High Harmonic Interferometry Based on ZnO Microwire Pair

Abstract High harmonic generation (HHG) provides an experimental method for producing attosecond pulses and probing electron dynamics. Achieving precise dipole phase measurements is critical for tailoring the harmonic emission phase and identifying the HHG mechanism. However, achieving this feature by applying traditional two-beam far-field interferometry to solid materials remains challenging. In this study, we present a novel interferometric approach that utilizes a single laser beam to excite two ZnO microwires (MWs) simultaneously, thereby generating coherent high-harmonic sources that form interference fringes in the far-field region. We leverage the diameter-dependent field-enhancement effect in MWs to measure the intensity-dependent fringe shift, revealing that the intraband current mechanism dominates the below-bandgap harmonic, whereas the interband polarization mechanism dominates the above-bandgap harmonic. This study offers a robust method for measuring the dipole phase of solid-state HHG and inspires intensity-modulated high-harmonic applications in coherent imaging and microdevice design.