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T-NEXT focused project aims at the development of functional electronic and optical components for free-space optical communications systems in the THz frequency range (1 – 5 THz).

The project activities focus on four main research objectives:

Objective 1. Development of high efficiency THz sources in the 2-5 THz frequency range including miniaturized quantum cascade lasers

Objective 2. Development of Fast and sensitive detectors in the 1-5 THz range including multipixel CMOS based architectures and fast room temperature nanodetectors based on large-area single layer graphene.

Objective 3. Design and development of modulators and metasurfaces for optical beam modulation and shaping.

Objective 4. Study and implementation of integrated systems for a free-space optical communication (FSOC) platform.

T-NEXT is part of Spoke 3 – Wireless Networks and Technologies

O1. Within this objective, the CNR unit has developed THz miniaturized quantum cascade lasers (QCLs) with tailored emission frequencies in the 2-5 THz range, matching the few atmospheric transparency windows (e.g. 3.44 THz). The activity follows two alternative pathways. On one hand, we have developed single-mode THz QCLs with high output power (~ 10 mW). On the other hand, we have demonstrated the possibility of obtaining harmonic frequency combs (HFCs) by engineering the semiconductor lasers waveguide. QCL-based HFCs are THz sources whose spectrum is characterized by few equidistant modes, each carrying optical power > 1 mW. In parallel, we have demonstrated the possibility of real-time measuring the on-chip temperature of THz QCLs by integrating graphene-based thermometers on board to the QCL chip. Calibration of the two set-ups has been carried out in order to compare accuracy and sensitivity

O2. The project simultaneously develops two different technological platforms to devise THz photodetectors: on the one hand devices based on CMOS technology, on the other devices made of graphene. In the first case, UNISAP has implemented a platform (TCAD) for simulating of the rectification effect (self-mixing) inside field effect transistors excited by THz radiation. These preliminary simulations allowed us to establish the optimal geometric parameters for the creation of scalable room temperature photo-detectors that can potentially be integrated into large arrays (target 100x100 pixels). In the second case, the CNR-NANO unit has developed innovative photothermoelectric (PTE) detectors based on large-area, scalable graphene, grown by chemical vapor deposition (CVD). The favorable properties of graphene, such as small electronic heat capacity and ultrafast carrier relaxation dynamics, allow the possibility to simultaneously achieve high sensitivity (noise equivalent power 100 GHz - potential).

O3. In the context of O3, POLIBA and CNR-NANO units have implemented amplitude modulators exploiting graphene/electrolyte gel interfaces, integrated in small reflectarrays. The achieved modulation speed is so far limited to few tens of kHz. However, this activity will be instrumental for the full exploitation of THz frequency carriers that require line-of-sight visibility between transmitters and receivers.

O4. The CNR unit has recently demonstrated a THz free-space optical communication (FSOC) link employing a transportable and cryogen-free setup, which exploits a directly-modulated QCL source at 2.83 THz, hosted in a closed-cycle Stirling cryocooler, and a compact graphene-based PTE detector operating at room temperature. The free-space optical communication link guarantees error-free communication (packet error rate <10-5) over a distance of 128 cm at 1 Mbps (On-Off Keying modulation). The system has been operated outside, to test its performance out of controlled laboratory conditions. Further development on this FSOC platform will be directed to the realization of faster modulation scheme, targeting speeds ~100 MHz.
  • Realization of a fully scalable fabrication protocol for layered material heterostructures based on CVD-grown graphene and hexagonal boron nitride.
  • Realization of graphene photodetectors based on a Salisbury mirror geometry, operating at 3 THz.
  • Realization of an integrated graphene-based thermometer to monitor the temperature of THz QCLs during operation.
  • Development of innovative circuital solutions for the optimal design of a Low Noise Amplifier (LNA) for THz receivers, matching required design specifications in terms of performance parameters, such as peak gain, bandwidth and noise figure, suitable to be applied in the selected receiver scheme developed in T-NEXT. STMicroelectronics and L-foundry companies are at moment both interested to pursue the chip fabrication including antenna array MOSFET THz detector cascaded with the LNA.
  • First demonstration of a cryogen-free portable setup for THz free-space optical communications.
  1. Publications
    • Expected: at least 10 publications on 36 months
    • Accomplished: 1 (2 submitted)
    • Readiness: 10%
  2. Joint Publications
    • Expected: 30% joint publications on 36 months
    • Accomplished: 0 over 1
    • Readiness: 0%
  3. Talks/Communication events
    • Expected: 10 talks or event chairing/organizing within T-NEXT activities on 36 months
    • Accomplished: 4 (among dissemination events and conference presentations)
    • Readiness: >40%
  4. Demo/PoC
    • Expected: 1 PoCs expected by the end of the project
    • Accomplished: 0
    • Readiness: 0% (work according to plan)
  5. Project Meetings
    • Expected: > 18 meetings
    • Accomplished: 5 meetings
    • Readiness: 28%
  6. Patents/Innovations
    • Expected: 1 items over 36 months
    • Accomplished: 0
    • Readiness: 0%
MS0.1 Internal communication tools (M03)
MS0.2 Definition of the scientific content of the cascade calls (M03)
• Expected: 2
• Accomplished: 2
• Readiness: 100%

Project PI: Miriam Serena Vitiello

Collaboration proposals
The T-NEXT Project is open to collaborations on the following topics:

  • THz photodetectors
  • Far-infrared modulation schemes
  • Development of communication protocols based on THz building blocks.

For any proposal of collaboration within the project please contact the project PI.