Nonlinear self-trapping and fluorescence excitation in Chlorophyll solution

Chlorophyll, an essential pigment for photosynthesis, is abundant in plants, algae, and cyanobacteria. Over the past few decades, research has primarily focused on its unique roles in photosynthesis, however, the nonlinear light interaction with chlorophyll is highly unexplored. We report on the nonlinear optical interplay of light with the chlorophyll solution at different concentrations. In this solution with biologically small organic molecules, we observed nonlinear self-trapping as a laser beam propagates through the chlorophyll solution. Moreover, the magnitude of the optical nonlinearity also depends on the chlorophyll concentration. In addition, the chlorophyll solution produces red fluorescence covering the self-induced waveguide channel and the propagation mode is consistent with the laser. By inspecting the spectra of the fluorescence, we discover that the power at which chlorophyll reaches saturation closely aligns with the optimal power for self-trapping. Our findings on light self-guiding in biological molecule media may open the door to biophotonic applications, contributing to green development across multiple industries.