Characterization of Orbital Angular Momentum Quantum States Empowered by Metasurfaces

Abstract

Twisted photons can in principle carry a discrete unbounded amount of orbital angular momentum (OAM), which are of great significance for quantum communication and fundamental tests of quantum theory. However, the methods for characterization of the OAM quantum states present a fundamental limit for miniaturization. Metasurfaces can exploit new degrees of freedom to manipulate optical fields beyond the capabilities of bulk optics, opening a broad range of novel and superior applications in quantum photonics. Here we present a scheme to reconstruct the density matrix of the OAM quantum states of single photons with all-dielectric metasurfaces composed of birefringent meta-atoms. We have also measured the Schmidt number of the OAM entanglement by the multiplexing of multiple degrees of freedom. Our work represents a step toward the practical application of quantum metadevices for the measurement of OAM quantum states in free-space quantum imaging and communications.

Ultrafast all-optical second harmonic wavefront shaping

“…More details can be found in the section “Design principle of the metasurfaces” in the Supplementary Information. All three types of metasurfaces were fabricated on a glass substrate using electron-beam lithography and inductively coupled plasma etching using an established process 42 . For each of the three targeted wavefront shaping effects, a separate metasurface with its own unique geometry and corresponding spatially variant phase profiles was fabricated.…”

Nonlinear chiral metaphotonics: a perspective

“…Last year, dielectric metasurfaces pumped with circularly polarized light were used for characterization of the orbital angular momentum of quantum states in the SPDC process. 19 Another very recent study demonstrated optical spin-orbit interaction in the SPDC process realized through a nonlinear crystal with threefold rotational symmetry. 100 Following these studies, we foresee a variety of theoretical and experimental studies of chirality in quantum light interaction with metastructures empowered by optical resonances.…”

“…12,13 In particular, very recently planar dielectric metastructures hosting photonic Mie resonances were shown to enhance the local chirality density and provide selective coupling to left-circularly polarized (LCP) and right-circularly polarized (RCP) waves. 14,15 This led to far-reaching implications for chiral emission, 16 chiral sensing, 17,18 characterization of quantum light, 19 and other areas.…”

The transport properties of vortex pair with opposite sign and application to optical field focusing

“…Vortex beams have been widely studied in the fields of communications [1], imaging [2], optical tweezers [3], and quantum information [4] because they carry orbital angular momentum. The magnitude of orbital angular momentum as a physical quantity is numerically equivalent to the topological charge of the vortex beam, and the value of the topological charge can be easily obtained directly from the optical field phase.…”