The capability of locally engineering the nonlinear optical properties of media is crucial in nonlinear optics. Although poling is the most widely employed technique for achieving locally controlled nonlinearity, it leads only to a binary nonlinear state, which is equivalent to a discrete phase change of π in the nonlinear polarizability. Here, inspired by the concept of spin-rotation coupling, we experimentally demonstrate nonlinear metasurfaces with homogeneous linear optical properties but spatially varying effective nonlinear polarizability with continuously controllable phase. The continuous phase control over the local nonlinearity is demonstrated for second and third harmonic generation by using nonlinear metasurfaces consisting of nanoantennas of C3 and C4 rotational symmetries, respectively. The continuous phase engineering of the effective nonlinear polarizability enables complete control over the propagation of harmonic generation signals. Therefore, this method seamlessly combines the generation and manipulation of harmonic waves, paving the way for highly compact nonlinear nanophotonic devices.

We experimentally demonstrate dramatically enhanced light-matter interaction for molecules placed inside the nanometer scale gap of a plasmonic waveguide. We observe spontaneous emission rate enhancements of up to about 60 times due to strong optical localization in two dimensions. This rate enhancement is a nonresonant nature of the plasmonic waveguide under study overcoming the fundamental bandwidth limitation of conventional devices. Moreover, we show that about 85% of molecular emission couples into the waveguide highlighting the dominance of the nanoscale optical mode in competing with quenching processes. Such optics at molecular length scales paves the way toward integrated on-chip photon source, rapid transfer of quantum information, and efficient light extraction for solid-state-lighting devices.

We demonstrate an all-dielectric quantum electrodynamical nanowire-slab system with a single emitter that concentrates the extremely intense light at the scale of 10 × 75 nm(2). The quantum dot exhibits a record high 31-fold spontaneous decay rate enhancement, its optical saturation and blinking are strongly suppressed, and 80% of emission couples into a waveguide mode.

Surface plasmon polaritons (SPPs) have shown high potential for various applications in various fields, ranging from physics, chemistry, and biology to integrated photonic circuits due to their the strong confinement of light to the metal surface. Exciting an SPP from a free-space photon in a controllable manner is an essential step toward more complex and integrated applications. Methods for coupling photons to SPPs are numerous, but in order to control the amplitude and phase of an SPP, most of these methods require bulky or multiple optical components or sensitive adjustments that are difficult to control. Here we present a novel approach for an independent control of the amplitude and phase of an SPP excited by a normally incident beam using a metasurface. The full control in amplitude and phase is achieved via the polarization state and polarization orientation angle of the electrical field of the incoming light. We experimentally demonstrate the functionality of such a metasurface consisting of periodic nanoantennas for the excitation of SPPs at a metal–dielectric interface. Our approach opens up new ways for coherently controllable integrated plasmonic circuits that can be used in conjunction with fast dynamic polarization modulation techniques.