Giglio, MarilenaPatimisco, PietroSampaolo, AngeloKriesel, Jason M.Tittel, Frank K.Spagnolo, Vincenzo2017-09-192017-09-192018Giglio, Marilena, Patimisco, Pietro, Sampaolo, Angelo, et al.. "Low-loss and single-mode tapered hollow-core waveguides optically coupled with interband and quantum cascade lasers." <i>Optical Engineering,</i> 57, no. 1 (2018) SPIE: https://doi.org/10.1117/1.OE.57.1.011004.https://hdl.handle.net/1911/97408We 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.engArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.Journal articleLow-loss_single-mode_tapered_hollow-core_waveguideshttps://doi.org/10.1117/1.OE.57.1.011004