Abstract

Frequency-domain interference of time-delayed pulses in inhomogeneously broadened, one-photon absorbing media has been exploited in the past for fast optical data storage, processing, and time-and-space domain holography.¹³ We have shown recently that spectral gratings can be created upon simultaneous two-photon absorption (TPA) from a pair of femtosecond pulses.^4,5 In this paper we study, for the first time to our knowledge, the dependence of the frequency-domain grating on the shape of homogeneous absorption spectrum of two-photon transition. We take advantage of the complete absence of Rayleigh scattering at twice the excitation frequency, which allows us to measure resonance fluorescence spectrum as a function of temperature. Ti:sapphire regenerative amplifier (CPA- 1000, Clark MRX) was used to pump an optical parametric amplifier, OPA, (TOPAS, Quan- tronix), which yielded 100-fs, ~100 pi near-IR pulses. Michelson interferometer divided each OPA pulse into two spatially overlapped but time-delayed, by At = 760 fs, pulses, which were focused on a chlorin-doped poly-(vynil butyral) film inside helium cryostat. Fluorescence was analyzed with a TRIAX 550 lobin Yvon/Spex spectrometer coupled with a CCD detector.

© 2002 Optical Society of America