Cryogenic measurement of the DC Kerr and two-photon absorption coefficients at 2 µm using silicon p-i-n diode...

Efficiency of nonlinear interactions in silicon photonics at 1.55 µm is usually limited by two-photon absorption, which can be alleviated by moving to longer wavelengths (> 2 µm). Here, we use an integrated p-i-n diode-based waveguide electro-optic modulator to extract the nonlinear DC Kerr coefficient and the two-photon absorption (TPA) coefficient by measuring the modulation index and photocurrent at 2 µm wavelengths at cryogenic temperatures. We show that while the DC Kerr coefficient stays relatively constant, the TPA coefficient is reduced by 84% moving from 1.55 µm to 2.07 µm, and by a further 90% from 300 K to 4 K at 2.07 µm, showing the viability of the 2 µm band for implementing integrated quantum photonics in silicon.