Second Harmonic Generation in Germanium Quantum Wells for Nonlinear Silicon Photonics

Frigerio, Jacopo; Ciano, Chiara; Kuttruff, Joel; Mancini, Andrea; Ballabio, Andrea; Chrastina, Daniel; Falcone, Virginia; De Seta, Monica; Baldassarre, Leonetta; Allerbeck, Jonas; Brida, Daniele; Zeng, Lunjie; Olsson, Eva; Virgilio, Michele und Ortolani, Michele (2021): Second Harmonic Generation in Germanium Quantum Wells for Nonlinear Silicon Photonics. In: ACS Photonics, Bd. 8, Nr. 12: S. 3573-3582

Abstract

Second-harmonic generation (SHG) is a direct measure of the strength of second-order nonlinear optical effects, which also include frequency mixing and parametric oscillations. Natural and artificial materials with broken center-of-inversion symmetry in their unit cell display high SHG efficiency, however, the silicon-foundry compatible group IV semiconductors (Si, Ge) are centrosymmetric, thereby preventing full integration of second-order nonlinearity in silicon photonics platforms. Here we demonstrate strong SHG in Ge-rich quantum wells grown on Si wafers. Unlike Si-rich epilayers, Ge-rich epilayers allow for waveguiding on a Si substrate. The symmetry breaking is artificially realized with a pair of asymmetric coupled quantum wells (ACQW), in which three of the quantum-confined states are equidistant in energy, resulting in a double resonance for SHG. Laser spectroscopy experiments demonstrate a giant second-order nonlinearity at mid-infrared pump wavelengths between 9 and 12 mu m. Leveraging on the strong intersubband dipoles, the nonlinear susceptibility chi((2)) almost reaches 10(5) pm/V, 4 orders of magnitude larger than bulk nonlinear materials for which, by the Miller's rule, the range of 10 pm/V is the norm.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Physik
• Themengebiete: 500 Naturwissenschaften und Mathematik > 530 Physik
• ISSN: 2330-4022
• Sprache: Englisch