Researchers at the Freie Universität Berlin have published “Polarization enhanced two-photon excited fluorescence contrast by shaped laser pulses using a deformable phase plate” in Applied Optics (Vol. 62, No. 31). The study uses laser pulses shaped in space and in time to raise the fluorescence contrast between dyes — and the spatial shaping is done with a Delta 7.
Why a refractive modulator
The contrast between two dyes can be enhanced by shaping the exciting pulse differently in perpendicular polarization directions. A liquid-crystal modulator acts on one polarization; the Deformable Phase Plate modulates the wavefront in all polarization directions, which is what made the scheme practical. The gain matters most where contrast is hardest to come by: deep in tissue, and in three-dimensional scanning of probes.
For the Delta 7 it is a use beyond aberration correction — shaping the beam rather than cleaning it up.
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