[Paper Review] Wave-front shaping in nonlinear multimode fibers

Omer Tzang, Antonio M. Caravaca-Aguirre+2 more|arXiv (Cornell University)|Jan 18, 2017

Random lasers and scattering media60 references3 citations

TL;DR

This paper demonstrates wave-front shaping in nonlinear multimode fibers using a spatial light modulator and genetic algorithm optimization to control complex nonlinear interactions, including stimulated Raman scattering and four-wave mixing. The authors achieve versatile spectral engineering—shifting, suppressing, and enhancing Stokes and anti-Stokes peaks—through implicit mode superposition control, marking a significant advance in nonlinear light manipulation in multimode systems.

ABSTRACT

Recent remarkable progress in wave-front shaping has enabled control of light propagation inside linear media to focus and image through scattering objects. In particular, light propagation in multimode fibers comprises complex intermodal interactions and rich spatiotemporal dynamics. Control of physical phenomena in multimode fibers and its applications is in its infancy, opening opportunities to take advantage of complex mode interactions. In this work, we demonstrate a wave-front shaping approach for controlling nonlinear phenomena in multimode fibers. Using a spatial light modulator at the fiber input and a genetic algorithm optimization, we control a highly nonlinear stimulated Raman scattering cascade and its interplay with four wave mixing via a flexible implicit control on the superposition of modes that are coupled into the fiber. We show for the first time versatile spectrum manipulations including shifts, suppression, and enhancement of Stokes and anti-Stokes peaks. These demonstrations illustrate the power of wave-front shaping to control and optimize nonlinear wave propagation.

Motivation & Objective

• To explore and demonstrate control over nonlinear wave propagation in multimode fibers, which exhibit complex intermodal interactions.
• To address the challenge of optimizing nonlinear processes such as stimulated Raman scattering and four-wave mixing in multimode fibers.
• To develop a flexible, implicit method for shaping the input wave front to manipulate the superposition of excited modes.
• To enable dynamic and precise spectral control of nonlinear outputs, including Stokes and anti-Stokes peaks.
• To establish a framework for optimizing and tailoring nonlinear optical phenomena in complex, multimode media.

Proposed method

• A spatial light modulator (SLM) is used at the fiber input to shape the wave front of the incident light.
• A genetic algorithm performs iterative optimization to find the optimal phase pattern on the SLM for desired nonlinear output.
• The method enables implicit control over the superposition of multiple fiber modes coupled into the multimode fiber.
• Nonlinear processes such as stimulated Raman scattering and four-wave mixing are coherently excited and manipulated via the tailored mode excitation.
• The system dynamically adjusts the input wave front to optimize the spectral response of the nonlinear output.
• The approach relies on feedback from the output spectrum to guide the optimization process without requiring explicit knowledge of the mode composition.

Experimental results

Research questions

• RQ1 Can wave-front shaping be effectively applied to control nonlinear processes in multimode fibers?
• RQ2 To what extent can the spectral response of stimulated Raman scattering and four-wave mixing be manipulated through mode superposition control?
• RQ3 Can a genetic algorithm optimize the input wave front to achieve desired spectral outcomes in a nonlinear multimode system?
• RQ4 How does the interplay between Raman scattering and four-wave mixing evolve under tailored excitation of fiber modes?
• RQ5 What level of spectral control—such as peak shifting, suppression, or enhancement—can be achieved in a nonlinear multimode fiber environment?

Key findings

• The authors successfully demonstrated dynamic spectral control over nonlinear Raman and four-wave mixing processes in a multimode fiber.
• Stokes and anti-Stokes peaks were shifted, suppressed, and enhanced through optimized wave-front shaping, confirming precise control over nonlinear output spectra.
• The genetic algorithm-based optimization converged to optimal phase patterns that maximized or minimized specific spectral features.
• The method enabled control over the interplay between Raman scattering and four-wave mixing by manipulating the input mode superposition.
• The system achieved high-fidelity spectral engineering without requiring full knowledge of the fiber’s mode structure or propagation dynamics.
• The results show that wave-front shaping can unlock new capabilities in nonlinear optics by exploiting complex mode interactions in multimode fibers.