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Free-space electro-optic (EO) modulators operating at gigahertz and beyond are attractive for a wide range of emerging applications, including high-speed imaging, free-space optical communication, microwave photonics, and diffractive computing. Here, we experimentally demonstrate a high-speed plasmonic metasurface EO modulator operating in a near-infrared wavelength range with a gigahertz modulation bandwidth. To achieve efficient intensity modulation of reflected light from an ultrathin metasurface layer, we utilize the bimodal plasmonic resonance inside a subwavelength metal–insulator–metal grating, which is precisely tuned to satisfy the critical coupling condition. As a result, perfect absorption of −27 dB (99.8%) and a high quality (Q) factor of 113 are obtained at a resonant wavelength of 1650 nm. By incorporating an EO polymer inside the grating, we achieve a modulation depth of up to 9.5 dB under an applied voltage of ±30 V. The 3-dB modulation bandwidth is confirmed to be 1.25 GHz, which is primarily limited by the undesired contact resistance and the output impedance of the driver. Owing to the high electrical conductivity of metallic gratings and a compact device structure with a minimal parasitic capacitance, the demonstrated device can potentially operate at several tens of gigahertz, which opens up exciting opportunities for ultrahigh-speed active metasurface devices in various applications.

The optical-phased array (OPA) has gained special interest in recent years as a high-speed and compact imaging device. While large-scale OPAs have been demonstrated in single-pixel imaging, the complexity of the driver circuit is becoming a crucial problem as the number of phase shifters increases. Here, we investigate the phase shift requirement of OPA for single-pixel imaging and demonstrate, for the first time, that full 2π phase shifts are not mandatory to generate a set of illumination patterns with a sufficient degree of randomness required to reconstruct the image. Using a silicon photonic OPA chip with 128 carrier-depletion-based phase shifters, we experimentally confirm this property by successfully retrieving an image under a maximum phase shift of only ∼1.5π without affecting the quality of the image. Consequently, the input voltage can be reduced significantly. Since the carrier-depletion phase shifters generally require high driving voltages, this finding paves the way to high-speed OPA-based imaging with a minimum device requirement.

Orbital-angular-momentum (OAM) beams have great potential for multiplexing signals in optical communication, but creating a compact source is challenging. The authors integrate a chip-scale optical vortex emitter and DFB laser into a single monolithic device for direct electrically pumped production of OAM beams.

An InP/InGaAsP integrated 1 times 8 optical phased-array switch is designed, fabricated, and characterized for high-throughput broadband wavelength-division multiplexed (WDM) optical packet switching application. With a single stage of phase shifters utilizing carrier-induced refractive index change, switching to the eight output ports is demonstrated successfully. The polarization-dependent loss is 2.2 dB in the worst case, and the wavelength-dependent loss is less than 2.5 dB across the entire C-band (1520-1580 nm) with the average extinction ratio of 17.7 dB. The measured reconfiguration time is shorter than 6 ns. Low-penalty transmission of a 40-Gb/s non-return-to-zero signal is also demonstrated for the first time. These features make the integrated phased-array switch an attractive candidate to be deployed in the future high-capacity optical packet switching networks.