Periodic structures with dimensions
on the order of the wavelength of light can tailor and improve the
performance of optical components, and they can enable the creation
of devices with new functionalities. For example, distributed Bragg
reflectors (DBRs), which are created by periodic modulations in a
structure’s dielectric medium, are essential in dielectric
mirrors, vertical cavity surface emitting lasers, fiber Bragg gratings,
and single-frequency laser diodes. This work introduces nanoscale
DBRs integrated directly into gallium nitride (GaN) nanowire waveguides.
Photonic band gaps that are tunable across the visible spectrum are
demonstrated by precisely controlling the grating’s parameters.
Numerical simulations indicate that in-wire DBRs have significantly
larger reflection coefficients in comparison with the nanowire’s
end facet. By comparing the measured spectra with the simulated spectra,
the index of refraction of the GaN nanowire waveguides was extracted
to facilitate the design of photonic coupling structures that are
sensitive to phase-matching conditions. This work indicates the potential
to design nanowire-based devices with improved performance for optical
resonators and optical routing
