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
${({\mathbf{GaP}})_4}/{({\mathbf{S}{\mathbf{i}_2}})_2}$
.