Highly Nondegenerate Two-Photon Absorption in Silicon Wire Waveguides

Abstract

Non-degenerate two-photon absorption (TPA) is investigated in a nanophotonic silicon waveguide in a configuration such that the dispersion of the nonlinear absorption and refraction cannot be neglected. It is shown that a signal wave can strongly be absorbed by cross-TPA by interaction with a low energy pump pulse (1.2 pJ), close to the half-bandgap and experiencing low nonlinear absorption. The experiments are very well reproduced by numerical simulations of two-coupled generalized nonlinear Schrödinger equations (GNLSE), validating the usual approximation made to compute the cross nonlinear coefficients in indirect-gap semiconductors. We show that the nonlinear dynamics can be well described by a single GNLSE despite the wavelength separation between the pump and the signal waves. We also demonstrate that in silicon wire waveguides and contrary to optical fibers, the dispersion of the nonlinear absorption is much larger than the dispersion of the Kerr effect. This could have an impact in the design of all-optical functions based on cross-TPA, as well as on the study of supercontinuum and frequency comb generation in integrated semiconductoron-insulator platforms.

Infrared chemical imaging through nondegenerate two-photon absorption in silicon-based cameras

“…The latter two models agree well with degenerate absorption experiments [39]. For the case of NTA, experiments demonstrate enhancement behavior similar to those seen in direct-bandgap semiconductors' [40,41], with the "allowedallowed" pathways providing the best description [42]. Modest numbers of the acquired and derived nonlinear absorption coefficients of only a few cm/GW have classified Si as a rather inefficient material for NTA.…”

A silicon source of heralded single photons at 2 μm

“…27 In particular, XTPA affects more the idler photon than the signal photon, since the lower energy of the signal photon leads to a reduced probability of the process. 28 TPA, XTPA, and FCA play an important role in increasing the losses in the waveguide for both the pump and the generated photons. As a result, the detection probabilities are no longer quadratic with the input pump power.…”

Infrared chemical imaging through non-degenerate two-photon absorption in silicon-based cameras

“…The latter two models agree well with degenerate absorption experiments 43 . For the case of NTA, experiments demonstrate enhancement behaviour similar to those seen in direct-bandgap semiconductors 44 , 45 , with the “allowed-allowed” pathways providing the best description 46 . Modest numbers of acquired and derived nonlinear absorption coefficients of only a few cm/GW have classified Si as a rather inefficient material for NTA.…”