A publication just appeared on Optics Express as a result of the research ongoing at the Polimi and UNIMIB groups.

High dioptric power micro-lenses fabricated by two-photon polymerization. Behjat S. Kariman, Alessandra Nardini, Mario Marini, Pablo Roldán-Varona, Claudio Conci, Manuela T. Raimondi, Roberto Osellame, Giulio Cerullo, Giuseppe Chirico, and Rebeca Martínez Vázquez. Opt. Express 32(27), 48114-48131 (2024)

We design, fabricate, and test a single micro-optical element with high dioptric power and high NA (up to 1.25 in water). The dioptric power and magnification of the microlenses were quantified over a 200 × 200 µm aberration-free field of view. Our results indicate that these microlenses can be used for wide-field imaging under linear excitation and have the optical quality to be utilized for nonlinear excitation imaging. Moreover, being made of biocompatible photoresist, they can be implanted close to the observation volume and help to reduce the spherical aberration of laser beams penetrating living tissues.

Wide-field images of Nile red fluorescent beads and Convallaria Majalis using parabolic microlenses (Ø=600 µm, fn = 350 µm)coupledtoawide-fieldopticalmicroscope. Images are obtained under green excitation and epifluorescence detection. (a) Control widef ield image of the beads when the objective focal plane is set to the glass coverslip. In this condition the beads outside the lens FOV (in the upper right-hand area) are imaged in-focus by the objective alone, whereas through the lens the beads appear out-of-focus (central area). (b) a close-up of the region highlighted in red in (a). (c) Wide-field image of the beads collected in-focus through the microlens. (d) Close-up of the region marked in red in (c), where a total magnification equal to 38X has been achieved. (e, f) Wide-field images of Convallaria Majalis under green excitation. (e) Epifluorescence image obtained while focused on Convallaria out of the lens. The central circular signal corresponds to the out-of-focus signal collected by the microlens. (f) Wide-field image collected through microlenses.