Two-photon nonlinear process induced fluorescence of Rhodamine 6G (R6G), Rhodamine B (RB), and their mixed aqueous solutions in mass proportion of 1:1, is experimentally observed by different exciting wavelengths. It shows that, for each sample, the exciting wavelength can influence the fluorescence intensity considerably but only slightly influence the peak wavelength of the spectrum. The optimal exciting wavelengths of R6G and the mixed dyes are around 700 nm. While for RB, the optimal exciting wavelengths can be 700 nm and 620 nm. For each dye sample, the spectral red-shift will occur as increase of the solution concentration. The mixing of the two dyes will cause the spectral red-shift with regard to the single dye under our experimental conditions. Moreover, in comparison, at lower concentrations, the mixed dye has relatively intense fluorescence. This work is of significance for determining the optimal exciting wavelength and developing the tunable two-photon dye lasers.

在不同的激发波长下，通过实验观察到了双光子非线性过程中若丹明6G（R6G），若丹明B（RB）及其混合水溶液的荧光，其荧光比为1：1。它表明，对于每个样品，激发波长可以显着影响荧光强度，但仅轻微影响光谱的峰值波长。R6G和混合染料的最佳激发波长约为700 nm。而对于RB，最佳激发波长可以是700 nm和620 nm。对于每种染料样品，光谱红移将随着溶液浓度的增加而发生。在我们的实验条件下，两种染料的混合将导致单一染料的光谱红移。而且，相比之下，在较低的浓度下，混合染料具有较强的荧光。这项工作对于确定最佳激发波长和开发可调谐双光子染料激光器具有重要意义。