Patimisco, PietroSampaolo, AngeloMihai, LauraGiglio, MarilenaKriesel, JasonSporea, DanScamarcio, GaetanoTittel, Frank K.Spagnolo, Vincenzo2016-04-292016-04-292016Patimisco, Pietro, Sampaolo, Angelo, Mihai, Laura, et al.. "Low-Loss Coupling of Quantum Cascade Lasers into Hollow-Core Waveguides with Single-Mode Output in the 3.7–7.6 μm Spectral Range." <i>Sensors,</i> 16, no. 4 (2016) MDPI: http://dx.doi.org/10.3390/s16040533.https://hdl.handle.net/1911/90376We demonstrated low-loss and single-mode laser beam delivery through hollow-core waveguides (HCWs) operating in the 3.7–7.6 μm spectral range. The employed HCWs have a circular cross section with a bore diameter of 200 μm and metallic/dielectric internal coatings deposited inside a glass capillary tube. The internal coatings have been produced to enhance the spectral response of the HCWs in the range 3.5–12 µm. We demonstrated Gaussian-like outputs throughout the 4.5–7.6 µm spectral range. A quasi single-mode output beam with only small beam distortions was achieved when the wavelength was reduced to 3.7 μm. With a 15-cm-long HCW and optimized coupling conditions, we measured coupling efficiencies of >88% and transmission losses of <1 dB in the investigated infrared spectral range.engThis is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Journal articlesingle-mode outputhollow-core waveguidequantum cascade laseroptical couplinghttp://dx.doi.org/10.3390/s16040533