Broadband telecom to mid-infrared supercontinuum generation in a dispersion-engineered silicon germanium waveguide

Abstract

We demonstrate broadband supercontinuum generation (SCG) in a dispersion-engineered silicongermanium waveguide. The 3-cm long waveguide is pumped by femtosecond pulses at 2.4µm and the generated supercontinuum extends from 1.45µm to 2.79µm (at the -30-dB point). The broadening is mainly driven by the generation of a dispersive wave in the 1.5-1.8µm region and soliton fission. The SCG was modelled numerically and excellent agreement with the experimental results was obtained. © Silicon (Si) photonics has witnessed rapid maturity in recent years, mainly due to its potential for high-yield, low-cost CMOS-compatible fabrication of components. At the same time, the high nonlinear refractive index of silicon (n 2 = 4.5x10 −18 m 2 /W), especially when combined with small-dimension, high refractive-index-contrast waveguide geometries that lead to tight mode confinement, makes Si photonic technologies particularly attractive for nonlinear applications. Si-based devices have already been utilized to demonstrate numerous all-optical signal processing applications. Indeed, nonlinear effects such as four-wave mixing (FWM) [1], self-phase modulation (SPM) [2] and Raman amplification [3] have been demonstrated in silicon-on-insulator (SOI) waveguides and nanowires designed for operation in the near-infrared (IR).Silicon is also an excellent candidate for mid-IR applications, due to its transparency up to 8µm and to the reduced two-photon and free-carrier absorptions at wavelengths beyond 2.2µm. Leveraging on these attributes, moderate to high brightness wide-bandwidth laser sources have been demonstrated based on supercontinuum generation (SCG) in this wavelength region, using waveguides fabricated on either crystalline silicon [4,5], amorphous silicon [6] or silicon nitride [7]. Furthermore, the development of on-chip sources providing short pulses has driven research towards integrating both the pump source and nonlinear element on the same chip [8].We have recently reported the first demonstrations of alloptical signal processing using silicon germanium waveguides both in the near-[9] and mid-IR [10]. These demonstrations, along with a detailed study on the optical properties of SiGe waveguides [11], have highlighted that the addition of germanium to silicon can enhance the nonlinear response in comparison to pure silicon, as well as act as an additional valuable design parameter that can impact a host of optical properties (such as linear loss, two-photon absorption (TPA) and dispersion) of the nonlinear waveguide.In this Letter, we have extended the work presented in [12] where we reported the generation of a broadband supercontinuum (SC) in a dispersion-engineered SiGe waveguide. The waveguide was pumped using femtosecond pump pulses at 2.4µm and the 30-dB bandwidth of the SC extended more than 1330 nm spanning both the mid-IR and the entire telecommunication wavelength window, while maintaining high spectral uniformity. A numerical model was also developed to study the SCG, providing excellent agreement with the exper...

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Polarization Insensitive Wavelength Conversion in a Low-Birefringence SiGe Waveguide

“…The results reported here further demonstrate the emergence of SiGe devices as a competitive all-optical signal processing technology. The inclusion of Ge in the waveguides facilitates flexible dispersion engineering and enhances the effective nonlinear coefficient, making SiGe technology a versatile choice for a wide range of nonlinear applications [17][18][19].…”

Mid-infrared nonlinear optical response of Si-Ge waveguides with ultra-short optical pulses

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