I am going to work with two-photon microscopy at low intensities (~0.5 W/cm^2 per pulse on sample) with 160 fs pulses @950 nm.
I'm looking for sensitive probes capable of showing two-photon fluorescence even in this regime, like quantum dots or upconversion nanoparticles.
The probes should be at most 1 um in size, though I suppose this is quite common.
What would be the best option in your opinion?