This paper demonstrates the generation of visible octave-spanning frequency combs using air-clad silicon nitride (Si₃N₄) nanophotonic waveguides, driven by a Ti:sapphire laser. The study focuses on overcoming the challenges associated with generating broadband visible combs on CMOS-compatible platforms. By engineering dispersion in the waveguide and utilizing femtosecond pulses from the Ti:sapphire laser, the authors achieve octave-spanning combs from the visible to near-infrared region with pulse energies as low as tens of picojoules.
The paper explores the use of air-clad Si₃N₄ waveguides, which provide enhanced geometric dispersion, enabling efficient supercontinuum generation. The waveguide's dispersion is tuned by the width of the waveguide, allowing the control of the visible and near-infrared edges of the comb. A key advantage of the air-clad geometry is its strong polarization-dependent dispersion, allowing the same device to operate in both soliton-dominated and all-normal dispersion regimes by simply rotating the input polarization.
The results demonstrate the capability of generating octave-spanning combs at 1 GHz repetition rates directly driven by a compact diode-pumped Ti:sapphire oscillator. These findings position air-clad Si₃N₄ waveguides as an efficient interface for emerging integrated gain platforms and fully integrated visible frequency-comb engines, with potential applications in metrology, spectroscopy, and astronomical observations. The paper concludes with the prospects of further integration of Ti:sapphire gain media with Si₃N₄ nonlinear waveguides for fully integrated, high-performance visible photonic engines.
OMeda (Shanghai Omedasemi Co.,Ltd) was founded in 2021 by 3 doctors with more than 10 years of experience in nanpfabrication. It currently has 15 employees and has rich experience in nanofabrication (coating, lithography, etching, two-photon printing, bonding) and other processes. We support nanofabrication of 4/6/8-inch wafers.
