GOSPEL - Ultra-Broadband Waveform Generation Using Actively Stabilized Hybrid Photonic-Electronic Circuits

GOSPEL aims at exploring, implementing, and demonstrating novel concepts for ultra-broadband photonic-electronic waveform generation that can overcome the limitations of current digital-to-analogue converters (DAC). The concept exploits spectral interleaving of optical waveforms that are modulated onto phase-locked optical carriers, thereby allowing to complement the massive spatial parallelization of digital CMOS circuits by a massive spectral parallelization of DAC interfaces. The approach lends itself to large-scale photonic-electronic integration and is scalable to waveform generation at analogue bandwidths of hundreds of GHz.

As one of the most crucial aspects, this GOSPEL scheme relies on novel stabilization concepts that allow to coherently superimpose optical tributary waveforms that have been generated in independent functional units of a large-scale photonic-electronic system and that are hence subject to phase and frequency uncertainties and to temporal phase drifts. The stabilization concept is based on digital control loops, which compensate for circuit and device-related non-idealities and allow for phase and frequency stabilization of the optical carriers using integrated optical frequency shifters. Another key aspect is the conversion of the broadband photonic waveform to an electrical waveform, which requires an ultra-broadband photodetector featuring analogue bandwidths of hundreds of GHz. To this end, we will exploit so-called plasmonic internal photoemission detectors (PIPED) that we have recently demonstrated for the first time. PIPED are ultra-compact devices that can be monolithically co-integrated on the silicon photonic platform. Within GOSPEL, we will systematically explore variations of device concepts, geometries, and materials to increase the output power of PIPED-based converters.

GOSPEL is designed for an overall project duration of 6 years and subdivided into two phases. In Phase I, which is subject of this funding proposal, we aim at establishing the theoretical base of the concept along with the associated quantitative mathematical models, at designing, implementing and testing the crucial components and subsystems, and at demonstrating the viability of the approach in basic proof-of-concept experiments. Based on this, Phase II will be dedicated to realizing an integrated system that optimally combines a multitude of high-performance electronic/photonic components and digital circuits using both hybrid and monolithic integration approaches.