Abstract
Terahertz sources and detectors have enabled numerous new applications from medical to communications. Yet, most efficient terahertz detection schemes rely on complex free-space optics and typically require high-power lasers as local oscillators. Here, we demonstrate a fiber-coupled, monolithic plasmonic terahertz field detector on a silicon-photonics platform featuring a detection bandwidth of 2.5 THz with a 65 dB dynamical range. The terahertz wave is measured through its nonlinear mixing with an optical probe pulse with an average power of only 63 nW. The high efficiency of the scheme relies on the extreme confinement of the terahertz field to a small volume of 10−8(λTHz/2)3. Additionally, on-chip guided plasmonic probe beams sample the terahertz signal efficiently in this volume. The approach results in an extremely short interaction length of only 5 μm, which eliminates the need for phase matching and shows the highest conversion efficiency per unit length up to date.
Highlights
Terahertz sources and detectors have enabled numerous new applications from medical to communications
The nonlinear mixing with the probe pulse typically occurs in exotic material systems, such as e.g. zinc-telluride (ZnTe)[11] or gallium arsenide (GaAs)[12], and a high sensitivity is only reached at the expense of a high laser power[13]
Photoconductive antennas (PCA) produced on low-temperature grown GaAs (LT-GaAs)[12] or indium gallium arsenide (InGaAs)[18] substrates are relatively compact and have already demonstrated high sensitivities when integrated with plasmonic electrodes[19]
Summary
Terahertz sources and detectors have enabled numerous new applications from medical to communications. Photoconductive antennas (PCA) produced on low-temperature grown GaAs (LT-GaAs)[12] or indium gallium arsenide (InGaAs)[18] substrates are relatively compact and have already demonstrated high sensitivities when integrated with plasmonic electrodes[19] While these detectors feature a broad bandwidth and a very high dynamical range at short measurement acquisition times, a fine balance has to be found between the carrier mobility and lifetime to ensure an efficient yet broadband detection[20]. Integrated plasmonic waveguides[27] functionalized with nonlinear materials have shown impressive nonlinear χ(2) efficiencies[28] They have demonstrated good performance as electro-optical modulators for high-bit rate systems up to 120 GBd29 or for the direct electro-optical up-conversion of 60 GHz microwave signals[30,31].
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