Canonical Clocks and Hidden Geometric Freedom in Self-Imaging

TL;DR

This paper reveals that self-imaging effects in wave evolution are fundamentally linked to a canonical coordinate called metaplectic time, which can be engineered to control axial dynamics, enabling novel self-imaging patterns.

Contribution

The authors reframe self-imaging within a symplectic framework, showing that the canonical evolution coordinate allows arbitrary engineering of recurrence spacings and trajectories.

Findings

Demonstrated acceleration and deceleration of recurrence spacings.

Created self-imaging patterns with polynomial, exponential, and sinusoidal axial trajectories.

Established metaplectic time as the fundamental invariant of self-imaging.

Abstract

Self-imaging represents a core hallmark of paraxial (quadratic)-wave evolution; yet, across its many realizations and generalizations over the past two centuries, the uniformity of recurrence planes along the propagation axis has been considered fundamental. However, by reframing the general phenomenon of self-imaging within its natural symplectic framework, we show that all self-imaging effects are necessarily tied to uniformly periodic recurrences in the canonical evolution coordinate -- metaplectic time -- and that the correspondence of that coordinate to the physical propagation axis represents an unexplored degree of freedom, which can be engineered arbitrarily by the initial transverse phase structure. Using a single programmable spatial light modulator, we demonstrate the construction of Talbot carpets characterized by recurrence spacings that accelerate and decelerate along the propagation axis, as well as those that follow polynomial, exponential, and sinusoidal axial trajectories, all of which preserve exact reconstruction in the canonical metaplectic time. These results establish metaplectic time as the fundamental invariant of self-imaging and reveal a regime of controllable axial dynamics previously thought to be fixed.