Large-signal SPICE model for depletion-type
silicon ring modulators
MINKYU KIM,
1
MYUNGJIN SHIN,
1,2
MIN-HYEONG KIM,
1,3
BYUNG-MIN YU,
1
YOUNGHYUN KIM,
1,4
YOOJIN BAN,
1,4
STEFAN LISCHKE,
5
CHRISTIAN MAI,
5
LARS ZIMMERMANN,
5
AND WOO-YOUNG CHOI
1,
*
1
Department of Electrical and Electronic Engineering, Yonsei University, 03722 Seoul, South Korea
2
Now at University of Michigan, Ann Arbor, 48109 Michigan, USA
3
Now at Samsung Electronics, Hwasung, 18448 Gyeonggi-do, South Korea
4
Now at IMEC, Kapeldreef 75, 3001 Leuven, Belgium
5
IHP, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
*Corresponding author: wchoi@yonsei.ac.kr
Received 15 April 2019; revised 26 June 2019; accepted 26 June 2019; posted 28 June 2019 (Doc. ID 364895); published 7 August 2019
We present an accurate, easy-to-use large-signal SPICE circuit model for depletion-type silicon ring modulators
(Si RMs). Our model includes both the electrical and optical characteristics of the Si RM and consists of circuit
elements whose values change depending on modulation voltages. The accuracy of our model is confirmed by com-
paring the SPICE simulation results of 25 Gb/s non-return-to-zero (NRZ) modulation with the measurement. The
model is used for performance optimization of monolithically integrated Si photonic NRZ and pulse-amplitude-
modulation 4 transmitters in the standard SPICE circuit design environment.
© 2019 Chinese Laser Press
https://doi.org/10.1364/PRJ.7.000948
1. INTRODUCTION
Depletion-type silicon ring modulators (Si RMs) attract a great
amount of research interests since they can provide advantages
for optical interconnect (IC) applications such as large modu-
lation bandwidth and small power consumption [1–4].
Furthermore, Si RMs are much smaller than the widely used
Si Mach–Zehnder modulators (MZMs) and, consequently, al-
low much easier monolithic integration with electronics. Such
electronic–photonic integration is necessary for interconnec-
tion solutions for future high-performance electronic systems
in which photonic solutions must be as closely located to elec-
tronics as possible for size and power consumption reduction
[5]. To realize Si electronic–photonic ICs containing Si RMs, a
Si RM equivalent circuit model that is accurate, easy-to-use,
and compatib le with the standard IC design environment is
highly desirable. In addition, extracting numerical values for
model parameters should be simple and straight-forward.
Although there have been several published reports on
depletion-type Si RM models, none satisfies the above require-
ments. In Ref. [6], a precise analytical model for a Si RM was
reported, but it requires more than 10 parameters and is not
very compatible with the standard Si IC design environmen t.
We reported a Verilog-A implementation of a coupled-mode
description of the Si RM [7], which can be easily executed
in the SPICE simulation environment. It, however, requires
a substantial amount of computation time because Verilog-A
is not optimized for numerically solving differential equations
and, consequently, the simulation must use a very fine time
resolution to accurately describe Si RM dynamics.
In this paper, we present a large-signal equivalent circuit
model based on the linear equivalent circuit of the Si RM
[8], which contains only a few independent model parameters
that can be easily extracted from the simple RM transmission
measurement. Although model parameter values nonlinearly
depend on the Si RM bias voltage, we demonstrate that,
by using voltage-dependent circuit elements available within
SPICE, large-signal transient modulation characteristics can
be easily and accurately simulated at least 220 times faster than
the approach used in Ref. [7]. Such a reduction in computation
time should provide a great advantage for design optimization
of optical interconnection solutions for high-performance elec-
tronic systems that may contain numerous Si RMs as well as
various electronic circuit blocks. An initial portion of this work
was reported in Ref. [9]. In this paper, a more detailed descrip-
tion of our model is presented. In addition, we provide how our
model can be used for performance optimization of pulse-am-
plitude modulation 4 (PAM-4) transmitters containing Si RMs
and SiGe BiCMOS transistors.
This paper is organized in four chapters. In Chapter 2, after
a brief description of the Si RM device used for our investiga-
tion, we give the details of our model and explain how model
parameters are extracted from measurement results. The accu-
racy of the model also is verified with a 25 Gb/s non-return-to-
zero (NRZ) measurement. In Chapter 3, we demonstrate the
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Vol. 7, No. 9 / September 2019 / Photonics Research
Research Article
2327-9125/19/090948-07 Journal © 2019 Chinese Laser Press