Second Harmonic Generation in Germanium Quantum Wells for Nonlinear Silicon Photonics
Artikel i vetenskaplig tidskrift, 2021
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 μm. Leveraging on the strong intersubband dipoles, the nonlinear susceptibility χ(2) almost reaches 105 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.
quantum wells
silicon photonics
mid-infrared
nonlinear optics
germanium
Författare
Jacopo Frigerio
Politecnico di Milano
Chiara Ciano
Universita degli studi - Roma Tre
Joel Kuttruff
Universität Konstanz
Andrea Mancini
Ludwig-Maximilians-Universität München (LMU)
Sapienza, Università di Roma
Andrea Ballabio
Politecnico di Milano
Daniel Chrastina
Politecnico di Milano
Virginia Falcone
Politecnico di Milano
Monica De Seta
Universita degli studi - Roma Tre
L. Baldassarre
Sapienza, Università di Roma
Jonas Allerbeck
Université du Luxembourg
Universität Konstanz
Daniele Brida
Université du Luxembourg
Lunjie Zeng
Chalmers, Fysik, Nano- och biofysik
Eva Olsson
Chalmers, Fysik, Nano- och biofysik
Michele Virgilio
Universita di Pisa
M. Ortolani
Sapienza, Università di Roma
ACS Photonics
2330-4022 (eISSN)
Vol. 8 12 3573-3582Ämneskategorier
Atom- och molekylfysik och optik
Annan fysik
Den kondenserade materiens fysik
DOI
10.1021/acsphotonics.1c01162