Chip-Scale Optical Frequency Combs for Communications and Sensing: A Toolkit for System Integration

Project Information

CombTools

Grant agreement ID: 101136978

DOI

10.3030/101136978

EC signature date 9 November 2023

Start date 1 January 2024

End date 31 December 2026

Funded under

• The European Innovation Council (EIC)

Total cost

€ 2 523 585,00

EU contribution

€ 2 523 585,00

Coordinated by

KARLSRUHER INSTITUT FUER TECHNOLOGIE
Germany

Periodic Reporting for period 1 - CombTools (Chip-Scale Optical Frequency Combs for Communications and Sensing: A Toolkit for System Integration)

Reporting period: 2024-01-01 to 2024-12-31

Summary of the context and overall objectives of the project

Chip-scale Kerr comb generators have emerged as a ground-breaking class of light sources with the potential to revolutionize applications such as hyperscale optical communications, LiDAR, high-resolution spectroscopy, and ultra-broadband signal processing. However, despite their promise, Kerr combs have yet to achieve widespread commercial adoption. The primary barriers to commercialization are the lack of high-performance comb generators as commercially available products and the absence of essential tools for comb-based signal processing.

CombTools aims to overcome these challenges by establishing a robust technology foundation and ecosystem to unlock the full potential of Kerr combs in key application areas. At the technology level, we will develop a copper-free silicon nitride photonic integrated circuit with record-low propagation loss. Building on this innovation, CombTools will provide accessible, low-barrier entry to high-performance comb generators, paving the way for numerous follow-on innovations. Additionally, we will develop dedicated tools for comb-based signal processing, including comb line processors, advanced electro-optic modulator arrays, and comb synchronization control modules. The effectiveness of this toolset will be demonstrated through pioneering experiments targeting established markets such as optical and data communications, industrial 3D metrology, photonic-electronic signal processing, and microwave photonics.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Since the project's launch, the CombTools partners have focused on four key activities. First, we have defined the concepts and specifications for the first generation of comb sources and auxiliary subsystems, tailored to meet the requirements of the application demonstrations. Second, we have fabricated Si₃N₄ chips for soliton microcomb generation, which will be packaged in RP2 and later distributed to partners for system-level demonstrations. In parallel, we have worked on the design, fabrication, and characterization of the auxiliary subsystems required to integrate the combs into complete systems. Third, we have begun preparations for the demonstration of comb-based free-space optical (FSO) transmission at Eindhoven, defining the initial specifications of the testbed and characterization setup. Finally, as part of the project’s dissemination efforts, we have participated in trade shows to explore market opportunities for comb technologies, assess industry demand, and evaluate potential commercialization pathways. This comprises a first commercial offering of known-good comb dies that Deeplight is currently establishing.

In the first reporting period, the collaborative efforts of the partners have led to the following highlight results:

• Data transmission at record-high symbol rates using comb-based optical arbitrary waveform generation and measurement (OAWG/OAWM): KIT has implemented schemes for optical arbitrary waveform generation and measurement (OAWG/OAWM) at bandwidths of hundreds of gigahertz. In a collaborative effort with NBL, these schemes were used for long-haul data transmission at record-high single-channel data rates of up to 2.7 Tbit/s. We further demonstrated transmission of single-channel data rates of 1.6 Tbit/s over transatlantic distances. These results were presented at the European Conference of Optical Communications (ECOC) 2024 and subsequently included in a journal publication that is currently under review at the Journal of Lightwave Technology (JLT).

• Advanced fabrication process: EPFL developed a copper-free photonic Damascene Si₃N₄ fabrication process, enhancing performance and scalability with sub dB/m loss.

• World-class testbed: TUE established a cutting-edge FSO testbed with terabit-class data transmission capabilities, providing a crucial platform for further experimentation and validation.

• First commercial offering of die-level Kerr comb generators: DLT is about to establish a commercial offering of known-good die-level comb generators. This is a first step towards thereby “democratizing” chip-scale frequency comb technology and preparing the ground for a wide range of follow-up innovations.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The ground-breaking OAWG/OAWM-based transmission experiments conducted by NBL and KIT showcased the immense potential of comb-based technology, achieving unprecedented single-channel data rates beyond 2 Tbit/s. These results show the viability of comb-based signal processing techniques as a vehicle to advance communication schemes beyond the current state of the art.

EPFL, a leading academic institution and pioneer in microresonator frequency combs, has successfully designed and fabricated a new generation of high-Q microresonators optimized for soliton generation. These microresonators feature ultra-low optical loss and reduced thermal nonlinearity, significantly enhancing their performance. DLT is harnessing the transformative potential of these advancements to democratize access to soliton microcomb technology, making such devices commercially available for the first time.

Deeplight has been working on establishing optical packaging techniques for Kerr comb generators and established first commercialization channels for die-based comb generators. To the best of our knowledge, this offering represents the first commercial access to known-good Kerr-comb dies and will prepare the ground for a wide range of follow-up innovations. Regarding integrated pump sources, DLT has designed a first generation of external feedback circuits that are currently being fabricated by EPFL. The goal is to establish an all-European supply chain for the active elements.

SiN soliton generation chip