Quantum echo-enabled high harmonic generation using ultrafast electrons

TL;DR

This paper introduces a quantum echo-enabled high-harmonic generation scheme that manipulates electron wavepackets to produce tunable, coherent high-harmonic radiation at ultrashort wavelengths, advancing compact light sources.

Contribution

It proposes a novel quantum echo technique inspired by EEHG for free-electron lasers, enabling selective enhancement of specific high harmonics through quantum interference.

Findings

Achieved generation of the 60th harmonic at 13.3nm from 800nm seed

Demonstrated suppression of unwanted radiations via quantum interference

Analyzed the spectral characteristics and optimization of harmonic orders

Abstract

Controlling and generating ultrafast free-electron wavepackets via laser is pivotal for photon-induced near-field electron microscopes (PINEM) and also for developing compact, coherent free-electron radiation sources. Here, we present a quantum echo-enabled high-harmonic generation (QEEHG) scheme that manipulates the quantum phase of electron wavepackets to produce tunable, coherent high-harmonic radiation at ultrashort wavelengths. This framework, inspired by the EEHG concept for free-electron lasers by Stupikov et al. (2009), leverages multiphoton PINEM scattering followed by dispersive chirp sections to induce quantum interference among photon sidebands. Such interference selectively enhances a targeted harmonic order - for instance, the 60th harmonic at 13.3nm from an 800nm seeding - while suppressing unwanted radiations. The optimization of harmonic orders and its non-classical spectral characteristics are analyzed. This quantum echo technique establishes a promising paradigm for compact coherent sources and provides new perspectives for quantum wavefunction shaping in ultrafast electron microscopy and diffraction.