Spatiotemporal control of laser intensity using differentiable programming

TL;DR

This paper introduces a differentiable programming approach to optimize laser pulse structures for improved spatiotemporal control in nonlinear optics and plasma physics applications.

Contribution

It combines unidirectional pulse propagation with gradient-based optimization to design novel structured laser pulses with enhanced performance.

Findings

Achieved uniform intensity over extended regions

Created superluminal intensity peaks with constant properties

Optimized plasma formation with 15-fold performance improvement

Abstract

Optical techniques for spatiotemporal control can produce laser pulses with custom amplitude, phase, or polarization structure. In nonlinear optics and plasma physics, the use of structured pulses typically follows a forward design approach, in which the efficacy of a known structure is analyzed for a particular application. Inverse approaches, in contrast, enable the discovery of new structures with the potential for superior performance. Here, an implementation of the unidirectional pulse propagation equation that supports automatic differentiation is combined with gradient-based optimization to design structured pulses with features that are advantageous for a range of nonlinear optical and plasma-based applications: (1) a longitudinally uniform intensity over an extended region, (2) a superluminal intensity peak that travels many Rayleigh ranges with constant duration, spot size, and amplitude, and (3) a laser pulse that ionizes a gas to form a uniform column of plasma. In the final case, optimizing the full spatiotemporal structure improves the performance by a factor of 15 compared to optimizing only spatial or only temporal structure, highlighting the advantage of spatiotemporal control.