LaViolette Aaron K, Ouzounov Dimitre G, Xu Chris
School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA.
Biomed Opt Express. 2023 Jul 28;14(8):4369-4382. doi: 10.1364/BOE.498214. eCollection 2023 Aug 1.
Measurements of three-photon action cross-sections for fluorescein (dissolved in water, pH ∼11.5) are presented in the excitation wavelength range from 1154 to 1500 nm in ∼50 nm steps. The excitation source is a femtosecond wavelength tunable non-collinear optical parametric amplifier, which has been spectrally filtered with 50 nm full width at half maximum band pass filters. Cube-law power dependance is confirmed at the measurement wavelengths. The three-photon excitation spectrum is found to differ from both the one- and two-photon excitation spectra. The three-photon action cross-section at 1154 nm is more than an order of magnitude larger than those at 1450 and 1500 nm (approximately three times the wavelength of the one-photon excitation peak), which possibly indicates the presence of resonance enhancement.
给出了荧光素（溶解于水，pH值约为11.5）在1154至1500 nm激发波长范围内以约50 nm步长的三光子作用截面测量结果。激发源是一个飞秒波长可调谐非共线光学参量放大器，已通过半高全宽为50 nm的带通滤波器进行光谱滤波。在测量波长处证实了立方律功率依赖性。发现三光子激发光谱与单光子和双光子激发光谱均不同。1154 nm处的三光子作用截面比1450和1500 nm处的大一个数量级以上（约为单光子激发峰波长的三倍），这可能表明存在共振增强。
