Enhancement of Two-photon Absorption in Quantum Wells for Extremely Nondegenerate Photon Pairs

TL;DR

This paper provides a theoretical analysis demonstrating that quantum wells significantly enhance nondegenerate two-photon absorption compared to bulk semiconductors, with potential applications in nonlinear optics.

Contribution

The paper introduces a perturbation-theory based model for nondegenerate 2PA in quantum wells, including analytical expressions for various frequency and polarization configurations.

Findings

QWs increase nondegenerate 2PA by an order of magnitude over bulk semiconductors.

Using TM polarization in QWs further enhances 2PA.

Explicit calculations for GaAs QWs support the theoretical predictions.

Abstract

We recently demonstrated orders of magnitude enhancement of two-photon absorption (2PA) in direct gap semiconductors due to intermediate state resonance enhancement for photons of very different energies. It can be expected that further enhancement of nondegenerate 2PA will be observed in quantum wells (QWs) since the intraband matrix elements do not vanish near the band center as they do in the bulk, and the density of states in QWs is larger near the band edge. Here we present a perturbation-theory based theoretical description of nondegenerate 2PA in semiconductor QWs, where both frequency and polarization of two incident waves can vary independently. Analytical expressions for all possible permutations of frequencies and polarizations have been obtained, and the results are compared with degenerate 2PA in quantum wells along with degenerate and nondegenerate 2PA in bulk semiconductors. We show that using QWs in place of bulk semiconductors with both beams in the TM-polarized mode leads to an additional order of magnitude increase in the nondegenerate 2PA. Explicit calculations for GaAs QWs are presented.