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Proceedings Paper

Designing silicon-core fiber tapers for efficient mid-IR supercontinuum generation (Conference Presentation)
Author(s): Joseph Campling; Anna C. Peacock; Peter Horak

Paper Abstract

We propose a taper design for a silicon-core fiber for the purpose of generating a supercontinuum (SC) from a 2.1μm pulsed fiber laser. The design is tailored to maximise the conversion efficiency (CE) to the 3-4μm region, which is important for environmental sensing as it includes several key greenhouse gas absorption lines. There is a need for compact, low-power and efficient solutions. Aluminium nitride photonic-chip waveguides have been shown to generate 0.3mW in the 3-4μm region with an 80mW input. Although this is sufficient power for some applications, the system only offers a 0.4% CE. More recently a silicon nitride planar waveguide was used to transfer energy from a commercial 2.1μm femtosecond laser to targeted wavelengths in the 3-4μm region through dispersive wave generation. To cover the entire region, it is estimated that an input of 40mW would be needed to generate ~1mW (CE of 2.5%). Compared to these materials silicon has a higher nonlinearity and, despite multi-photon absorption, is highly efficient at transferring energy to different wavelengths with modest input powers. Moreover, silicon-core fibers can be tapered using established post-processing procedures, which can be used to control the phase-matching conditions to concentrate energy in a required wavelength range. We have designed a silicon-core fiber taper that can take the input from a 2.1μm fiber laser and efficiently transfer the energy to cover the entire 3-4μm range. We simulated SC generation using the generalised nonlinear Schrödinger equation including wavelength-dependent loss terms (linear, TPA and 3PA). From these simulations we estimate that ~0.8mW average power can be generated covering the entire 3-4μm region, with only 15mW input power, a CE of 5%.

Paper Details

Date Published: 1 April 2020
Proc. SPIE 11358, Nonlinear Optics and its Applications 2020, 113580E (1 April 2020); doi: 10.1117/12.2555810
Show Author Affiliations
Joseph Campling, Univ. of Southampton (United Kingdom)
Anna C. Peacock, Univ. of Southampton (United Kingdom)
Peter Horak, Univ. of Southampton (United Kingdom)

Published in SPIE Proceedings Vol. 11358:
Nonlinear Optics and its Applications 2020
Neil G. R. Broderick; John M. Dudley; Anna C. Peacock, Editor(s)

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