Zero-order suppression for two-photon holographic excitation

Oscar Hernandez (1) , Marc Guillon (2) , Eirini Papagiakoumou (2) , Valentina Emiliani (2)

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
2 UMR 8250 - Laboratoire de Neurophotonique

Wavefront shaping with liquid-crystal spatial light modulators (LC-SLMs) is frequently hindered by a remaining fraction of undiffracted light, the so-called "zero-order." This contribution is all the more detrimental in configurations for which the LC-SLM is Fourier conjugated to a sample by a lens, because in these cases this undiffracted light produces a diffraction-limited spot at the image focal plane. In this Letter we propose to minimize two-photon (2P) excitation of the sample, resulting from this unmodulated light, by introducing optical aberrations to the ex-citation beam. Aberrations are subsequently compensated by the LC-SLM, but only for the modulated part of the beam, and not for the zero-order component. In order to experimentally demonstrate the method, we use astigmatism as the optical aberration, by simply adding one or two cylindrical lenses in the optical path of the beam. A 10 4 decrease in zero-order-induced 2P fluorescence intensity is demonstrated. Combining this approach with temporal focusing is shown to decrease zero-order fluorescence by a factor of 4 · 10 6.

Domaines: Physique [physics]; Science non linéaire [physics]

Oscar Hernandez, Marc Guillon, Eirini Papagiakoumou, Valentina Emiliani. Zero-order suppression for two-photon holographic excitation. Optics Letters, 2014, 39 (20), pp.5953. ⟨10.1364/ol.39.005953⟩. ⟨hal-01963750⟩