Passive, controllable generation of energetic multi-color pulses via spatial mode re-organizations in optical fibers

H B Kabagöz,S Ramachandran,A Antikainen

doi:10.1063/5.0063447

Abstract

Multi-color energetic pulses of fs pulse width are of interest to applications such as mid-IR wavelength generation via difference frequency generation, nonlinear microscopy, and high harmonic generation. Traditional fiber-based methods to create such sources suffer from group velocity dispersion, which prevents different colors of a mode to be temporally coincident, as well as the timing jitter due to usual perturbations, such as changes in the refractive index of the fiber or slight variations of the pump power. We employ a multi-mode system, which allows group velocity matching of different modes over a Raman shift, hereby circumventing both of these issues by allowing the ultrafast Raman scattering mechanism soliton-self mode conversion (SSMC) to create multiple colors of distinct spatial modes from a single pump pulse. We experimentally demonstrate fiber-based generation of three- and four-color time-synchronized pulses of nJ-level pulse energies and ∼100 fs pulse widths, where the former span ∼25 THz and the latter ∼35 THz.

Highlights

IntroductionEnergetic ultrashort (fs) pulse width sources emitting a variety of user-defined colors with temporal and spatial synchronicity are the mainstays for applications as diverse as pump–probe spectroscopy, mid-IR wavelength generation, multimodal microscopy, and high-harmonic generation, among others
Energetic ultrashort pulse width sources emitting a variety of user-defined colors with temporal and spatial synchronicity are the mainstays for applications as diverse as pump–probe spectroscopy,1,2 mid-IR wavelength generation,3 multimodal microscopy,4,5 and high-harmonic generation,6 among others
When the input pulse energy is increased gradually, we see that the pump mode of LP0,17 first converts itself to the LP0,16 mode through conventional soliton self-mode conversion, which creates the LP0,15 mode through Soliton Self-Mode Conversion (SSMC) as well

Summary

Introduction

Energetic ultrashort (fs) pulse width sources emitting a variety of user-defined colors with temporal and spatial synchronicity are the mainstays for applications as diverse as pump–probe spectroscopy, mid-IR wavelength generation, multimodal microscopy, and high-harmonic generation, among others. Prominent examples of energetic ultrashort-pulse frequency conversion with fibers include Soliton Self-frequency Shifting (SSFS), parametric oscillation, and recently, self-phase modulation (SPM) enabled spectral selection (SESS).. Prominent examples of energetic ultrashort-pulse frequency conversion with fibers include Soliton Self-frequency Shifting (SSFS), parametric oscillation, and recently, self-phase modulation (SPM) enabled spectral selection (SESS).9 These techniques have achieved moderate levels of success in yielding dual-color sources, but making this a scalable platform to achieve on-demand, multiple colors has not been possible. Fiber propagation involves long transmission lengths, over which temperature, stress, or even pump power fluctuations result in temporal jitter of the nonlinearly converted pulse.10 This temporal jitter can be larger than the pulse width, especially for ∼100-fs pulses, yielding completely temporally unsynchronized pulses, defeating the goal of realizing multicolor single-aperture sources Fiber propagation involves long transmission lengths, over which temperature, stress, or even pump power fluctuations result in temporal jitter of the nonlinearly converted pulse. This temporal jitter can be larger than the pulse width, especially for ∼100-fs pulses, yielding completely temporally unsynchronized pulses, defeating the goal of realizing multicolor single-aperture sources

Methods

Results

Conclusion