Mid-infrared spectroscopy is a universal way to identify chemical and biological substances. Indeed, when interacting with a light beam, most molecules are responsible for absorption at specific wavelengths in the mid-IR spectrum, allowing to detect and quantify small traces of substances. On-chip broadband light sources in the midinfrared are thus of significant interest for compact sensing devices. In that regard, supercontinuum generation offers a mean to efficiently perform coherent light conversion over an ultrawide spectral range, in a single and compact device. This work reports the experimental demonstration of on- chip two-octave supercontinuum generation in the mid-infrared wavelength, ranging from 3 to 13 μm and covering almost the full transparency window of germanium. Such an ultrawide spectrum is achieved thanks to the unique features of Ge-rich graded SiGe waveguides, which allow second-order dispersion tailoring and low propagation losses over a wide wavelength range. This results also rely on the use of a Ge-rich approach which benefits from a large Kerr coefficient and tight confinement, thus, enhancing the nonlinear processes.
In summary, these results pave the way toward an efficient ultrawide mid-IR light source implementation by using a single and compact on-chip device.
M. Montesinos-Ballester1, C. Lafforgue1, J. Frigerio2, A. Ballabio2, V. Vakarin1, Q. Liu1, J. M. Ramirez1, X. Le Roux1, D. Bouville1, A. Barzaghi2, C. Alonso-Ramos1, L. Vivien1, G. Isella2, D. Marris-Morini1
ACS Photonics2020, 7, 3423−3429, 2020
DOI : doi/10.1021/acsphotonics.0c01232
1 Center of Nanosciences and Nanotechnologies - C2N (CNRS, Paris-Saclay University)
2 L-NESS, Dipartimento di Fisica, Politecnico di Milano, Polo di Como, Via Anzani 42, 22100 Como, Italy
Miguel Montesinos-Ballester : Center of Nanosciences and Nanotechnologies - C2N (CNRS, Paris-Saclay University)
Delphine Marris - Morini : Center of Nanosciences and Nanotechnologies - C2N (CNRS, Paris-Saclay University)
figure : Output power spectral density experimentally measured in a 5.5 mm-long waveguide for different input average power values at 7.5 µm fixed wavelength. For the sake of clarity, each trace has been shifted by 30 dB.