A high-performance 4-bit optical true time delay device is realized on a perfluoropolymer integrated optic platform. The integrated waveguide circuit is based on athermal arrayed wavegide grating with monolithically integrated delay lines in a wavelength-selective recirculating loop configuration. The device provides precise delay length control (i.e., 1 m) over 16 channels with 40-ps incremental time delays. The device offers athermal operation over the 0 C-50 C range with a maximum insertion loss of 6.8 dB and a polarization shift of 0.4 nm. This compact device mm promises applications in code-division multiple access and phased arrayed antenna systems, where the large channel counts with high resolution delay length controls and small footprints are required.
We fabricate single-mode polymer waveguide structures exhibiting polarization-independent ultra-low loss of 0.04 and 0.05 dB/cm at the 1310 and 1550 nm bands, respectively, with a Deltan of 1.6%. A porous structure that arises during the fabrication process is studied by considering its implications in the propagation loss based on the Rayleigh-Mie scattering loss mechanism. We demonstrate that the porous structure is to be reduced to the nanoscale (i.e., <10 nm) to realize waveguide structures with ultra-low propagation losses based on fabrications and measurements of morphologies with various degrees of porosity. Further, the bending loss and its respective polarization-dependent propagation loss behavior are analyzed to realize compact devices with ultra-low-loss and polarization-independent features, where a 4 mm bending radius is found to be adequate for such a performance over the 1550 nm band.
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