Metalasers with arbitrarily shaped wavefront

Integrated nanolasers have been explored for decades owing to their important role in many applications, ranging from optical information processing and communications to medical treatments^1-6. Although polarization, orbital angular momentum and directivity of nanolasers have been successfully manipulated^7-9, neither their laser wavefront nor radiation characteristics can be customized at will. More optical elements are often required to further modify the laser characteristics, making the lasing system bulky and restricted by inevitable speckle noise. Here we suggest and realize a new type of laser, a metalaser, by using the interplay between local and nonlocal responses of dielectric resonant metasurfaces. The lasing mode is confined by nonlocal interaction between meta-atoms of a planar structure and the beam wavefront is precisely shaped by locally varying dipole momenta. Consequently, the metalaser emission can directly have any desired profile, including focal spots, focal lines, vector beams, vortex beams and even holograms. Notably, the scattered waves of the metalaser do not undergo resonant amplification like laser modes, being orders of magnitude weaker. As a consequence, the speckle noise becomes negligibly small in our metalaser holograms, providing a viable solution to the speckle noise problem of conventional laser holograms. This finding enriches our understanding of lasers and promotes their performance for various optical and photonic applications.