In Situ Fabrication of Far-Detuned Mid-Infrared Optical Fiber Wavelength Converters

Chalcogenide (ChG) glasses have been identified as promising materials for applications in nonlinear photonics due to their exceptionally high nonlinear refractive index; nearly three orders of magnitude beyond that of silica glass. A ChG fiber or waveguide that is tapered down into a microwire provides strong light confinement and enhanced nonlinear optical effect, it allows engineerable chromatic dispersion and thereby an easy access to nonlinear parametric processes such as four-wave mixing (FWM). In well-controlled conditions of chromatic dispersion ChG microwires may lead to strong parametric gain that is far-detuned with respect to the pump wavelength, by tens of THz [1,2], In theory, chromatic dispersion in a waveguide is precisely adjusted from a good control of waveguide geometry. In practice however, the amount of precision required in waveguide geometry as well as errors on the evaluation of refractive indices prevent the fabrication of wavelength converters with a predetermined wavelength offset. To illustrate this, fig. 1(a) shows the theoretical spectrum of a far-detuned ChG wavelength converter. A change in the core diameter by 5 mn results in a ~ 40 mn wavelength shift of the parametric sidebands. As an element of solution inspired from past reports, it has been shown with supercontinuum generation that experimental parameters could be finely tuned using an in situ monitoring technique [3], In this work, we demonstrate that wavelength conversion of a ChG microwire is precisely attained by in situ tracking of the microwire output during the tapering process, enabling the fabrication of wavelength converters that are precisely far-detuned by at least 34.3 THz.