Browsing by Author "Kriesel, Jason M."

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    Low-loss and single-mode tapered hollow-core waveguides optically coupled with interband and quantum cascade lasers
    (SPIE, 2018) Giglio, Marilena; Patimisco, Pietro; Sampaolo, Angelo; Kriesel, Jason M.; Tittel, Frank K.; Spagnolo, Vincenzo
    We report single-mode midinfrared laser beam delivery through a 50-cm-long tapered hollow-core waveguide (HCW) having bore diameter linearly increasing from 200 to 260  μm. We performed theoretical calculations to identify the best HCW-laser coupling conditions in terms of optical losses and single-mode fiber output. To validate our modeling, we coupled the HCW with an interband cascade laser and four quantum cascade lasers with their emission wavelengths spanning 3.5 to 7.8  μm, using focusing lenses with different focal lengths. With the best coupling conditions, we achieved single-mode output in the investigated 3.5 to 7.8  μm spectral range, with minimum transmission losses of 1.27 dB at 6.2  μm.
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    Single mode operation with mid-IR hollow fibers in the range 5.1-10.5 µm
    (The Optical Society, 2015) Sampaolo, Angelo; Patimisco, Pietro; Kriesel, Jason M.; Tittel, Frank K.; Scamarcio, Gaetano; Spagnolo, Vincenzo
    Single mode beam delivery in the mid-infrared spectral range 5.1-10.5 μm employing flexible hollow glass waveguides of 15 cm and 50 cm lengths, with metallic/dielectric internal layers and a bore diameter of 200 μm were demonstrated. Three quantum cascade lasers were coupled with the hollow core fibers. For a fiber length of 15 cm, we measured losses down to 1.55 dB at 5.4 μm and 0.9 dB at 10.5 μm. The influence of the launch conditions in the fiber on the propagation losses and on the beam profile at the waveguide exit was analyzed. At 10.5 µm laser wavelength we found near perfect agreement between measured and theoretical losses, while at ~5 µm and ~6 µm wavelengths the losses were higher than expected. This discrepancy can be explained considering an additional scattering loss effect, which scales as 1/λ2 and is due to surface roughness of the metallic layer used to form the high-reflective internal layer structure of the hollow core waveguide.