High-power femtosecond Raman frequency shifter

Area of Science:

• Optics and Photonics
• Nonlinear Optics
• Laser Physics

Background:

• Femtosecond laser technology is crucial for advanced scientific research.
• Generating high-energy pulses in the mid-infrared spectrum presents significant challenges.
• Stimulated Raman scattering (SRS) is a powerful nonlinear optical process for frequency conversion.

Purpose of the Study:

• To generate broadband, high-energy femtosecond pulses centered at 1.28 μm.
• To utilize SRS in a pressurized hydrogen cell for efficient frequency shifting.
• To characterize the performance of the generated pulses for potential applications.

Main Methods:

• Employing two chirped and delayed pulses from a Ti:sapphire amplifier to initiate SRS.
• Using a pressurized hydrogen gas cell as the nonlinear medium.
• Recompressing the Stokes pulse using a reflective grating pair to achieve short pulse durations.

Main Results:

• Achieved record-high Stokes pulse energy of 4.4 mJ.
• Generated broadband femtosecond pulses with a center wavelength of 1.28 μm.
• Recompressed the pulses to a duration of 66 fs.
• Characterized energy stability, beam profile, and conversion efficiency at 100 Hz and 10 Hz repetition rates.

Conclusions:

• The demonstrated high-energy frequency shifter is a significant advancement in ultrafast optics.
• The generated pulses are suitable for driving intense terahertz (THz) sources.
• This technology has potential applications in materials science, spectroscopy, and nonlinear THz generation.