Cryogenically cooled Fe:ZnSe-based chirped pulse amplifier at 4.07 µm

Area of Science:

• Laser Physics
• Materials Science
• Quantum Optics

Background:

• Femtosecond laser systems are crucial for advanced scientific research.
• Previous chirped pulse amplifiers faced limitations in repetition rate and operating wavelength.
• The mid-infrared spectrum offers unique advantages for atmospheric transmission and specific material interactions.

Purpose of the Study:

• To demonstrate a femtosecond chirped pulse amplifier operating at a significantly higher repetition rate.
• To utilize a cryogenically cooled Fe:ZnSe gain medium for improved performance.
• To achieve laser output at a wavelength that minimizes atmospheric CO2 absorption.

Main Methods:

• Development of a femtosecond chirped pulse amplifier utilizing a cryogenically cooled Fe:ZnSe crystal.
• Employing diode-pumped Er:YAG lasers as pump sources, leveraging the long upper-state lifetime of the gain medium.
• Characterization of amplified pulse energy, duration, wavelength, and beam quality.

Main Results:

• Demonstrated a repetition rate of 333 Hz, a 33-fold increase over near-room-temperature systems.
• Produced 250-fs pulses with 4.59-mJ energy at a 4.07 µm center wavelength.
• Achieved good beam quality and observed up to ninth-order harmonics when focusing the 18-GW beam in air.

Conclusions:

• Cryogenic cooling of Fe:ZnSe is effective for achieving high-repetition-rate femtosecond amplification.
• The 4.07 µm output enables operation in ambient air, avoiding CO2 absorption bands.
• The high peak power and unique wavelength make the system suitable for strong-field experimentation and atmospheric sensing.