29 research outputs found
Modeling quasi-dark states with Temporal Coupled-Mode Theory
Coupled resonators are commonly used to achieve tailored spectral responses
and allow novel functionalities in a broad range of applications, from optical
modulation and filtering in integrated photonic circuits to the study of
nonlinear dynamics in arrays of resonators. The Temporal Coupled-Mode Theory
(TCMT) provides a simple and general tool that is widely used to model these
devices and has proved to yield very good results in many different systems of
low-loss, weakly coupled resonators. Relying on TCMT to model coupled
resonators might however be misleading in some circumstances due to the
lumped-element nature of the model. In this article, we report an important
limitation of TCMT related to the prediction of dark states. Studying a coupled
system composed of three microring resonators, we demonstrate that TCMT
predicts the existence of a dark state that is in disagreement with
experimental observations and with the more general results obtained with the
Transfer Matrix Method (TMM) and the Finite-Difference Time-Domain (FDTD)
simulations. We identify the limitation in the TCMT model to be related to the
mechanism of excitation/decay of the supermodes and we propose a correction
that effectively reconciles the model with expected results. A comparison with
TMM and FDTD allows to verify both steady-state and transient solutions of the
modified-TCMT model. The proposed correction is derived from general
considerations, energy conservation and the non-resonant power circulating in
the system, therefore it provides good insight on how the TCMT model should be
modified to eventually account for the same limitation in a different
coupled-resonator design. Moreover, our discussion based on coupled microring
resonators can be useful for other electromagnetic resonant systems due to the
generality and far-reach of the TCMT formalism.Comment: 7 pages, 4 figure
Spectral Engineering with Coupled Microcavities: Active Control of Resonant Mode-Splitting
Optical mode-splitting is an efficient tool to shape and fine-tune the
spectral response of resonant nanophotonic devices. The active control of
mode-splitting, however, is either small or accompanied by undesired resonance
shifts, often much larger than the resonance-splitting. We report a control
mechanism that enables reconfigurable and widely tunable mode-splitting while
efficiently mitigating undesired resonance shifts. This is achieved by actively
controlling the excitation of counter-traveling modes in coupled resonators.
The transition from a large splitting (80 GHz) to a single-notch resonance is
demonstrated using low power microheaters (35 mW). We show that the spurious
resonance-shift in our device is only limited by thermal crosstalk and
resonance-shift-free splitting control may be achieved.Comment: 4 pages, 3 figure
Loss compensation in microring-based Si photonics devices via Er3+doped claddings
FAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTĂFICO E TECNOLĂGICOWe propose and demonstrate a method to compensate insertion losses in Si photonics devices based on ring resonators fabricated in SOI foundries, with no additional chip area used. It consists in the employment of Er:Al2O3 as the upper cladding layer on standard Si/SiO2 rings, requiring only one simple post-processing step. The method is modeled in detail, and simulation results for single-ring configurations and photonic molecules are discussed, where the potential for loss reduction is predicted for different design choices based on the quality factor. We experimentally verify the viability of the method, obtaining an output power increase of 1 dB when a single-ring resonator is pumped. This value is increased when the method is applied to devices based on photonic molecules, where a value of 2.6 dB has been measured. This is equivalent to a loss reduction potential higher than 3 dB for a photonic molecule designed to achieve a quality factor of 50000.104113FAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTĂFICO E TECNOLĂGICOFAPESP - FUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTĂFICO E TECNOLĂGICO08/57857-22014/04748-2574017/2008-
Reconfigurable silicon thermo-optical ring resonator switch based on Vernier effect control
A proof-of-concept for a new and entirely CMOS compatible
thermo-optic reconfigurable switch based on a coupled ring resonator structure is experimentally demonstrated in this paper. Preliminary results show that a single optical device is capable of combining several functionalities, such as tunable filtering, non-blocking switching and
reconfigurability, in a single device with compact footprint (~50ÎŒm x 30ÎŒm)