Sub-40 fs optical parametric oscillator beyond the gain bandwidth limit.

Area of Science:

• Nonlinear Optics
• Ultrafast Lasers
• Fiber Optics

Background:

• Generating ultrashort optical pulses is crucial for various scientific and technological applications.
• Existing methods often face limitations in pulse duration, stability, or system compactness.
• Optical parametric oscillators (OPOs) offer a versatile platform for wavelength conversion and pulse generation.

Purpose of the Study:

• To develop a compact and passively stable optical parametric oscillator (OPO).
• To achieve direct generation of ultrashort pulses significantly shorter than the pump laser.
• To demonstrate broadband spectral coverage with high power and spectral stability.

Main Methods:

• Utilized an intracavity all-normal dispersion feedback fiber within the OPO.
• Employed nonlinear spectral broadening beyond the parametric gain bandwidth.
• Characterized pulse duration, spectral coverage, power stability, and spectral stability.

Main Results:

• Generated sub-40 femtosecond (fs) pulses, five times shorter than the 200 fs pump.
• Achieved low-noise and coherent spectral broadening beyond the parametric gain bandwidth.
• Demonstrated spectral coverage from 1.1 to 2.0 µm with <0.1% rms power and spectral stability.
• The OPO system has a compact footprint (<14x14 cm²).

Conclusions:

• The developed compact OPO provides a stable and efficient method for generating ultrashort pulses.
• Intracavity all-normal dispersion fiber enables significant pulse compression and spectral broadening.
• This technology is suitable for applications requiring stable, broadband, ultrashort light sources.