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arXiv · 2103.12620

Second harmonic generation in germanium quantum wells for nonlinear silicon photonics

Jacopo Frigerio·Chiara Ciano·Joel Kuttruff·Andrea Mancini·Andrea Ballabio·Daniel Chrastina·Virginia Falcone·Monica De Seta·Leonetta Baldassarre·Jonas Allerbeck·Daniele Brida·Lunjie Zeng·Eva Olsson·Michele Virgilio·Michele Ortolani
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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. 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 microns. Leveraging on the strong intersubband dipoles, the nonlinear susceptibility almost reaches 10^5 pm/V

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Jacopo Frigerio, Chiara Ciano, Joel Kuttruff, Andrea Mancini, Andrea Ballabio, Daniel Chrastina, Virginia Falcone, Monica De Seta, Leonetta Baldassarre, Jonas Allerbeck, Daniele Brida, Lunjie Zeng, Eva Olsson, Michele Virgilio, Michele Ortolani. 2021-03-23. Second harmonic generation in germanium quantum wells for nonlinear silicon photonics. https://arxiv.org/abs/2103.12620

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