Self-aligned micro-optic integrated photonic platform.

In this work, we present the fabrication technology of a monolithically integrated photonic platform combining key components for optical coherence tomography (OCT) imaging, thereby including a photonic interferometer, a collimating lens, and a 45° reflecting mirror that directs the light from the interferometer to the collimator. The proposed integration process simplifies the fabrication of an interferometric system and inherently overcomes the complexity of costly alignment procedures while complying with the necessarily stringent optical constraints. Fabricated waveguide characterization shows total optical losses as low as 3 dB, and less than 1 dB of additional loss due to the Si 45° mirror facet. The alignment standard deviation of all components is within 15 nm. The integrated lens profile achieves a divergence angle smaller than 0.7°, which is close to that of a collimator. The proposed photonic platform provides the premise for low-cost and small-footprint single-chip OCT systems.

Effects of Conformal Nanoscale Coatings on Thermal Performance of Vertically Aligned Carbon Nanotubes.

The high aspect ratio and the porous nature of spatially oriented forest-like carbon nanotube (CNT) structures represent a unique opportunity to engineer a novel class of nanoscale assemblies. By combining CNTs and conformal coatings, a 3D lightweight scaffold with tailored behavior can be achieved. The effect of nanoscale coatings, aluminum oxide (Al2 O3 ) and nonstoichiometric amorphous silicon carbide (a-SiC), on the thermal transport efficiency of high aspect ratio vertically aligned CNTs, is reported herein. The thermal performance of the CNT-based nanostructure strongly depends on the achieved porosity, the coating material and its infiltration within the nanotube network. An unprecedented enhancement in terms of effective thermal conductivity in a-SiC coated CNTs has been obtained: 181% compared to the as-grown CNTs and Al2 O3 coated CNTs. Furthermore, the integration of coated high aspect ratio CNTs in an epoxy molding compound demonstrates that, next to the required thermal conductivity, the mechanical compliance for thermal interface applications can also be achieved through coating infiltration into foam-like CNT forests.