Abstract
We experimentally demonstrate supercontinuum (SC) generation in a germanium-on-silicon waveguide. This waveguide exhibits propagation loss between 1.2 dB/cm and 1.35 dB/cm in the 3.6 µm–4.5 µm spectral region for both transverse electric (TE) and transverse magnetic (TM) polarizations. By pumping the waveguide with ∼200 fs pulses at 4.6 µm wavelength, we generate a mid-infrared (IR) SC spanning nearly an octave from 3.39 µm to 6.02 µm at the −40 dB level. Through numerical analysis of the evolution of the SC, we attribute the current limit to further extension into the mid-IR mainly to free-carrier absorption.
Highlights
Group IV photonics has witnessed remarkable growth over the past two decades and is emerging as a mature technology
The spectral range over which group IV photonics could operate was initially limited to the near infrared (IR), the last decade has seen this range extended to the mid- and even long-infrared regions
Mid-infrared is attracting particular attention because of the strong absorption fingerprint of molecules in this spectral region, which includes two main atmospheric transparency windows between 3–5 and 8–12 μm.2. This makes it possible to consider spectroscopy, chemical and biological sensing, environmental monitoring, and free-space optical communications all using integrated photonic chips based on group IV materials
Summary
Group IV photonics has witnessed remarkable growth over the past two decades and is emerging as a mature technology. Mid-infrared is attracting particular attention because of the strong absorption fingerprint of molecules in this spectral region, which includes two main atmospheric transparency windows between 3–5 and 8–12 μm.. Mid-infrared is attracting particular attention because of the strong absorption fingerprint of molecules in this spectral region, which includes two main atmospheric transparency windows between 3–5 and 8–12 μm.2 This makes it possible to consider spectroscopy, chemical and biological sensing, environmental monitoring, and free-space optical communications all using integrated photonic chips based on group IV materials.. Scitation.org/journal/app several germanium-based active and passive mid-infrared devices have been realized, such as (de)multiplexers, all-optical modulators, micro-resonators, Mach–Zender interferometers, Fourier-transform spectrometers, micro-lasers, and polarization rotators.22 Despite this intense research activity, the demonstration of a broadband source afforded by the strong nonlinear response of a pure germanium waveguide is still lacking. Through our simulations and data analysis, we mainly attribute the current long wavelength extension limit to absorption from free carriers generated by three-photon absorption, which significantly increases beyond 6 μm wavelength in Ge
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