Modelling Of CMOS Based Interleaved PN Junction Optical Phase Shifters
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Date
2019-01-01
Authors
Javid Shaikh, Abdurrahman
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
The performance of an optical interconnect depends on the underlying optical
modulator design. Performance of these modulators is largely influenced by the
embedded optical phase shifters. Among several topologies, depletion-mode
interleaved junction phase shifters are most promising because of the high speed
associated with depletion mode of operation and high modulation efficiency
associated with interleaved junction structure. Due to structural complexity of
interleaved topology, the phase shifter performance depends on several design
parameters. Also, intricate trade-offs exist among various performance metrics with
respect to these design variables. For viable modulator design, optimization is
necessary which requires performance predictive models. In the literature, only
preliminary numerical research has been pursued to understand the behaviour of such
a promising topology, that too, with many simplifying unrealistic assumptions.
Interleaved junction phase shifters, however, require rigorous three-dimensional (3D)
modelling for true description of the modulator performance. Such 3D mathematical
predictive models are absent in the literature. In this thesis three dimensional
optoelectronic simulations, incorporating physics-based models and adequate
correction models, have been performed to obtain rigorous numerical results. The
overall workflow is divided in three stages. Industry standard tools from Lumerical
Inc. based on Finite-Difference-Frequency-Domain (Lumerical MODE Solutions),
Finite-Element-Modelling (Lumerical DEVICE TCAD), and Finite-Difference-Time-Domain (Lumerical FDTD Solutions) have been used for waveguide (stage 1),
device (stage 2) and phase shifter (stage 3) performance modelling respectively.
Nonlinear predictive models are then obtained by pursuing careful, stage-wise curve
fitting procedures using MATLAB 2015b. For the first time, comprehensive
mathematical guidelines for the passive design of submicron rib waveguides have
been proposed along with mathematical predictive models for modulation efficiency,
capacitance per unit length, and bandwidth of the optical phase shifters. The
accuracy of the models have been compared against the foundry fabricated designs.
An estimation error of about 7% or below was noted for all the proposed models.
Such models would enable application specific optimization of submicron silicon
interleaved PN-junction optical phase shifters.