CONTINUOUS-WAVE DIODE-LASER INDUCED 2-PHOTON FLUORESCENCE EXCITATION OF 3 CALCIUM INDICATORS

Continuous wave (CW) diode laser induced two-photon fluorescence spect ra have been measured for calcium indicators of Indo-1, Oregon-green, and Fluo-3. The near 2.0 log-log power-dependence of fluorescence inte nsity versus incident laser power indicates that the fluorescence from these three calcium indicators was excited by two-photon absorption p rocess of 809-nm laser light. Calcium-dependent emission spectra of In do-1 and Oregon-green for two-photon excitation under wavelength of 80 9-nm have also been measured.