High-order-harmonic generation and superradiance in a seeded free-electron laser

Area of Science:

• Physics
• Laser Science
• Quantum Optics

Background:

• Superradiance is a quantum optical phenomenon where emitters release photons coherently.
• Free-electron lasers (FELs) are powerful light sources that can operate in the superradiant regime.
• Harmonic generation is crucial for extending the spectral range of light sources.

Purpose of the Study:

• To investigate higher order harmonic generation in a superradiant free-electron laser.
• To explore the induction of superradiance by seeding with a Ti:sapphire laser's second harmonic.
• To analyze the energy and spectral characteristics of generated harmonics.

Main Methods:

• Utilized a single-pass free-electron laser amplifier.
• Seeded the amplifier with the second harmonic of a Ti:sapphire laser.
• Measured pulse energy and spectral distributions of harmonics up to the 11th order.
• Compared experimental results with theoretical simulations.

Main Results:

• Successfully observed higher order harmonic generation in the superradiant FEL.
• Superradiance was effectively induced at seed intensities near FEL saturation.
• Measured harmonics up to the 11th order, showing good agreement with simulations.

Conclusions:

• Demonstrated the feasibility of generating higher order harmonics in a superradiant FEL.
• Seeding is an effective method to control and enhance superradiance in FELs.
• The findings provide insights into nonlinear processes in high-gain FELs.