During the first periodic reporting period (M1-18), and in accordance to the Grant Agreement (GA), the overall design of the two demonstrators, namely the quantum sensor (WP15) and the photonics qubit generator (WP14) have been realized (D15.1) allowing for the flow down of requirements for the different complex quantum PICs building blocks developed in the different WPs, namely the multiwavelength tunable laser (WP10), the light conditioning circuit (WP12), the ion-trap PIC (WP13), the UVC light source (W11, D11.1) and the modulators/phase shifters (WP4).
Further flow down of the requirements from the complex PIC building blocks to the individual simple PIC building blocks was also realized, providing all partners in the project with specs to start the development of the different technological building blocks. TU Berlin has started the development of a UVC gain material based on AlGaN strained multiple quantum wells, with preliminary optical gain and lasing in optically pumped gain sections. To allow for micro transfer printing (TP) of the UVC gain sections developed by TU Berlin, Chalmers has started the development of an optoelectrochemical underetching technique to remove a sacrificial layer that will permit preparing the coupons for TP and UGent has demonstrated preliminary transfer (WP8) of the coupons underetched using this technique. The gain material for the multiwavelength laser in WP10 have been procured by TOPTICA and characterized to ensure performance complying with the specifications. Several simple building blocks (i.e. waveguides, edge couplers, bent waveguides, directional couplers, Y-splitters, and MMIs (1x2 and 2x2) have been designed by VLC Photonics. After validation of the performance of the building blocks, they will be introduced in a PDK of quantum building blocks (WP9). The simple building blocks have been combined by PTB to design the passive cavities for the multiwavelength laser (WP10) and the external cavity laser at 280 nm (WP11). The different building blocks have been submitted to ALUVIA for fabrication.
The design of superconducting nanowire detectors integrated on top of Al2O3 waveguide has started (WP3). WWU has performed an optimization study of the cross-section of the waveguide to permit coupling of photons from the waveguide to the superconducting nanowires for efficient detection. WWU has worked in close collaboration with ALUVIA for the realization of preliminary tests with Al2O3 waveguides. A process flow and waveguide geometry has been designed and will be fabricated in the next reporting period. WWU and UTwente have also worked in close interaction to define the requirements for the design of the ASIC to realize the redout from the superconducting nanowire detectors. The device should operate under cryogenic temperature. Active quenching has been identified as the mechanism providing faster response time and the design is ongoing towards a tape-out in October 2025 in the commercially available GlobalFoundries 22nm FDSOI technology. The first concept towards the transfer of power and data to the device placed in cryogenic temperatures has also been proposed by the UTwente based on SOI PIN diodes that are available in the same Globalfoundries 22 nm FDSOI technology.
Fast, power-efficient modulators integrated on the Al2O3 platform are another of the key building blocks that are being developed in QU-PIC and that will be used in the different technology demonstrators. The requirements for the modulators for the atomic sensing demonstrator (D15.1) and for the photonic quantum state generator developed by QUIX have been defined. Both PTB and UTwente have started the design of the modulators building blocks with designs based on Mach Zehnder interferometers and micro-ring resonators being ready to be implemented in the aluminium nitride material that is currently being developed by the UTwente. The development of the aluminium nitride (AlN) material has started at the UTwente, with a first optimization leading to slab propagation losses as low as 4 dB/cm at 633 nm, which leads to below 0.5 dB/cm of slab losses at 1550 nm. Further optimization is possible and will be carried out during the next reporting period while the fabrication of modulator devices in the current layers is on-going with the identified process flow.
