光子吸收（TPA）截面。尽管有几个实验因素会影响这种TPA测量，但尚未形成对TPA特性进行调节和影响的系统方法。在此，我们展示了几个控制参数对基于飞秒激光脉冲测量的TPA过程的影响，这些参数与发色团特性无关；并证明了飞秒激光脉冲重复率、发色团环境和入射激光偏振如何能够成为控制这种非线性光学特性的有效参数。
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