On the Inhibition of Linear Absorption in Opaque Materials Using Phase-Locked Harmonic Generation

TL;DR

This paper demonstrates that phase-locking can inhibit linear absorption in strongly absorbing materials like GaAs, enabling efficient harmonic generation at frequencies above the absorption edge.

Contribution

It introduces a novel phase-locking mechanism that allows harmonic generation to occur without absorption in opaque materials, both theoretically and experimentally.

Findings

Harmonic pulses propagate without absorption in GaAs.

Phase-locking traps harmonics with the pump pulse.

Efficient harmonic generation above absorption edge.

Abstract

We theoretically predict and experimentally demonstrate inhibition of linear absorption for phase and group velocity mismatched second and third harmonic generation in strongly absorbing materials, GaAs in particular, at frequencies above the absorption edge. A 100-fs pump pulse tuned to 1300nm generates 650nm and 435nm second and third harmonic pulses that propagate across a 450 micron-thick GaAs substrate without being absorbed. We attribute this to a phase-locking mechanism that causes the pump to trap the harmonics and to impress them with its dispersive properties.