79 research outputs found
Monolithic whispering-gallery mode resonators with vertically coupled integrated bus waveguides
We report on the realization and optical characterization of a
CMOS-compatible silicon-based microresonator/waveguide coupled system, fully
integrated on a silicon chip. The device uses a vertical coupling scheme
between the resonator and a buried strip waveguide. We demonstrate that its
high optical quality follows from the accurate planarization of the waveguide
topography. More importantly, we demonstrate a wafer-scale mass fabrication of
freestanding planar resonators suspended in air and coupled to the integrated
bus waveguides. A nanometer control of the coupling distances allows for a
precise and selective excitation of different mode families of the resonator.
This opens the door for the realization of stable all-integrated complex
resonator systems for optomechanical and metrological applications, with the
potential to substitute the nowadays intensive use of complicated fiber-taper
coupling schemes.Comment: 3 pages, 3 figure
Role of edge inclination in optical microdisk resonator for label-free sensing
In this paper we report on the measurement and modelling of enhanced optical
refractometric sensors based on whispering-gallery-modes. The devices under
test are optical microresonators made of silicon nitride on silicon oxide. In
our approach, these microresonators are vertically coupled to a buried
waveguide with the aim of creating integrated and cost-effective devices. The
optimization analysis is a delicate balance of resonance quality factor and
evanescent field overlap with the sorrounding environment to analyze. By
numerical simulations we show that the microdisk thickness is critical to yield
high figure of merit for the sensor, while edge inclination is less important.
We also show that figures of merit as high as 1600/RIU are feasible.Comment: 10 page
Compact Quantum Random Number Generator with Silicon Nanocrystals Light Emitting Device Coupled to a Silicon Photomultiplier
A small-sized photonic quantum random number generator, easy to be implemented in small electronic devices for secure data encryption and other applications, is highly demanding nowadays. Here, we propose a compact configuration with Silicon nanocrystals large area light emitting device (LED) coupled to a Silicon photomultiplier to generate random numbers. The random number generation methodology is based on the photon arrival time and is robust against the non-idealities of the detector and the source of quantum entropy. The raw data show high quality of randomness and pass all the statistical tests in national institute of standards and technology tests (NIST) suite without a post-processing algorithm. The highest bit rate is 0.5 Mbps with the efficiency of 4 bits per detected photon
Silicon Photonics Chip for Inter-modal Four Wave Mixing on a Broad Wavelength Range
We design, fabricate and test an integrated silicon photonics chip for inter-modal four wave mixing, whose phase-matching relays on the modal dispersions of different waveguide modes. This phase-matching technique allows for tunable and broadband wavelength conversion and generation. We demonstrate that idler and signal photons can be generated with 800 nm spectral distance in between. We measure several inter-modal combinations, with up to the third order mode involvement. We demonstrate a maximum conversion efficiency of -12.4 dB from 1468.5 nm to 1641.1 nm with a bandwidth of 11 nm. We also prove the high and broadband tunability of the generated signal by scanning the pump wavelength when the signal wavelength is fixed. All these features make the inter-modal four wave mixing a viable solution for all optical processing in the near as well as in the mid infrared and for quantum applications
A fully integrated high-Q Whispering-Gallery Wedge Resonator
Microresonator devices which posses ultra-high quality factors are essential
for fundamental investigations and applications. Microsphere and microtoroid
resonators support remarkably high Q's at optical frequencies, while planarity
constrains preclude their integration into functional lightwave circuits.
Conventional semiconductor processing can also be used to realize
ultra-high-Q's with planar wedge-resonators. Still, their full integration with
side-coupled dielectric waveguides remains an issue. Here we show the full
monolithic integration of a wedge-resonator/waveguide vertically-coupled system
on a silicon chip. In this approach the cavity and the waveguide lay in
different planes. This permits to realize the shallow-angle wedge while the
waveguide remains intact, allowing therefore to engineer a coupling of
arbitrary strength between these two. The precise size-control and the
robustness against post-processing operation due to its monolithic integration
makes this system a prominent platform for industrial-scale integration of
ultra-high-Q devices into planar lightwave chips.Comment: 6 pages, 4 figure
Whispering-gallery modes and light emission from a Si-nanocrystal-based single microdisk resonator
We report on visible light emission from Si-nanocrystal based optically
active microdisk resonators. The room temperature photoluminescence (PL) from
single microdisks shows the characteristic modal structure of
whispering-gallery modes. The emission is both TE and TM-polarized in 300 nm
thick microdisks, while thinner ones (135 nm) support only TE-like modes.
Thinner disks have the advantage to filter out higher order radial mode
families, allowing for measuring only the most intense first order modal
structure. We reveal subnanometer linewidths and corresponding quality factors
as high as 2800, limited by the spectral resolution of the experimental setup.
Moreover,we observe a modification of mode linewidth by a factor 13 as a
function of pump power. The origin of this effect is attributed to an excited
carrier absorption loss mechanism.Comment: 5 pages, 5 figure
Inter-mode reactive coupling induced by waveguide-resonator interaction
We report on a joint theoretical and experimental study of an integrated photonic device consisting of a single mode waveguide vertically coupled to a disk-shaped microresonator. Starting from the general theory of open systems, we show how the presence of a neighboring waveguide induces reactive inter-mode coupling in the resonator, analogous to an off-diagonal Lamb shift from atomic physics. Observable consequences of this coupling manifest as peculiar Fano lineshapes in the waveguide transmission spectra. The theoretical predictions are validated by full vectorial 3D finite element numerical simulations and are confirmed by the experiments
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