Three- and four-photon absorption of a multiphoton absorbing fluorescent probe

Abstract

High-order multiphoton excitation processes are becoming a reality for fluorescence imaging and phototherapy treatment because they afford minimization of scattered light losses and a reduction of unwanted linear absorption in the living organism transparency window, making them less susceptible to photodamage, while improving the irradiation penetration depth and spatial resolution. We report the four-photon-excited fluorescence emission of (7-benzothiazol-2-yl-9,-didecylfluoren-2-yl)diphenylamine in hexane and its four-photon absorption cross section sigma4' = 8.1 x 10(-109) cm8 s3 photon(-3) for the transition S0 --> S1 when excited at 1600 nm with a tunable optical parametric generator (OPG) pumped by picosecond laser pulses. When pumped at 1200 nm, three-photon absorption was observed, corresponding to the same transition.

Three‐ and Four‐Photon Excitation of Poly(2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylenevinylene) (MEH‐PPV)

“…The 3PA absorption cross sections determined here are comparable, although one order of magnitude smaller, to those found in the literature for specially designed molecules. [16,[18][19][20][21] On the other hand, we obtained 4PA cross-section values of the same magnitude as those reported in the literature. [16,22] The strong three-and fourphoton-induced emission, combined with its well-established physical and chemical properties (photo-oxidation, thermal stability, etc.)…”

“…[16,[18][19][20][21] On the other hand, we obtained 4PA cross-section values of the same magnitude as those reported in the literature. [16,22] The strong three-and fourphoton-induced emission, combined with its well-established physical and chemical properties (photo-oxidation, thermal stability, etc.) and commercial availability, marks out MEH-PPV as a new material for photonics applications, for instance, in up-conversion lasers and fluorescence imaging.…”

“…The transmitted signal through the sample was monitored using a germanium photodetector coupled to a lock-in amplifier. By fitting the normalized transmittance data using the proper expression for each nonlinear process [16,17], the n-photon nonlinear absorption coefficient, a n , can be determined, provided only one nonlinear process occurs each time. The 3PA and 4PA cross sections, r 3PA and r 4PA , respectively, are determined through r nPA = a n (hm) n-1 /N 0 , where hm is the photon excitation energy and N 0 the number of molecules per cubic centimeter.…”

“…The 3PA spectrum of MEH-PPV was truncated at 1660 nm because competition between 3PA and 4PA occurs in this region, as will be discussed later when the multiphoton-excited fluorescence results are presented. The model adopted here to determine the n-photon absorption cross section [16,17] considers that only one nonlinear process takes place (e.g., 3PA or 4PA). Thus, we were not able to determine the 3PA and 4PA cross section between 1660 nm and 1760 nm.…”

Two-photon absorption and two-photon circular dichroism of hexahelicene derivatives: a study of the effect of the nature of intramolecular charge transfer

“…It is hard to explain this difference in amplitude considering that all experiments were performed in the femtosecond regime where excited state absorption is negligible. 71,72 Nevertheless, the chosen XCF reproduces very well the relative intensities between the main TPA bands, and it yields a suitable bandwidth and separation between the peaks.…”