Tapered silicon core fibres for supercontinuum generation

Abstract

A series of silicon-core fibre tapers are designed that allow for longitudinal variation of their nonlinear and dispersion parameters with length. A supercontinuum (SC) is generated in the waist region of the taper due to the increased nonlinearity there. The long-wavelength edge of the SC is then boosted by up-tapering to a specific core diameter which is chosen to optimise the phase-matching conditions for four-wave mixing. This means that the bulk of the initially-generated SC can be used as pump sources for transferring power to the long-wavelength edge. Each design targets a specific wavelength range with a 0.25 µm bandwidth. The design work is driven by simulations of mid-infrared laser pulse propagation through the fibres, which work by solving the generalised nonlinear Schrödinger equation (GNLSE). This incorporates numerous nonlinear effects in silicon affecting SC generation, including two-photon absorption (TPA), three-photon absorption and free-carrier effects. The wavelength-dependence of linear loss and the effective area of the fundamental mode is incorporated into the GNLSE, which is extended to also incorporate the wavelength-dependence of TPA. The possibility of using these taper design principles is also explored for silicon on-insulator waveguides.

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Identifiers

ORCID for Anna Peacock: orcid.org/0000-0002-1940-7172

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