TY - JOUR
T1 - Three-photon excitation of 2,5-bis (4-biphenyl) oxazole
T2 - Steady state and time resolved intensities and anisotropies
AU - Gryczynski, Ignacy
AU - Malak, Henryk
AU - Hell, Stefan W.
AU - Lakowicz, Joseph R.
PY - 1996
Y1 - 1996
N2 - Three-photon excitation of 2,5-bis(4-biphenyl) oxazole (BBO) was observed when it was excited with the fundamental output of a femtosecond Ti:sapphire laser above 820 nm. The emission spectrum of BBO was identical for one-, two-, and three-photon excitation at 320, 640, and 960 nm, respectively. In toluene and triacetin, the emission intensity of BBO depended on the square of the laser power for wavelengths below 820 nm and displayed a sharp transition to a cubic dependence at longer wavelengths. The spatial distribution of the emission of BBO with three-photon excitation was more strongly localized than for two-photon excitation of a coumarin fluorophore at the same wavelength. The same single exponential intensity decay was observed for one-, two-, and three-photon excitation. However, the frequency domain anisotropy decay with three-photon excitation at 960 nm revealed a larger time-zero anisotropy, larger differential polarized phase angle, and larger modulated anisotropy than is possible for two-photon excitation with colinear oscillators. In triacetin, the anisotropy is not constant for three-photon excitation at different wavelengths. Surprisingly, the fluorescence intensities for three-photon excitation were only about 100-fold less than for two-photon excitation. The increasing availability of Ti:sapphire lasers suggests that multiphoton excitation can become a common tool in fluorescence spectroscopy.
AB - Three-photon excitation of 2,5-bis(4-biphenyl) oxazole (BBO) was observed when it was excited with the fundamental output of a femtosecond Ti:sapphire laser above 820 nm. The emission spectrum of BBO was identical for one-, two-, and three-photon excitation at 320, 640, and 960 nm, respectively. In toluene and triacetin, the emission intensity of BBO depended on the square of the laser power for wavelengths below 820 nm and displayed a sharp transition to a cubic dependence at longer wavelengths. The spatial distribution of the emission of BBO with three-photon excitation was more strongly localized than for two-photon excitation of a coumarin fluorophore at the same wavelength. The same single exponential intensity decay was observed for one-, two-, and three-photon excitation. However, the frequency domain anisotropy decay with three-photon excitation at 960 nm revealed a larger time-zero anisotropy, larger differential polarized phase angle, and larger modulated anisotropy than is possible for two-photon excitation with colinear oscillators. In triacetin, the anisotropy is not constant for three-photon excitation at different wavelengths. Surprisingly, the fluorescence intensities for three-photon excitation were only about 100-fold less than for two-photon excitation. The increasing availability of Ti:sapphire lasers suggests that multiphoton excitation can become a common tool in fluorescence spectroscopy.
KW - Fluorescence
KW - Frequency domain
KW - Three-photon excitation
KW - Ti:sapphire laser
KW - Time resolved
KW - Two-photon excitation
UR - http://www.scopus.com/inward/record.url?scp=0000951138&partnerID=8YFLogxK
U2 - 10.1117/12.250670
DO - 10.1117/12.250670
M3 - Article
AN - SCOPUS:0000951138
SN - 1083-3668
VL - 1
SP - 473
EP - 480
JO - Journal of Biomedical Optics
JF - Journal of Biomedical Optics
IS - 4
ER -