From SHG to mid-infrared SPDC generation in strained silicon waveguides

The centrosymmetric crystalline structure of Silicon inhibits second order nonlinear optical processes in this material. We report here that, by breaking the silicon symmetry with a stressing silicon nitride over-layer, Second Harmonic Generation (SHG) is obtained in suitably designed waveguides where multi-modal phase-matching is achieved. The modeling of the generated signal provides an effective strain-induced second order nonlinear coefficient of χ(2) = (0.30 ± 0.02) pm/V. Our work opens also interesting perspectives on the reverse process, the Spontaneous Parametric Down Conversion (SPDC), through which it is possible to generate mid-infrared entangled photon pairs.

[1]  Mher Ghulinyan,et al.  Homodyne Detection of Free Carrier Induced Electro-Optic Modulation in Strained Silicon Resonators , 2016, Journal of Lightwave Technology.

[2]  L. Vivien,et al.  Wavelength dependence of Pockels effect in strained silicon waveguides. , 2014, Optics express.

[3]  Delphine Marris-Morini,et al.  Bond orbital description of the strain-induced second-order optical susceptibility in silicon , 2015, 1511.03041.

[4]  Mher Ghulinyan,et al.  Second‐Order Optical Nonlinearity in Silicon Waveguides: Inhomogeneous Stress and Interfaces , 2015 .

[5]  J. Witzens,et al.  High-frequency electro-optic measurement of strained silicon racetrack resonators. , 2015, Optics letters.

[6]  Heinrich Kurz,et al.  Investigation of local strain distribution and linear electro-optic effect in strained silicon waveguides. , 2013, Optics express.

[7]  J. Witzens,et al.  On the measurement of the Pockels effect in strained silicon. , 2015, Optics letters.

[8]  Jeppe Seidelin Dam,et al.  Room-temperature mid-infrared single-photon spectral imaging , 2012, Nature Photonics.

[9]  G. Fontana,et al.  Mid-infrared coincidence measurements on twin photons at room temperature , 2017, Nature Communications.

[10]  H. Driel,et al.  Two-photon absorption and Kerr coefficients of silicon for 850–2200nm , 2007 .

[11]  Michael Nagel,et al.  Pockels effect based fully integrated, strained silicon electro-optic modulator. , 2011, Optics express.

[12]  S Wabnitz,et al.  Second-harmonic generation in silicon waveguides strained by silicon nitride. , 2012, Nature materials.

[13]  Yeshaiahu Fainman,et al.  Observation of second-harmonic generation in silicon nitride waveguides through bulk nonlinearities. , 2016, Optics express.

[14]  Yeshaiahu Fainman,et al.  Tensor of the second-order nonlinear susceptibility in asymmetrically strained silicon waveguides: analysis and experimental validation. , 2014, Optics letters.

[15]  O. Hansen,et al.  Strained silicon as a new electro-optic material , 2006, Nature.

[16]  Claudio Castellan,et al.  Nonlinear silicon photonics , 2015 .