Study of broadband multimode light via non-phase-matched sum frequency generation

TL;DR

This paper introduces non-phase-matched sum frequency generation as a novel technique for characterizing broadband multimode light, demonstrating its advantages in efficiency and mode sensitivity using high-gain PDC.

Contribution

It presents a new method for broadband multimode light characterization that avoids phase matching, enhancing efficiency and mode sensitivity analysis.

Findings

Increased SFG efficiency by generating sum frequency near the crystal surface.

Elimination of Maker fringes due to chromatic dispersion effects.

Successful non-phase-matched three- and four-frequency summation of broadband light.

Abstract

We propose non-phase-matched sum frequency generation (SFG) as a method for characterizing broadband multimode light. We demonstrate its advantages using high-gain parametric down conversion (PDC) as an example. By generating the sum frequency in the near-surface region of a nonlinear crystal, we increase the SFG efficiency and get rid of the modulation caused by chromatic dispersion, known as Maker fringes. The obtained results interpreted in terms of the Schmidt mode formalism reveal the sensitivity of the SFG spectrum to the number of frequency modes. Furthermore, we demonstrate efficient non-phase-matched three- and four-frequency summation of broadband multimode light, barely possible under phase matching.