Optoelectronic terahertz modulators, operating by actively tuning metamaterial, plasmonic resonator structures, have helped to unlock a myriad of terahertz applications, ranging from spectroscopy and imaging to communications. At the same time, due to the inherently versatile dispersion properties of metamaterials, they offer unique platforms for studying intriguing phenomena such as negative refractive index and slow light. Active resonance frequency tuning of a metamaterial working in the terahertz regime is achieved by integrating metal coupled resonator arrays with electrically tunable graphene. This metamaterial device exploits coupled plasmonic resonators to exhibit an electromagnetically induced transparency analog, resulting in the splitting of the resonance into coupled hybrid optical modes. By variably dampening one of the resonators using graphene, the coupling condition is electrically modulated and continuous tuning of the metamaterial resonance frequency is achieved. This device, operating

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We present a fast room-temperature terahertz detector based on interdigitated bow-tie antennas contacting graphene. Highly efficient photodetection was achieved by using two metals with different work functions as the arms of a bow-tie antenna contacting graphene. Arrays of the bow-ties were fabricated in order to enhance the responsivity and coupling of the incoming light to the detector, realizing an efficient imaging system. The device has been characterized and tested with a terahertz quantum cascade laser emitting in single frequency around 2 THz, yielding a responsivity of ∼34 μA/W and a noiseequivalent power of ∼1.5 × 10 −7 W/Hz 1/2 .

Terahertz (0.1-10 THz corresponding to vacuum wavelengths between 30 μm and 3 mm) research has experienced impressive progress in the last few decades. The importance of this frequency range stems from unique applications in several fields, including spectroscopy, communications, and imaging. THz emitters have experienced great development recently with the advent of the quantum cascade laser, the improvement in the frequency range covered by electronic-based sources, and the increased performance and versatility of time domain spectroscopic systems based on full-spectrum lasers. However, the lack of suitable active optoelectronic devices has hindered the ability of THz technologies to fulfill their potential. The high demand for fast, efficient integrated optical components, such as amplitude, frequency, and polarization modulators, is driving one of the most challenging research areas in photonics. This is partly due to the inherent difficulties in using conventional integrated modulation techniques. This article aims to provide an overview of the different approaches and techniques recently employed in order to overcome this bottleneck.

Abstract:We present the first quantum key distribution (QKD) experiment over multicore fiber. With space division multiplexing, we demonstrate that weak QKD signals can coexist with classical data signals launched at full power in a 53 km 7-core fiber, while showing negligible degradation in performance. Based on a characterization of intercore crosstalk, we perform additional simulations highlighting that classical data bandwidths beyond 1Tb/s can be supported with high speed QKD on the same fiber. References and links