Cavity-dumping a single infrared pulse from a free-electron laser for two-color pump-probe experiments

Area of Science:

• Physics
• Materials Science
• Spectroscopy

Background:

• Mid- to far-infrared electromagnetic radiation is crucial for studying collective excitations in solids and molecules.
• Generating short, intense pulses in the terahertz range is challenging.
• Free-electron lasers offer tunability but typically produce lower-energy pulses (microjoules).

Purpose of the Study:

• To demonstrate a novel setup for generating high-energy, picosecond-long mid- to far-infrared pulses.
• To establish a two-color pump-probe system for time-resolved magnetization dynamics studies.
• To showcase the system's capability in observing ultrafast magnetic phenomena.

Main Methods:

• Utilizing cavity-dumping with a free-electron laser to produce single, picosecond pulses.
• Varying pulse duration through cavity detuning.
• Implementing a two-color pump-probe spectroscopy setup with the generated infrared pulses.
• Performing single-shot time-resolved imaging.

Main Results:

• Successfully generated single, picosecond-long mid- to far-infrared pulses with energies exceeding 100 µJ.
• Demonstrated the capability for single-shot time-resolved imaging of magnetization dynamics.
• Observed thermally induced demagnetization and magnetic switching in GdFeCo thin films.
• Showcased time-resolved detection of resonant phononic switching in magnetic garnets.

Conclusions:

• The developed cavity-dumping free-electron laser setup provides a powerful tool for generating high-energy, tunable infrared pulses.
• This technique significantly advances the study of ultrafast magnetization dynamics and other light-matter interactions.
• The system enables unprecedented single-shot, time-resolved investigations of magnetic phenomena.