Imaging the Gouy phase shift in photonic jets with a wavefront sensor

Awavefront sensor is used as a direct observation tool to image the Gouy phase shift in photonic nanojets created by micrometer-sized dielectric spheres. The amplitude and phase distributions of light are found in good agreement with a rigorous electromagnetic computation. Interestingly the observed phase shift when travelling through the photonic jet is a combination of the awaited π Gouy shift and a phase shift induced by the bead refraction. Such direct spatial phase shift observation using wavefront sensors would find applications in microscopy, diffractive optics, optical trapping, and point spread function engineering. © 2012 Optical Society of America OCIS codes: 120.5050, 050.5080, 110.7348. The Gouy phase has been puzzling physicists since its dis-covery in 1890 byGouy [1]. It relies on an extra phase con-tribution ϕG to the propagating phase kz (k being the wavevector and z the distance) a beam experiences when it travels through its focus. TheGouy phase is important in physical optics since it explains the phase advance postu-lated by Fresnel for the secondary Huygens wavelets cre-ated from a primary wavefront in the wave diffractio