Silicon–plasmonic integrated circuits for terahertz signal generation and coherent detection

Abstract

Optoelectronic signal processing offers great potential for generation and detection of ultra-broadband waveforms in the THz range, so-called T-waves. However, fabrication of the underlying high-speed photodiodes and photoconductors still relies on complex processes using dedicated III-V semiconductor substrates. This severely limits the application potential of current T-wave transmitters and receivers, in particular when it comes to highly integrated systems that combine photonic signal processing with optoelectronic conversion to THz frequencies. In this paper, we demonstrate that these limitations can be overcome by plasmonic internal photoemission detectors (PIPED). PIPED can be realized on the silicon photonic platform and hence allow to leverage the enormous opportunities of the associated device portfolio. In our experiments, we demonstrate both T-wave signal generation and coherent detection at frequencies of up to 1 THz. To proof the viability of our concept, we monolithically integrate a PIPED transmitter and a PIPED receiver on a common silicon photonic chip and use them for measuring the complex transfer impedance of an integrated T-wave device.Terahertz signals (T-waves) offer promising perspectives for a wide variety of applications, comprising high-speed communications 1-3 , microwave photonics 4 , spectroscopy 5,6 , life sciences 7,8 , as well as industrial metrology 9,10 . Optoelectronic signal processing techniques are particularly attractive both for T-wave generation 1,11,12 and detection [13][14][15] , especially when broadband operation is required. On a conceptual level, optoelectronic T-wave generation relies on mixing of two optical signals oscillating at frequencies and b f in a high-speed photodetector, for which the photocurrent depends on the incident optical power 11 . The photocurrent oscillates with a difference frequency THz   Rx,1 U t modulates the device sensitivity. The PIPED photocurrent is then given by the product of the time-variant sensitivity with the time-variant optical power   Rx P t .

Key Roles of Plasmonics in Wireless THz Nanocommunications—A Survey

“…Alternatively, plasmonic internal photoemission detectors (PIPED) structures, which are actually transmitter and receiver packages, monolithically integrated on a common silicon photonic chip platform, have been also proposed in [157], for THz wave signal generation and coherent detection at frequencies of up to 1 THz. Finally, other more novel approaches are related to the employment of a FET operating at THz frequencies (TeraFET), as a THz detector.…”

Efficient Surface Plasmon Polariton Excitation and Control over Outcoupling Mechanisms in Metal–Insulator–Metal Tunneling Junctions

“…SPPs are typically excited with bulky light sources that are too large for nano‐circuitry integration; hence, for many applications it would be desirable to have access to footprint‐compatible electrically driven SPP sources. Metal–insulator–metal tunneling junctions (MIM‐TJs) are known to electrically excite SPPs and photons via inelastic tunneling under an applied bias14–17 ( Figure a) and are therefore interesting candidates 18–20. Until recently, prohibitively low electron‐to‐photon conversion efficiency (10 4 –10 7 electrons result in a single photon14–16,21–23) due to the large momentum mismatch between the initially excited MIM‐TJ cavity mode (MIM‐SPP) and the radiating mode, coupled with an inelastic tunneling event probability of 10%,24 has prevented practical applications of MIM‐TJs.…”

All-dielectric concentration of electromagnetic fields at the nanoscale: the role of photonic nanojets

“…Without any doubt, the research on plasmon-assisted concentration of light into nanoscale volumes will remain as one of the hot elds (along with metamaterials) because of its revolutionary potentials in many elds like microscopy, 3 sensing, 4,5 and integrated circuits. 6 By propagating a mid-IR surface wave along a tapered two-wire transmission line, nanoscale IR spot with a diameter of 60 nm (l/150) was observed using a neareld microscope. 7 Nanoscale focusing with a 2 Â 5 nm 2 footprint and an intensity enhancement of 3.0 Â 10 4 was achieved in an Au-SiO 2 -Au gap plasmon waveguide using a carefully engineered threedimensional taper.…”