Reflection-geometry propagation effects in the higher-order harmonic radiation from solid-state materials

While the propagation effects are known to exhibit strong influence on the solid-state, higher-order harmonic generation in the transmission geometry, it has been assumed that they are negligible in the reflection geometry. This work shows that because the "reflected" high-frequency radiation originates from a material layer several hundred nanometers thick, the propagation effects, while weak, are not completely negligible. Unlike the transmission geometry which requires significant additional numerical effort, the reflection geometry admits a computationally inexpensive way to relate the simulated and measured high-harmonic spectra. (c) 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement