61 research outputs found
Broadband directional coupling in aluminum nitride nanophotonic circuits
Aluminum nitride (AlN)-on-insulator has emerged as a promising platform for
the realization of linear and non-linear integrated photonic circuits. In order
to efficiently route optical signals on-chip, precise control over the
interaction and polarization of evanescently coupled waveguide modes is
required. Here we employ nanophotonic AlN waveguides to realize directional
couplers with a broad coupling bandwidth and low insertion loss. We achieve
uniform splitting of incoming modes, confirmed by high extinction-ratio
exceeding 33dB in integrated Mach-Zehnder Interferometers. Optimized
three-waveguide couplers furthermore allow for extending the coupling bandwidth
over traditional side-coupled devices by almost an order of magnitude, with
variable splitting ratio. Our work illustrates the potential of AlN circuits
for coupled waveguide optics, DWDM applications and integrated polarization
diversity schemes
Diamond Integrated Optomechanical Circuits
Diamond offers unique material advantages for the realization of micro- and
nanomechanical resonators due to its high Young's modulus, compatibility with
harsh environments and superior thermal properties. At the same time, the wide
electronic bandgap of 5.45eV makes diamond a suitable material for integrated
optics because of broadband transparency and the absence of free-carrier
absorption commonly encountered in silicon photonics. Here we take advantage of
both to engineer full-scale optomechanical circuits in diamond thin films. We
show that polycrystalline diamond films fabricated by chemical vapour
deposition provide a convenient waferscale substrate for the realization of
high quality nanophotonic devices. Using free-standing nanomechanical
resonators embedded in on-chip Mach-Zehnder interferometers, we demonstrate
efficient optomechanical transduction via gradient optical forces. Fabricated
diamond resonators reproducibly show high mechanical quality factors up to
11,200. Our low cost, wideband, carrier-free photonic circuits hold promise for
all-optical sensing and optomechanical signal processing at ultra-high
frequencies
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