WP1
WRC has studied various dielectric media for the generation of the electric currents that results from the transient semimetallization. A test beamline for optoelectronic components based on the transient semimetallization has been achieved.
CEA has focused on GaN semiconductor which HHG polarization response indicates strong symmetry dependence, a promising route towards petahertz symmetry gating controlled using two colour few optical cycle mid-infrared pulses with attosecond delay and CEP stability.
FAU has demonstrated charge transfer from graphene towards silicon carbide within 300as, which is the fastest charge transfer measured from one material to another. Moreover, they have investigated the temporal evolution of electron dynamics in 2D materials and found that for 2D materials with a hexagonal lattice and broken inversion symmetry an increase of the waveform-dependent residual current is expected.
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 tunnelling into vacuum, and magnifying nanoscale geometrical information from the tip apex to a macroscopic scale.
CEA and XLIM have investigated the possibility of creating petahertz switches in VO2 and NbO2, two materials exhibiting ultrafast femtosecond phase transition from insulator to metallic states.
WP2
WRC has demonstrated a waveguide exhibiting large fields with short temporal duration at the desired location due to its broadband coupling capabilities, a crucial component of any PHz device.
LMU has work to advance the metrology of petahertz electronics, pushing the controllability of field waveforms used in switching and developing a nanoscale field sampling technology to characterize those laser pulses.
ICFO has investigated with a first attosecond and state-resolved measurement the carrier-band dynamics in the quantum material semi-metal TiS2, interesting for ultrafast optoelectronic devices and field-effect transistors.
CEA and MPSD have validated a time dependent density functional theory code. Simulations have demonstrated 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.
CEA had faced hurdles while trying to implement a EUV spectral phase measurement experiment based on the RABBITT technique to characterize the petahertz currents. Despite many efforts, the electron spectrometer is not yet functioning. However, efforts are continuing beyond the end of PETACOM project.
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. Novae, XLIM and MENLO System were able to deliver a 100MHz CEP stable laser system, providing sub-30fs pulse with 1W power and a spectrum centred at 1550nm. The system was installed at FAU, and is now available for experiments.
A second system, designed and fabricated at XLIM, provides fs pulses in the mid infrared region, as shifting the spectrum towards larger wavelength is beneficial for petahertz optoelectronics. It delivers 180fs pulses at a repetition rate of 1MHz, with a pulse energy of 50nJ and a central wavelength of 4520nm. Despite the low energy per pulse, the strong field regime needed to control electron current is reached, as demonstrated by an all fibre based high order harmonic source implemented on this laser.
WP4
We developed two different strategies to efficiently couple ultrashort light pulses to the active material of an opto-electronic device. A conical shape dielectric optical waveguide allows increasing by one order of magnitude the laser field intensity locally, which releases the constraints on the laser performances. The strong field regime was reached by confining the electric field in a single 3D ZnO semiconductor waveguide. The second strategy relies on surface plasmon polariton launched several 10s of μm away from the active part on specific waveguides. Here, the coupling structure between the laser field and the SPP has been optimized to allow sub 10 fs SPP. Field enhancement has been studied to lower the requirement on the laser parameter for future integration.
Within PETACOM, we were able to demonstrate several high-speed opto-electronic devices where current generation and control is obtained from strong ultrashort laser fields. Apart from attosecond control of the current, we demonstrated light induced ultrafast gating, ultrafast Schottky diodes and CEP control logic gates.
WP5
All the results were published in high impact international scientific journals and presented at international conferences. Additionally, patents were submitted and obtained. One technological advance by the project is now a commercial product.
