Two-Photon Absorption in Rhodamine 6G Occurring in Concert with Fluorescence Depletion

Abstract

Using two-color fluorescence dip spectroscopy, we observed two-photon absorption processes (TPA) in Rhodamine 6G occurring in concert with fluorescence depletion processes (FD). A nano-second pulse erase beam in the near-infrared region was applied to induce TPA together with FD. It was found that the fluorescence intensity strongly depends on the photon-flux of the erase beam and that the effective TPA cross-section for the nano-second laser pulse is smaller than that for a femto-second laser pulse. This phenomenon can be interpreted as resulting from FD induced by a multiple-excitation process.

Cross-Term Selective, Two-Pulse Correlation Measurements by Phase-Shifted Parallel Modulation for Analysis of a Multi-Photon Process

“…Intensity was normalized to the correlation peak intensity obtained by the PPM technique. The observed fluorescence is caused by the two-photon excitation because pump photon energy (wavelength of 800 nm) is lower than the S 1 ← S 0 transition energy 15,16 of Rh6G, which has an absorption peak at approximately 530 nm, and the second-order pump power dependence was confirmed by our experimental system. The dot-dash line in the Fig.…”

“…As a candidate for the origin of the negative background, the excitation saturation effects in the two-photon excitation 20 and the fluorescence depletion 15,16,21 were considered. Both saturation effect and fluorescence depletion can have a dramatic influence on the results of measurements when using two-photon-excited fluorescence such as fluorescence correlation spectroscopy and two-photon fluorescence microscopy.…”

“…In other words, the observed negative background was because of the fluorescence depletion caused by the up-conversion mechanism. 15,21,24 The results indicate that, when used in combination with the PPM technique, the two-pulse correlation is a powerful tool to find and analyze the photophysical dynamics buried in the two-photon excitation process. In particular, it is vital to find a weak intensity change caused by a higher-order optical process for the accurate interpretation of the results of two-photon-excited fluorescence measurements, such as fluorescence correlation spectroscopy and two-photon fluorescence 20,22,23 microscopy.…”

Fabricação de micro-ressonadores ópticos via fotopolimerização por absorção de dois fótons

“…devido ao seu intenso sinal de fluorescência, boa estabilidade química e suas propriedades não lineares. [69][70] Sua estrutura química é mostrada na Fig. 4.19, junto ao seu espectro de absorção e emissão.…”