Visible Octave Frequency Combs in Silicon Nitride Nanophotonic Waveguides Driven by Ti:Sapphire Lasers

Alabbadi A, Allan E, Ostapenko H, Castro-Marín P, Reid DT, Del'Haye P (2026)

Publication Type: Journal article

Publication year: 2026

Journal

Laser & Photonics Reviews Wiley-VCH Verlag

DOI: 10.1002/lpor.71640

Abstract

Nonlinear nanophotonic waveguides have opened a route to compact frequency combs for precision metrology, spectroscopy and astronomy, yet broadband comb access to the visible remains challenging on CMOS-compatible platforms. Silicon nitride is widely accessible and low-loss into the visible, but most demonstrations rely on telecom pumping and thick stress-managed films, where the large spectral gap to the visible dispersive wave raises the soliton order and power required for efficient conversion. Here we show that pumping closer to the visible provides a complementary route. Starting from crack-free, 400-nm-thick Si3N4 films, we implement dispersion engineering with air-clad nanophotonic waveguides whose enhanced geometric dispersion opens an anomalous-dispersion window across the Ti:sapphire tuning range. Femtosecond Ti:sapphire pulses then drive octave-spanning combs from the visible to the infrared, with the visible edge and attainable bandwidth controlled by the waveguide width at pulse energies of only tens of picojoules. The air-clad geometry produces strong polarization-dependent dispersion, enabling switching between all-normal and soliton-dominated broadening in the same device, and supporting octave-spanning combs at 1 GHz repetition rates directly driven by a compact diode-pumped Ti:sapphire oscillator. These results position air-clad Si3N4 nanophotonic waveguides as an interface between emerging short-wavelength integrated gain platforms and fully integrated visible frequency-comb engines.

Authors with CRIS profile

Pascal Del'Haye

Involved external institutions

Heriot-Watt University GB United Kingdom (GB) Max-Planck-Institut für die Physik des Lichts (MPL) / Max Planck Institute for the Science of Light DE Germany (DE)

How to cite

APA:

Alabbadi, A., Allan, E., Ostapenko, H., Castro-Marín, P., Reid, D.T., & Del'Haye, P. (2026). Visible Octave Frequency Combs in Silicon Nitride Nanophotonic Waveguides Driven by Ti:Sapphire Lasers. Laser & Photonics Reviews. https://doi.org/10.1002/lpor.71640

MLA:

Alabbadi, Abdullah, et al. "Visible Octave Frequency Combs in Silicon Nitride Nanophotonic Waveguides Driven by Ti:Sapphire Lasers." Laser & Photonics Reviews (2026).

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