Source: http://aoot.osa.org/oe/abstract.cfm?uri=oe-23-5-6903
Timestamp: 2019-04-21 18:27:35+00:00

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We numerically investigate mid-infrared supercontinuum (SC) generation in dispersion-engineered, air-clad, Ge11.5As24Se64.5 chalcogenide-glass channel waveguides employing two different materials, Ge11.5As24S64.5 or MgF2 glass for their lower cladding. We study the effect of waveguide parameters on the bandwidth of the SC at the output of 1-cm-long waveguide. Our results show that output can vary over a wide range depending on its design and the pump wavelength employed. At the pump wavelength of 2 μm the SC never extended beyond 4.5 μm for any of our designs. However, supercontinuum could be extended to beyond 5 μm for a pump wavelength of 3.1 μm. A broadband SC spanning from 2 μm to 6 μm and extending over 1.5 octave could be generated with a moderate peak power of 500 W at a pump wavelength of 3.1 μm using an air-clad, all-chalcogenide, channel waveguide. We show that SC can be extended even further when MgF2 glass is used for the lower cladding of chalcogenide waveguide. Our numerical simulations produced SC spectra covering the wavelength range 1.8–7.7 μm (> two octaves) by using this geometry. Both ranges exceed the broadest SC bandwidths reported so far. Moreover, we realize it using 3.1 μm pump source and relatively low peak power pulses. By employing the same pump source, we show that SC spectra can cover a wavelength range of 1.8–11 μm (> 2.5 octaves) in a channel waveguide employing MgF2 glass for its lower cladding with a moderate peak power of 3000 W.
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Fig. 2 GVD curves for the fundamental quasi-TE mode calculated from neff for three waveguides geometries employing As36S64 glass for both the upper and lower claddings. The black solid line curve shows the material dispersion curve for comparison.
Fig. 3 GVD curves for the waveguide geometries employing two different lower claddings (solid black curve for Ge11.5As24S64.5 and red dashed curve for MgF2) for the fundamental quasi-TE mode (a) at a pump wavelength of 2 μm and (b) at a pump wavelength of 3.1 μm. Vertical dotted line indicates the position of pump wavelength.
Fig. 4 Simulated SC spectra at a pump wavelength of 2 μm for (a) air-clad all-chalcogenide waveguide at peak power from 25, 100, and 500 W; (b) air-clad chalcogenide core employing MgF2 for its lower cladding at the same power levels; (c) waveguides with two different lower claddings at a peak power of 500 W only.
Fig. 5 Spectral evolution along the waveguide length corresponding to Fig. 4(c).
Fig. 6 Simulated SC spectra at a pump wavelength of 3.1 μm for (a) air-clad allchalcogenide waveguide at peak power between 100 W and 3000 W; (b) air-clad chalcogenide core employing MgF2 for its lower cladding for the same power levels; (c) waveguides employing with two different lower claddings at a peak power of 500 W only; (d) waveguides with two different lower claddings at peak power of 3000 W only.
Fig. 7 Spectral evolution along the waveguide length corresponding to Fig. 6(c) (left column) and 6(d) (right column), respectively.

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