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Applied Physics B (2019) 125:12
https://doi.org/10.1007/s00340-018-7123-6
On‑chip hybrid demultiplexer formode andcoarse wavelength
division multiplexing
YuyangZhuang
1,2
· HemingChen
3
· KeJi
1,2
· YuchenHu
1,2
Received: 15 July 2018 / Accepted: 15 December 2018
© Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract
We propose a hybrid demultiplexer for mode and coarse wavelength division multiplexing on silicon-on-insulator (SOI)
nanowires and photonic crystal (PhC) slab. First, a V-shape waveguide–cavity–waveguide filter based on PhC slab is pre-
sented. Coupling of resonant modes is introduced to the filter to suppress the crosstalk caused by connection with nanow-
ires. Then, we cascade and optimize the filter to compose a coarse wavelength division demultiplexer. After that, a hybrid
demultiplexer is constructed by combining the coarse wavelength division demultiplexer on PhC slab and mode division
demultiplexer on SOI nanowires. The parameters of the hybrid demultiplexer are calculated using three-dimensional finite-
difference time-domain (3D-FDTD) method. The numerical results show that the fundamental transverse electric (
TE
0
)
modes and the first-order TE (
TE
1
) modes of 1530 nm and 1550 nm can be demultiplexed. The insertion loss is smaller than
2.0 dB, and the channel crosstalk is less than − 25 dB. The hybrid demultiplexer can be applied in a system that using mode
and coarse wavelength division multiplexing simultaneously.
1 Introduction
Current optical communication works mostly in single-mode
system. The wavelength division multiplexing (WDM) has
been a key technology utilized to enhance transmission
capacity. With the transmission capacity of optical fiber
approaching to Shannon limit, space division multiplexing
(SDM) [1, 2] has received increasing attention, trying to
improve the capacity further. The development of SDM is
mainly embodied in the application of multicore fiber [3]
and few-mode fiber [4]. Similarly, the on-chip hybrid multi-
plexing system combining WDM and mode division multi-
plexing (MDM) technologies has also become the research
focus.
There are many types of on-chip WDM devices, such
as those based on arrayed waveguide gratings (AWG) [5],
micro-ring resonators (MRR) [6], and photonic crystal res-
onators (PCR) [7, 8], etc. Although AWG has been com-
mercialized, the footprint of it is much larger than that of
the latter two, thus, MRR and PCR are more suitable for
ultrasmall photonic integrated devices in the future. Com-
pared with MRR, PCR has a larger transmission bandwidth
given its special transmission mechanism. Hence, PCR is
more suitable for CWDM system, while MRR is known to
be limited by its free spectral range (FSR). For example, a
micro-ring with a radius of 6.735
μm
only has an FSR of
16 nm [6]. Similarly, there are also several on-chip MDM
devices brought up in recent years, including those based
on adiabatic mode evolution (AME) [9], multi-mode inter-
ference (MMI) [10], y-junctions [11, 12], and asymmetric
directional couplers (ADC) [13, 14]. Among them, the trans-
mission capacity of MMI is limited. In addition, the designs
of AME and y-junctions have always been complex. Com-
pared with them, ADC is a better choice for the design of
on-chip MDM devices, because it has a simpler structure.
Moreover, it is much easier to be extended.
Hybrid demultiplexers could be constructed by cascading
WDM and MDM devices. Here, we take ADC-type MDM,
for example, on account of the superiority of ADC. Mulug-
eta [15] proposed an ADC–MMI type MDM–WDM device,
which can demultiplex the fundamental and first-order
modes of 1310 nm and 1550 nm. Although the size of the
* Heming Chen
chhm@njupt.edu.cn
1
Department ofElectronic andOptical Engineering,
Nanjing University ofPosts andTelecommunications,
Nanjing210023, China
2
Department ofMicroelectronics, Nanjing University ofPosts
andTelecommunications, Nanjing210023, China
3
Bell Honors School, Nanjing University ofPosts
andTelecommunications, Nanjing210023, China
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