All-Normal-Dispersion Chalcogenide Waveguides for Ultraflat Supercontinuum Generation in the Mid-Infrared Region

We show numerically, how a chalcogenide planar waveguide designed to exhibit normal dispersion over a wide spectral range around the pump wavelength can produce relatively flat supercontinuum in the mid-infrared regime. A 1-cm-long channel waveguide, made using Ge<sub>11.5</sub>As<sub>24</sub>Se<sub>64.5</sub> glass and pumped at 1.55 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> using short optical pulses with only 25 W peak power, produced a supercontinuum that was nearly 600 nm wide. Employing the same pump source with a peak power of 100 W, the supercontinuum could be extended to beyond 2.2 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> with a bandwidth of 1000 nm. By shifting the pump wavelength to 3.1 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> and using pulses with peak powers of up to 3 kW, the resulting ultraflat supercontinuum extended from 2 to <inline-formula> <tex-math notation="LaTeX">$5.5~\mu \text{m}$ </tex-math></inline-formula>. Even a wider spectral range (1.8-6 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula>) can be realized if MgF<sub>2</sub> glass is used for the lower cladding while maintaining power variations below 5 dB over the entire bandwidth.

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