Continuous-wave modulation of a femtosecond oscillator using coherent molecules

Area of Science:

• Quantum Optics
• Laser Physics
• Molecular Spectroscopy

Background:

• Femtosecond lasers are crucial tools in various scientific fields.
• Broadening the frequency spectrum of lasers is essential for advanced applications.
• Existing spectral broadening techniques often have limitations in efficiency or applicability.

Purpose of the Study:

• To introduce a new method for broadening the frequency spectrum of a femtosecond laser in the continuous-wave (CW) domain.
• To demonstrate a CW optical modulator based on four-wave mixing in a Raman-based system.
• To achieve significant spectral broadening of a Ti:sapphire laser spectrum.

Main Methods:

• Utilizing four-wave mixing (FWM) within a Raman-based optical modulator.
• Preparing the modulator by containing deuterium molecules in a high-finesse optical cavity.
• Driving the fundamental vibrational transition of deuterium molecules with pump and Stokes lasers locked to cavity modes.
• Modulating a femtosecond laser passing through the prepared molecular system in a single pass.

Main Results:

• Demonstrated a CW optical modulator operating at 90 THz.
• Achieved a steady-state single-pass efficiency of approximately 10⁻⁶.
• Obtained a transient single-pass efficiency of approximately 10⁻⁴ on a 10 μs timescale.
• Broadened the spectrum of a Ti:sapphire laser (800 nm) to include upshifted (650 nm) and downshifted (1.04 μm) sidebands.

Conclusions:

• The developed method effectively broadens the frequency spectrum of femtosecond lasers in the CW domain.
• The Raman-based optical modulator offers efficient spectral modulation for optical lasers.
• This technique provides a versatile tool for generating new spectral components and enhancing laser capabilities.