Two-Photon Photovoltaic Effect in Silicon

Optical amplification, wavelength conversion, and a myriad of other functions that were once considered to be beyond silicon's reach have been made possible by the material's nonlinear optical properties. The common feature of such devices is the high optical intensity that is required to induce the nonlinear optical interactions. Concurrent with the useful nonlinearities (Raman and Kerr) are two-photon absorption and free carrier scattering, which are two related and harmful phenomena that render silicon lossy at high intensities. This paper explores the use of the two-photon photovoltaic effect as a means to counter these phenomena in an energy-efficient manner. The effect reduces losses due to free carrier scattering and serendipitously scavenges the optical energy lost to two-photon absorption. Analytical and numerical modeling of the two-photon photovoltaic effect in silicon devices is presented. The model is validated through comparison with experimental results and is used to establish the limits of this approach for creating energy-efficient silicon photonic devices.