Efficient Second-Harmonic Generation in Si-GaP Asymmetric Coupled-Quantum-Well Waveguides

We present a theoretical investigation of efficient second harmonic generation in the cubic lattice-matched N-doped Si/GsP multiple quantum well system integrated in a strip waveguide in the silicon-on-insulator platform. A “giant” second-order nonlinear optical susceptibility is obtained in an asymmetric coupled quantum well (ACQW) stack by engineering the 1-2 and 1-3 inter-subband spacings for resonance at both a ∼4 μm pump wavelength and a ∼2μm harmonic wavelength. Generation has been simulated as a function of the quantum well physical parameters, the infrared absorption losses, and the detuning from the double resonance condition. For TM pumps at 3.75 μm and 4.24 μm, a
${\boldsymbol{\chi }}_{{\bm{zzz}}}^{(2)}$
value ranging from 7.73 × 10
³
pm/V to 1.13 × 10
⁴
pm/V has been calculated and a maximum conversion efficiency ranging between 1.23%/W and 1.68%/W has been obtained, where the waveguide coherence length was 5.57 μm and 6.16 μm.