Characterization of ultra-weak fluorescence using picosecond non-collinear optical parametric amplifier

We report a technique for characterization of ultra-weak fluorescence based on a 355-nm pumped picosecond non-collinear optical parametric amplifier (OPA). In the experiment, we effectively reduced the strong super-fluorescence background by using a series of methods. With the picosecond OPA as the pre-amplifier and the gating pulse, the decay of the fluorescence of Rhodamine 6G dye in ethanol was measured and the fluorescence lifetime was found to be about 941 ps. The gain factor of this parametric fluorescence amplifier was measured to be ∼4.2 × 106, while the energy detection limit was ∼160 aJ per pulse within a 15-ps gating pulse.