Low-Voltage Electrically-Induced Second Harmonic Generation in a Silicon Waveguide Based on Modal Phase Matching

Design and analysis of a silicon waveguide with embedded pin diode are proposed here for the realization of second harmonic generation (SHG). The reverse-biased pin structure is employed to apply a DC field across an intrinsic silicon region which gives rise to electric-field induced (EFI) second-order nonlinearity χ
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EFI in silicon. The resulted χ
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EFI is then used to generate a second harmonic (SH) frequency of an input 2.29-μm signal in which second-order mode at 1.145 μm is used to satisfy modal phase matching with fundamental mode at 2.29 μm through suitably designing the silicon waveguide. It is shown that by engineering the geometry of pin diode, not only a high modal overlap integral is yielded by eliminating the counteractive parts of second-order mode at SH wavelength but also the required external voltage to induce the possible maximum achievable χ
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EFI is significantly reduced compared to the previous SHG structure with the EFI nonlinearity. The simulation results in P2ω /Pω = 6.5% for a pump power of 25 mW and only 7.6 V external voltage which can be improved up to 27% by increasing the input power to 260 mW.