Measurement and Model of the Infrared Two-Photon Emission Spectrum of GaAs

Two-photon emission from semiconductors was recently observed, but not fully interpreted. We develop a dressed-state model incorporating intraband scattering-related level broadening, yielding nondivergent emission rates. The spectrum calculations for high carrier concentrations including the time dependence of the screening buildup correspond well to our measured two-photon emission spectrum from GaAs.

Figure 1

Transitions diagrams (a) semiconductor TPE transition—the solid arrows indicate the actual transitions via virtual states, while the dash-dotted arrows indicate the contributions of the CB and VB intermediate states to the calculation. (b) A Feynman diagram of a second-order TPE with the crystal electron state described as an interaction with the static crystal potential, depicted by a straight line, while the photons are represented by wavy lines (c) Dressed-state first-order TPE. The dressed crystal electron state is represented by a zigzag line.

Figure 2

TPE spectrum versus energy normalized by the average carrier energy. Experimental measurements are marked by blue triangles, solid black line is the experimental quadratic fit, while the $1\sigma$ variance is denoted by the grayed area; calculated spectrum by the dressed-state method with constant carrier dephasing time of $<100\mathrm{fsec}$ (dashed red line), and calculated spectrum with the frequency-dependent carrier dephasing (dash-dotted purple line).