A phase-modulation interferometer for intense, ultrashort, near-infrared laser pulses

The investigation of coherent phenomena in strong-field processes requires interferometric measurement schemes with high selectivity to disentangle the complex nonlinear response of the system. Interferometers combining acousto-optical phase modulation with lock-in detection feature excellent dynamic range and highly selective detection, thus providing a promising solution. However, acousto-optical modulators (AOMs) cause several issues when operated with intense, ultrashort, near-infrared (NIR) laser pulses. The AOMs introduce temporal and angular dispersion, self-phase modulation, and reduced acousto-optic efficiency at NIR wavelengths. Here, we present an acousto-optical phase modulation interferometer design that solves these issues. The presented solutions pave the way for the investigation of strong-field processes with phase-modulated interferometry and are also useful to improve the performance of phase-modulation interferometers in other applications.