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Second harmonic generation in multimode graded-index fibers: spatial beam cleaning and multiple harmonic sideband
Optics Letters
|March 2, 2017
Summary
In multimode graded-index fibers, second harmonic generation produces unique sidebands and transforms disordered light into bell-shaped beams as pump power increases.
Area of Science:
- Nonlinear Optics
- Fiber Optics
Background:
- Second harmonic generation (SHG) is a key nonlinear optical process.
- Poled single-mode fibers are typically used for SHG.
Purpose of the Study:
- Investigate the spectral and spatial dynamics of SHG in all-optically poled multimode graded-index fibers.
- Contrast SHG behavior in multimode fibers with that in single-mode fibers.
Main Methods:
- Experimental investigation of SHG.
- Numerical simulations of SHG dynamics.
- Analysis of spectral and spatial properties of light.
Main Results:
- Multimode graded-index fibers exhibit sharp sidebands around the second harmonic (SH).
- These sidebands arise from periodic intensity evolution at the fundamental frequency.
- Increasing pump power alters spatial beam profiles from speckles to bell shapes for both fundamental and SH light.
Conclusions:
- Multimode graded-index fibers offer distinct SHG characteristics compared to single-mode fibers.
- The interplay between fundamental and SH light influences spatial beam formation.
- Controlled spatial beam shaping is achievable through pump power adjustment in these fibers.
