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Petahertz Quantum Optoelectronic Communication

Periodic Reporting for period 2 - PETACom (Petahertz Quantum Optoelectronic Communication)

Periodo di rendicontazione: 2020-03-01 al 2021-08-31

The PETACom project proposes to create future optoelectronic device commutating at petahertz frequencies, bridging the gap between electronics and photonics. We aim to realize future electronic devices controlled by ultrafast intense laser pulses that will oscillate 1000 faster than today's fastest transistors. Within PetaCOM, we aim to establish: 1) Petahertz electron switching in 2D and 3D systems using intense femtosecond IR to mid-IR laser excitation. 2) Optoelectronic devices from laser induced petahertz electron oscillation. 3) A new paradigm for future electronics and ultrahigh speed communication and computation.
WP1
WRC is investigating various dielectric media and the generation of the electric currents that results from the transient semimetallization and to achieve control over the direction of the generated currents. A test beamline for optoelectronic components based on the transient semimetallization has been achieved.

Petahertz symmetry gating in semiconductors: At CEA, we have started to focus on GaN semiconductor which HHG polarization response indicates strong symmetry dependence on harmonics 5th and 7th. We expect petahertz electron bursts control using two colour few optical cycles mid-infrared pulses with attosecond delay and CEP stability.

FAU hase demonstrated charge transfer from graphene towards Silicon carbide within 300±200 attoseconds, which is the fastest charge transfer measured from one material to another [C. Heide et al. Nat. Photonics (2020). https://doi.org/10.1038/s41566-019-0580-6]. This results has been highlighted for the Nature Photonics cover, Volume 14 Issue 4, April 2020.

FAU has theoretically investigated the temporal evolution of electron dynamics in 2D materials, such as in graphene or MoS2. We found that for 2D materials with a hexagonal lattice and broken inversion symmetry an increase of the waveform-dependent residual current is expected [C. Heide et al., JPhys Photonics 2 024004 (2020)].
LMU has used field-emission microscopy to observe single fullerene molecules deposited on a tungsten nano-tip apex. Applying strong electric fields to a metallic nano-tip enables a field emission due to the electrons tunneling into vacuum, and magnifying nanoscale geometrical information from the tip apex to a macroscopic scale. By depositing fullerene molecules on a tungsten nano-tip and applying strong DC fields, field emission can be driven from individual molecules.

CEA and XLIM have investigated the possibility of creating petahertz switches in VO2. However, thermal issues and the long multicycle regime prevent to observe relevant dynamics. To solve the thermal issue, we propose to use NbO2, which has a much higher damage threshold and insulator to metal transition temperature.

WP2
WRC has performed simulations to optimize the parameters of a coupling and waveguiding element exhibiting i) large fields at the desired location with ii) short temporal duration due to the broadbandcoupling. As a next step, fabrication and probing of these elements will be carried out for nanoscale integration of PHz electronic devices.

At LMU we have recently reviewed our perspective on petahertz electronics. To advance the metrology of petahertz electronics, we have pushed the controllability of field waveforms used in switching (by development of a broadband field synthesizer), and are exploring the possibility to implement nanoscale field sampling.
ICFO has investigated with a first attosecond and state-resolved measurement the carrier-band dynamics in the quantum material TiS2. TiS2, is a semi-metal. This material interesting for ultrafast optoelectronic devices and field-effect transistors, for solid batteries and high-density energy storage.

CEA is setting a full characterization of the electron trajectory in the crystal conduction band. This information can be extracted from the HHG spectral phase accessible using the RABBIT technique. We are actually extending the EUV RABBIT technology (limited to 12 . eV lower energy) to the UV (down to 4 eV) using alkali metals such as potassium (Ip=4.34eV). We plan to resolve the electron dynamic involved in low and high band gap semiconductors. This knowledge is relevant for applications of attosecond pulses e.g. for the metrology of optoelectronic switches operating in the petahertz regime

CEA and MPSD have validated a time dependent density functional theory (TD-DFT) code. Simulation shave been performed on graphene, silicon, GaAs and more recently on MgO to operate an attosecond gating technique using a two-color few optical cycles scheme. The tool is available to further interpret and guide the PETACom research on various 2D and bulk semiconductors and dielectrics.

WP3
The discussion with the project partners has shown that it would be beneficial for the project progress to have a low-repetition rate CEP stable system with few-cycle pulse durations available before moving to the GHz repetition rate. Therefore, the work package concerning the generation of few-cycle pulses was swapped with the work package concerning GHz repetition rates and amplification to 10W average power.

A second system, designed and fabricated at XLIM, provides 80 fs pulses at 2900 nm (Delahaye2019). Further work is ongoing to compress those pulses down to 20 fs, thus providing 2-cycle pulses with nanojoule pulse energy to PETACom partners next year.

WP4
Field enhancement has been studied to lower the requirement on the laser parameter for future integration. The strong field regime is reached by confining the electric field from a few nanojoules femtosecond laser in a single 3D ZnO semiconductor waveguide
WP5
Dissemination is published at www.petacom.fr.
WP1
What brings us beyond the state of the art is the low pulse energy we plan to use to induce the semi-metallization using nano-architectures that could enhance the current due to plasmonic or field enhancement effects. technology. Recent simulations indicate that materials with a higher non-linearity are better candidates for petahertz commutation.

WP2
FAU is now measuring CEP-dependent current across the graphene/SiC Schottky junction. We have new results from tungsten tips that yield deep insights into the attosecond electron dynamics at tungsten needle tips.
LMU has realized ultrafast devices based on 2D materials and advanced metrology of petahertz electronics by controlled waveforms and nanoscale field sampling.

WRC- A broadband coupler can serve as a building block of a future ultrafast signal processing device.

CEA and MPSD have performed simulation of bulk MgO excited by two laser fields of different frequencies. Our results demonstrate a very strong anisotropy and the generation of isolated attosecond light pulses which reflects the petahertz electron current switching.

WP3
A second system, designed and fabricated at XLIM, provides 80 fs pulses at 2900 nm (Delahaye2019). Further work is ongoing to compress those pulses down to 20 fs, thus providing 2-cycle pulses with nanojoule pulse energy to PETACom partners next year.
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