Study On Two-photon Fluorescence Process Of Rhodamine B By Shaping Femtosecond Laser

In recent years,the application of shaping femtosecond laser in molecular-level medicine has received widespread attention.In the fields of fluorescence imaging,laser treatment of tumors,and laser surgery,The shaping femtosecond laser has opened a new door for us,allowing us to get a glimpse into the more subtle natural world,which will play an important role in biomedical applications.In this paper,the two-photon fluorescence process of Rhodamine B ethanol solution was studied in conjunction with shapingfemtosecond lasertechnology,and the fluorescence spectrum and intensity were modulated.In this paper,the two-photon fluorescence spectra of Rhodamine B in the ethanol solution under the irradiation of transform limited femtosecond laser first studied.By comparing the fluorescence spectra of Rhodamine B solution with four different concentrations,we found that the fluorescence spectra were redshifted with the increase of the concentration.At the same time,we studied the variation of the two-photon fluorescence intensity of Rhodamine B with the laser energy at different concentrations.The experimental curve can be fitted by quadratic function,and further prove that the fluorescenceemissionof Rhodamine B solution is a two-photon absorption process.In addition,we also studied the dependence of the two-photon fluorescence intensity on the laserellipticity.The experimental results show that under linear polarization conditions,the corresponding fluorescence intensity of Rhodamine B solution is the strongest.In the research of two-photon fluorescence in shaping femtosecond laser,using femtosecond laser spectrum phase shaping technology,we studied the coherent control of two-photon fluorescence in Rhodamine B solution.By performing π-phase scanning on the femtosecond laser pulse,the coherent control of two-photon fluorescence in Rhodamine B solution is achieved.Combined with the two-photon absorption theoretical model,the interference between different quantum channels during the two-photon absorption process is responsible for the modulation regulation of the fluorescence intensity.The theoretical simulation results are consistent with the experimental results.By applying the Sin phase to the femtosecond laser and changing the values of its parameters A and T,two-dimensional graphs of the two-photon fluorescence intensity in the Rhodamine B solution showed multiple slanted straight lines.At the same time,the fluorescence intensity changes more obviously with some specific parameter.Similar to the modulation principle of the two-photon fluorescence intensity of Rhodamine B under π phase scanning,the change in the two-photon fluorescence intensity obtained by Sin phase modulation is also due to the interference constructiveness and interference cancellation between different quantum paths during the two-photon transition.