26 research outputs found
Bound-state-in-continuum guided modes in a multilayer electro-optically active photonic integrated circuit platform
Bound states in the continuum (BICs) are localized states existing within a
continuous spectrum of delocalized waves. Emerging multilayer photonic
integrated circuit (PIC) platforms allow implementation of low index 1D guided
modes within a high-index 2D slab mode continuum; however, conventional wisdom
suggests that this always leads to large radiation losses. Here we demonstrate
low-loss BIC guided modes for multiple mode polarizations and spatial orders in
single- and multi-ridge low-index waveguides within a two-layer heterogeneously
integrated electro-optically active photonic platform. The transverse electric
(TE) polarized quasi-BIC guided mode with low, <1.4 dB/cm loss enables a
Mach-Zehnder electro-optic amplitude modulator comprising a single straight
Si3N4 ridge waveguide integrated with a continuous LiNbO3 slab layer. The
abrupt optical transitions at the edges of the slab function as compact and
efficient directional couplers eliminating the need for additional components.
The modulator exhibits a low insertion loss of 2.3 dB and a high extinction
ratio of 25 dB. The developed general theoretical model may enable innovative
BIC-based approaches for important PIC functions, such as agile spectral
filtering and switching, and may suggest new photonic architectures for quantum
and neural network applications based on controlled interactions between
multiple guided and delocalized modes
Agile chip-scale electro-optic frequency comb spectrometer with millivolt drive voltages
Here, we present an on-chip spectrometer that leverages an integrated
thin-film lithium niobate modulator to produce a frequency-agile electro-optic
frequency comb for interrogating chip-scale temperature and acceleration
sensors. The low half-wave voltage, , of the modulators and the
chirped comb process allows for ultralow radiofrequency drive voltages, which
are as much as seven orders of magnitude less than the lowest found in the
literature and are generated using a chip-scale, microcontroller-driven direct
digital synthesizer. The on-chip comb spectrometer is able to simultaneously
interrogate both the on-chip temperature sensor and an off-chip,
microfabricated optomechanical accelerometer with cutting-edge sensitivities of
and , respectively.
Notable strengths of this platform include the frequency agility of the optical
frequency combs, ultralow radiofrequency power requirements and compatibility
with a broad range of existing photonic integrated circuit technologies.Comment: 11 pages, 5 figure
An Efficient Large-Area Grating Coupler for Surface Plasmon Polaritons
We report the design, fabrication and characterization of a periodic grating
of shallow rectangular grooves in a metallic film with the goal of maximizing
the coupling efficiency of an extended plane wave (PW) of visible or
near-infrared light into a single surface plasmon polariton (SPP) mode on a
flat metal surface. A PW-to-SPP power conversion factor > 45 % is demonstrated
at a wavelength of 780 nm, which exceeds by an order of magnitude the
experimental performance of SPP grating couplers reported to date at any
wavelength. Conversion efficiency is maximized by matching the dissipative SPP
losses along the grating surface to the local coupling strength. This critical
coupling condition is experimentally achieved by tailoring the groove depth and
width using a focused ion beam.Comment: The final publication is available at http://www.springerlink.com.
http://dx.doi.org/10.1007/s11468-011-9303-