Tailoring frequency generation in uniform and concatenated multimode fibers

Area of Science:

• Nonlinear Optics
• Fiber Optics
• Laser Physics

Background:

• Multimode parabolic-index fibers offer unique light propagation properties.
• Nonlinear frequency generation is crucial for developing novel optical sources.
• Controlling parametric instabilities is key to precise frequency engineering.

Purpose of the Study:

• To demonstrate precise engineering of frequency generation in multimode parabolic-index fibers.
• To investigate the role of fiber core size and cascading on nonlinear frequency generation.
• To validate experimental findings with analytical predictions and numerical simulations.

Main Methods:

• Utilizing amplified Q-switched microchip laser (400 ps pulses at 1064 nm).
• Analyzing nonlinear frequency generation in fibers with varying core sizes (50, 60, 80 μm).
• Employing fiber cascading of different core sizes to achieve desired frequency bands.

Main Results:

• Observed intense frequency sidebands dependent on fiber core size.
• Demonstrated precise engineering of frequency generation through fiber design.
• Achieved desired frequency bands by cascading fibers of different core sizes.
• Experimental results showed good agreement with analytical predictions and numerical simulations.

Conclusions:

• Fiber core scaling and concatenation are effective strategies for designing optical sources.
• Geometric parametric instability is a key mechanism for engineered frequency generation.
• This approach enables the development of optical sources with tailored output frequencies.