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Abstract: We report two novel fabrication techniques, as well as spectral transmissionand propagation loss measurements of the subwavelength plastic wires withhighly porous up to 86% and non-porous transverse geometries. The twofabrication techniques we describe are based on the microstructured moldingapproach. In one technique the mold is made completely from silica by stackingand fusing silica capillaries to the bottom of a silica ampoule. The meltedmaterial is then poured into the silica mold to cast the microstructuredpreform. Another approach uses microstructured mold made of plastic which isco-drawn with a cast preform. Material of the mold is then dissolved afterfiber drawing. We also describe a novel THz-TDS setup with an easily adjustableoptical path length, designed to perform cutback measurements using THz fibersof up to 50 cm in length. We find that while both porous and non-poroussubwavelength fibers of the same outside diameter have low propagation losses\alpha \leg 0.02cm-1, however, the porous fibers exhibit a much widerspectral transmission window and enable transmission at higher frequenciescompared to the non-porous fibers. We then show that the typical bell-shapedtransmission spectra of the subwavelengths fibers can be very well explained bythe onset of material absorption loss at higher frequencies due to strongconfinement of the modal fields in the material region of the fiber, as well asstrong coupling loss at lower frequencies due to mismatch of the modal fielddiameter and a size of the gaussian-like beam of a THz source.



Author: A. Dupuis, A. Mazhorova, F. Desevedavy, M. Rosé, M. Skorobogatiy

Source: https://arxiv.org/







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