Development of photonic architecture of M-ENGINE modules to meet the required KPIs: The M-ENGINE partners have drafted a system architecture based on the evaluation of industrial foundry capabilities and component performance. In particular, the foundry platform provides the photonic basis for the module: the SiN propagation loss dictates the maximum achievable quality factor (Q-factor), and hence, requisite laser pump power for comb generation. The consortium explored various mitigation and compensation strategies for vertical misalignment and also developed an approach enabling evanescent coupling of SOAs for amplification, post-comb generation. Additionally, close collaboration with X-Celeprint during this evaluation and design process enabled the inclusion of MTP design considerations from the outset.
Development of high-power distributed feedback lasers for transfer printing: In year 1 we completed a fabrication run of high-power DFB lasers which involved epitaxial growth, grating write, waveguide etching, and singulation of the lasers based on traditional cleaving techniques with a portion of the wafer reserved for dry etching of the facets to allow a comparison study between both techniques. Etching the facets & wafer level coating is a key step in moving from individual cleaved lasers to wafer-level processing and MTP. Additionally, we have a design in place to include the requisite chip modifications necessary for flip-chip transfer printing, i.e. top side P/N electrical contacts, etched facets, alignment fiducials and inclusion of the release layer in the epi stack to enable MTP of the laser.
Development of full wafer-scale transfer printing: The consortium has developed an epitaxial design which includes X-Celeprint’s release layer, i.e. 500nm AlInAs. The position of the release layer is critical to ensure optimal alignment of the laser mode with the SiN waveguide mode and Enlightra have provided the required thickness for the n-cladding of the InP chip allowing an epitaxial growth run to commence in Q1 2025.
Design of optimized nanostructured photonic microresonator: DESY and ICB reported the initial safe design of the microresonator, including the mask layout for chip- and wafer-level fabrication, following the PDK rules of the fabrication provider LIGENTEC. The design is based on numerical simulations and published experimental results. This base design aims to guarantee minimum performance in frequency comb generation as part of the laser co-integration development aspect of the project, in order to de-risk this stage of technological development.
DESY, with input from M-ENGINE partners, has developed a new design for PhCR structures that includes complex corrugation patterns. The aim of these structures is to test output comb spectrum shaping. ICB has developed ring and PhCR structures for a new 350 nm silicon nitride thickness platform provided by LIGENTEC (AN350).
Testbench development and peformance testing. A testbench has been developed that can characterise the main parameters of the M-Engine devices including basic spectral output, output power per carrier, relative intensity noise (RIN) and phase noise of the comb lines, and phase correlation between the comb lines. Initial testing has been carried out using a benchtop Kerr comb source from Enlightra. A system evaluation testbed has also been developed to operate in the C Band (1530 to 1570nm) with an intensity modulation / direct detection system operating at baud rates upto 100 Gbaud with OOK and PAM4 modulation formats.
