Harmonic Generation in GaP/Si and GaP/AlP Superlattice-Based Waveguides

We present a theoretical investigation, based on the tight-binding Hamiltonian, of efficient second harmonic generation (SHG) in the lattice-matched N-doped ${({\mathbf{GaP}})_{\boldsymbol{N}}}/{({\mathbf{S}{\mathbf{i}_2}})_{\boldsymbol{M}}}$ short-period superlattice integrated in a strip waveguide in the silicon-on-insulator platform. The ${\boldsymbol{\chi }}_{{\boldsymbol{zzz}}}^{(2)}$ spectrum has been simulated as a function of the number of the monolayers for the “non-relaxed” heterointerfaces. For TM pumps at 5.05 μm a ${\boldsymbol{\chi }}_{{\boldsymbol{zzz}}}^{(2)}$ value of 1.25×10 ⁴ pm/V has been calculated for the ${({\mathbf{GaP}})_1}/{({\mathbf{S}{\mathbf{i}_2}})_2}$ superlattice giving a maximum conversion efficiency around 1.14%/W, where the waveguide coherence length was 3.37 μm and the waveguide width was 2 μm. Moreover the ${({\mathbf{GaP}})_3}/{({\mathbf{AlP}})_3}$ superlattice is proposed for SHG with surface incidence, operating in the mid infrared with ${\boldsymbol{\chi }}_{{\boldsymbol{zzz}}}^{(2)}$ value of 1.8×10 ⁴ pm/V. Finally, the ${\boldsymbol{\chi }}_{{\boldsymbol{zzz}}}^{(2)}$ spectrum for difference frequency generation is reported for ${({\mathbf{GaP}})_5}/{({\mathbf{S}{\mathbf{i}_2}})_1}$ and ${({\mathbf{GaP}})_4}/{({\mathbf{S}{\mathbf{i}_2}})_2}$ .