Generation, detection, and processing of electrical and electromagnetic waveforms is one of the most important technical foundations of modern society. In particularly digital signal processing (DSP) has revolutionized many areas of science and engineering, with widespread applications in communications, radar and navigation, industrial metrology and sensing, chemical analysis, or medical diagnostics. Over the previous decades, the processing power of digital computing systems increased by orders of magnitude, mainly driven by the tremendous evolution and the outstanding scalability of complementary metal-oxide-semiconductor (CMOS) electronics. This has opened a door towards real-time processing of data streams of hundreds of gigabits per second, exploiting massively parallel computation on tens of billions of transistors at comparatively low internal clock speed. In contrast to this, the analogue bandwidth of electronic circuits is much more difficult to scale due to limited switching speed of semiconductor devices, strongly increased transmission line losses at high frequencies, and the considerable complexity associated with high-speed circuit packaging and assembly.
The goal of TeraSHAPE was to overcome these limitations by establishing the methodological and technological foundations of novel signal processing concepts in the frequency range between 100 GHz and 1 THz. By combining massively parallel processing in digital electronic circuits with synthesis and analysis of broadband waveforms in the optical domain, signal processing bandwidths of hundreds of gigahertz come into reach. This approach could capitalize on great progress in the fields of photonic integrated circuits (PIC) and optical frequency combs, which act as precise references for broadband signal generation and detection. Specifically, we exploited powerful PICs for spectrally sliced processing of phase-locked optical carriers that are derived from chip-scale frequency comb sources. To convert waveforms between optical and THz frequencies, TeraSHAPE explored novel concepts for ultra-fast electro-optic modulators and photodetectors with bandwidths of hundreds of gigahertz. Advances on the device level were complemented by scalable assembly concepts for high-performance systems, where TeraSHAPE focussed on three-dimensional additive fabrication techniques both for hybrid photonic integration and for THz system assembly. The viability and the application potential of the TeraSHAPE concepts were explored and demonstrated in dedicated experiments that target selected applications of high relevance, comprising, e.g. high-speed wireless communications in future sixth generation (6G) wireless networks or THz signal processing for scientific applications. The project has built the technology base of several start-up companies that transfer the scientific results to industrial use cases.
