# Harnessing Electro-Optic Modulation and On-Chip Temporal Interleaving Towards Versatile Frequency Comb Generation

Manal Arbati, Alexis Bougaud, Bruno P Chaves, Thomas Bunel, S. Février, B. Little, S. Chu, D. Moss, R. Morandotti, A. Mussot, et al.

► To cite this version:

Manal Arbati, Alexis Bougaud, Bruno P Chaves, Thomas Bunel, S. Février, et al. Harnessing Electro-Optic Modulation and On-Chip Temporal Interleaving Towards Versatile Frequency Comb Generation. 2025 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), Jun 2025, Munich, Germany. 10.1109/CLEO/Europe-EQEC65582.2025.11109983. [hal-05240466]

HAL Id: hal-05240466

https://hal.science/hal-05240466v1

Submitted on 29 Sep 2025

**HAL** is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire **HAL**, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# Harnessing Electro-Optic Modulation and On-Chip Temporal Interleaving Towards Versatile Frequency Comb Generation

M. Arbati¹, A. Bougaud¹, B. P. Chaves¹, T. Bunel², S. Février¹, B. Little³, S. T. Chu⁴, D. J. Moss⁵,
R. Morandotti⁶, A. Mussot², B. Wetzel¹

1. XLIM Research Institute, CNRS UMR 7252, Université de Limoges, Limoges 87060, France

2. Université de Lille, CNRS, UMR 8523—PhLAM—Physique des Lasers Atomes et Molécules, F-59000, Lille, France

3. QXP Technologies Inc., Xi’an, China

4. Department of Physics, City University of Hong Kong, Hong Kong, China

5. Optical Sciences Centre, Swinburne University of Technology and the Australian Research Council (ARC) Centre of Excellence in Optical Microcombs for Breakthrough Science, COMBS (CE230100006), Hawthorn, Victoria, Australia

6. INRS-EMT, 1650 Boulevard Lionel-Boulet, Varennes, J3X 1S2, Québec, Canada

Frequency combs (FCs) have advanced a wide range of scientific fields including spectroscopy, optical communication, and metrology [1]. First developed using mode-locked lasers [2], optical FCs usually rely on stabilization schemes and feedback loops to control the free spectral range (FSR) and the spectral envelope of the comb. Despite the effectiveness of these systems, they often require complex setups and lack tunability. As an alternative, electro-optical modulation (EOM), allows precise control of the FSR and easy implementation with other nonlinear optical systems for versatile applications. However, the limited bandwidth of standard EOMs (~50 GHz) restricts the achievable optical spectral profile and bandwidth [3]. To unlock advanced FC tunability, one usually necessitates a cascade of EOMs at the expense of higher losses and complexity, ultimately reaching limited tunability in the output spectral shape. Here, we propose a new approach for versatile frequency comb generation, using a hybrid architecture leveraging EOM picosecond pulse generation paired with adjustable temporal interleaving provided by a photonic integrated circuit (PIC) [4,5]. The setup, illustrated in Fig. 1(a), is based on an electrical pulse generator (EPG) driving a 20 GHz intensity EOM. Modulating a 1560 nm continuous laser, the system is first used to generate a ~20 ps pulse train with an adjustable repetition rate in the 0.1-10 GHz range. The pulse train is then sent into the PIC encompassing a set of Mach Zehnder interferometers and optical delay lines that allow for adjustable pulse interleaving within the 1-255 ps range (i.e. equivalent to a static modulation up to the THz). Such a coherent superposition of interleaved pulses (yielding different interference patterns as a function of the chosen PIC configuration) is amplified via an Erbium doped fiber amplifier (EDFA) before propagation into a 500 m highly non-linear fiber (HNLF) operating in an anomalous dispersion regime. Figure 1(b-e) shows experimental results at the fiber output, illustrating examples of reconfigurable FCs where the RF and optical spectra are tailored to selectively suppress or enhance specific frequency components. For instance, to demonstrate the versatility of our approach while driving the EPG at 2 GHz, we experimentally show > 44 dB extinction of the 16 GHz harmonic in the RF spectrum while covering ~ 80 nm in the optical spectrum (Fig. 1(b) - blue lines), or conversely, > 15 dB isolation of the 8 GHz harmonic (Fig. 1(c) - red lines). We further discuss the impact of coherent pulse superposition in FC broadening through cascaded frequency conversion, and the potential of machine learning techniques for on-demand FC tailoring within our hybrid architecture.

<figure><img src="image_2.png" /><figcaption>**Fig. 1** Experimental setup for versatile FC generation. (b-c) RF spectra with selective RF comb shaping, (b) at 16 GHz with > 44 dB extinction, (c) at 8 GHz with > 15 dB selective isolation. (d-e) Corresponding (color-coded) optical spectra of tailored FCs shown in (b-c). (e) Zoom in the central optical FC region with respective spectra shifted for clarity.</figcaption></figure>

## References

[1] T. Fortier and E. Baumann, "20 years of developments in optical frequency comb technology and applications," Commun. Phys. **2**, 153 (2019)

[2] T. W. Hänsch, "Nobel Lecture: Passion for precision," Rev. Mod. Phys. **78**, 1297-1309 (2006).

[3] A. Parriaux, K. Hammani, and G. Millot, "Electro-optic frequency combs," Adv. Opt. Photon. **12**, 223 (2020).

[4] B. Wetzel, et al., "Customizing supercontinuum generation via on-chip adaptive temporal pulse-splitting," Nat. Commun. **9**, 4884 (2018).

[5] B. Fischer, et al., "Autonomous on-chip interferometry for reconfigurable optical waveform generation," Optica **8**, 1268(2021).