Intermodal group-velocity engineering for broadband nonlinear optics

Abstract

Interest in the nonlinear properties of multi-mode optical waveguides has seen a recent resurgence on account of the large dimensionality afforded by the platform. However, a perceived fundamental limitation of intermodal parametric interactionsthat they are impractically narrowbandhas yet to be solved. Here we show that by engineering the relative group velocity within the discrete spatial degree of freedom, we can tailor the phase matching bandwidth of intermodal parametric nonlinearities. We demonstrate group-velocitytailored four-wave mixing between the LP0,4 and LP0,5 modes of a multi-mode fiber with unprecedented gain bandwidths (>60 nm at ~1550 nm). As evidence of the technological utility of this methodology, we seed this process to generate a high-peak-power wavelength-tunable fiber laser in the Ti:Sapphire wavelength regime. More generally, with the combination of intermodal interactions, which dramatically expand the phase matching degrees of freedom for nonlinear optics, and intermodal group velocity engineering, which enables tailoring the bandwidth of such interactions, we showcase a platform for nonlinear optics that can be broadband while being wavelength agnostic.

Multimode optically adiabatic silica glass submicron taper

“…The unique capability of our MAST to adiabatically transmit several HOMs simultaneously, combined with all-fiber devices that perform the near-unity-efficiency in-fiber mode conversion between the LP01 mode and the HOM (at least the LP11, LP21, and LP02 modes), offers a variety of intriguing opportunities in the emerging field of multimode nonlinear optics and quantum optics. Novel multimode nonlinear optical frequency conversion [43] and nonclassical light generation [22,23,25], multimode photonic quantum information processing [44,45], and broadband spatiotemporal dynamics [46] can be investigated with high efficiencies in all-fiber platforms. Furthermore, manipulation of the evanescent field profiles can be facilitated through excitation of HOMs in the MAST waist for tailoring the optical trapping potentials of atoms and nanoparticles [47].…”

Polarization-entangled photon pairs in the visible spectral band using intermodal spontaneous four-wave mixing

“…23,24,29,35,36 The other approach is based on the multimode and/or fewmode waveguide structure via intermodal SFWM (IM-SFWM). [37][38][39] IM-SFWM could generate photon pairs far from the pump frequency due to the phase-matching mechanism with the difference dispersion properties of different spatial modes of the multi-or few-mode waveguide. There have been several theoretical investigation and successful demonstration of photon pair source via IM-SFWM in step-index fiber, [40][41][42] graded-index fiber, 43 and polarization maintaining fiber.…”

Optical fiber polarization-entangled photon pair source using intermodal spontaneous four-wave mixing in the visible spectral band

“…Studies of entangled photon pair source in birefringent optical fiber have been extensively conducted at various wavelength region [29,30,35,41,42]. The other approach is based on the multimode and/or few-mode waveguide structure via intermodal SFWM (IM-SFWM) [43][44][45]. IM-SFWM could generate photon pairs far from the pump frequency due to the phasematching mechanism with the difference dispersion properties of different spatial modes of the multi-or few-mode waveguide.…”