We report mid-infrared supercontinuum generation in a silicon germanium-on-silicon waveguide. We show that, by adding a chalcogenide cladding, it is possible to trim a posteriori the waveguide’s dispersion profile which, in turn, governs the properties of the generated supercontinuum. In particular, we experimentally show that a shift from anomalous to normal dispersion takes place when a 1.26 μm thick cladding layer of Ge11.5As24Se64.5 is added. Finally, we show that the group velocity dispersion of the waveguide can be precisely controlled by changing the thickness of the cladding layer.
We present silicon-germanium on silicon waveguides as a suitable platform for on-chip supercontinuum generation in the mid-infrared. We report low propagation loss (<0.4dB∕cm) in the 3.5-5 μm range, leading to an octave spanning supercontinuum extending up to 8.5 μm with a high average power of more than 10 mW on-chip. Furthermore, we present the addition of a chalcogenide cladding layer as a simple post-processing technique to fine tune the waveguide dispersion which, in turn, governs the properties of the generated supercontinuum.
Photonic integrated circuits are established as the technique of choice for a number of astronomical processing functions due to their compactness, high level of integration, low losses, and stability. Temperature control, mechanical vibration and acoustic noise become controllable for such a device enabling much more complex processing than can realistically be considered with bulk optics. To date the benefits have mainly been at wavelengths around 1550 nm but in the important Mid-Infrared region, standard photonic chips absorb light strongly. Chalcogenide glasses are well known for their transparency to beyond 10000 nm, and the first results from coupler devices intended for use in an interferometric nuller for exoplanetary observation in the Mid-Infrared L’ band (3800-4200 nm) are presented here showing that suitable performance can be obtained both theoretically and experimentally for the first fabricated devices operating at 4000 nm.
We report the fabrication and packaging of 1 by 8 power splitter on BK-7 glass. The single mode waveguide structures at 1.31 and 1.55 micrometers have been fabricated using K+- Ag+-Na+ ion exchange at 340 degrees followed by the reverse ion exchange at the same temperature. The power splitter is first tested on the optical test bench and then fiber pigtailed using an automated alignment system and packaged in a compact housing. The total insertion loss for 1 by 8 power splitter after packaging is 5.6 dB at 1.31 micrometers and 4.8 dB at 1.55 micrometers wavelength. The uniformity of power in the output ports is < 1.5 dB while the directivity is measured to be > 40 dB.
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