Coherent surface plasmon polariton amplification via free-electron pumping

Area of Science:

• * Physics
• * Optics
• * Materials Science

Background:

• * Surface plasmonics offers unique light confinement for advanced photonic devices.
• * Energy transfer between light and matter is crucial for optical surface-wave studies.
• * Coherent stimulated emission from free electrons is vital for free-electron light sources but remains underexplored.

Purpose of the Study:

• * To demonstrate and investigate the coherent amplification of terahertz surface plasmon polaritons (SPPs) via free-electron-stimulated emission.
• * To elucidate the dynamics and amplification process of terahertz SPPs mediated by free electrons.
• * To explore the potential for developing novel terahertz light sources and matter manipulation tools.

Main Methods:

• * Employed a femtosecond optical pulse to generate an in-phase free-electron pulse synchronized with an initial terahertz surface wave.
• * Utilized an optical pump-probe method to resolve the electromagnetic field profile evolution and underlying amplification dynamics.
• * Conducted theoretical analysis to predict super-radiant surface-wave growth with phase-matched electron bunches.

Main Results:

• * Achieved coherent amplification of terahertz surface plasmon polaritons through free-electron-stimulated emission.
• * Observed a twofold redshift in radiation frequency over a 1 mm interaction length, revealing amplification dynamics.
• * Demonstrated the intensification of the terahertz surface wave through the interaction of synchronized electron and surface wave pulses.

Conclusions:

• * The study presents a novel method for coherent amplification of terahertz SPPs using free electrons.
• * The findings pave the way for compact, stimulated terahertz surface-wave light sources.
• * This approach holds promise for advanced applications in matter manipulation, particularly in the terahertz frequency range.