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 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.

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; Ortolani, Michele. - In: ACS PHOTONICS. - ISSN 2330-4022. - 8:12(2021), pp. 3573-3582. [10.1021/acsphotonics.1c01162]

Second Harmonic Generation in Germanium Quantum Wells for Nonlinear Silicon Photonics

Ciano, Chiara;Mancini, Andrea;Baldassarre, Leonetta;Ortolani, Michele
Ultimo
Writing – Original Draft Preparation
2021

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 μm. Leveraging on the strong intersubband dipoles, the nonlinear susceptibility χ(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.
2021
nonlinear optics, integrated optics, quantum wells, mid infrared
01 Pubblicazione su rivista::01a Articolo in rivista
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; Ortolani, Michele. - In: ACS PHOTONICS. - ISSN 2330-4022. - 8:12(2021), pp. 3573-3582. [10.1021/acsphotonics.1c01162]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1591290
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