Model of 1D Photonic Crystal Silicon Waveguides by Varying the

Lattice Constant in Their Geometry Stucture via FDTD Method, in

the Field of Communication Photonics for Telco Purpose

Jamilah Husna

, Azmi Rizki Lubis

, Yusniati

, Ahmad Rifqi Md. Zain

and Mohd Ambri Mohamed

Faculty of Engineering, Universitas Islam Sumatera Utara, Medan, Indonesia

Institute of Microengineering and Nanoelectronics (IMEN), Level 4, Research Complex, Universiti Kebangsaan Malaysia,

Bangi, Selangor, Malaysia

Keywords: 1D Photonic Crystal, Waveguide, (FDTD), Wavelength Divisionmultiplexing (WDM), Siliconon Insulator

(SOI).

Abstract: The theoretical investigation of tuning a geometry structure of one dimensional (1D) photonic crystal

waveguides based on silicon on insulator (SOI) which has been conducted in UKM lab using Crystalwave

software (FDTD method) is the object of the research. The lattice distance has been varied from 110 nm up

to 165 nm, meanwhile the hole diameter iskept constant at 70 nm. The results show that the main physical

effects of the structure of numerical model could be applied towards the total Q factor and the transmission

performances and the ultrahigh Q factors reached to 3840 and the transmission obtained up to 65%.

1 INTRODUCTION

Photonics have existed as a new research ﬁeld for

more than ten years. It was founded in the late 1960s,

with the purpose of using light to perform functions

that traditionally fall into the domain of electronics.

Since few years ago, one of the major topics of

interest in photonic research is the study and

development of micro- and nano-structures for fast

signal processing in the telecom window. In addition,

due to their unique ability for manipulating photon

transmission, we assumed that the photonic crystal

(PhCs) will play a significant role in future photonic

and optical applications.

The ﬁrst successful inventions of photonics such

as laser diode and optical ﬁbers for long-haul data

transmission gave rise to the telecommunication

revolution in the end of the 20 century, which, in

return, became a strong driving force for further

photonic research. With the exception of the past

decade, photonics focused mainly at telecom

applications. Combining or replacing the electronic

circuits by integrated nanophotonic devices should

lead to a dramatic increase in the capacity of

transmitted data (ultra-high band- width with

Wavelength Division Multiplexing) and considerable

reduction of the power consumption. Wavelength

division multiplexing (WDM) is a technology used

for multiplexing signals in optical fibre. The main

advantage of the WDM technique in

telecommunication is that it allows the capacity of the

network to be increased without the need to change

the backbone of the fibr network.

This is made possible through implementing

WDM and deploying optical amplifier throughout the

optical network. The WDM optical spectrum is

divided into several distinct wavelengths that do not

overlap, and each wavelength corresponds to a single

communication channel, thus providing several

WDM channels in the same fiber and greatly utilising

the fibers huge bandwidth. With such large

bandwidth potential, research on WDM devices has

increased with the aim of employing WDM-based

optical backbones for the Internet. The conventional

WDM systems were dual-channel 1.31/1.55 μm

systems including both the minimum dispersion

window and minimum attenuation window.

The WDM consists mainly of two types: Coarse

WDM (CWDM) and Dense WDM (DWDM). In

communication systems, WDM devices show the

ability to improve coherence without losing the

quality of transmission, tightly compact (micrometre

scale) and practical to fabricate on integrated optical

circuits. This is where photonic crystals have much

Husna, J., Rizki Lubis, A., Yusniati, ., Rifqi Md. Zain, A. and Ambri Mohamed, M.

Model of 1d Photonic Crystal Silicon Waveguides by Varying the Lattice Constant in Their Geometry Stucture via Fdtd Method, in the Field of Communication Photonics for Telco Purpose.

DOI: 10.5220/0008882200460051

In Proceedings of the 7th International Conference on Multidisciplinary Research (ICMR 2018) - , pages 46-51

ISBN: 978-989-758-437-4

potential, as PhC-based WDM for different

wavelength selective-filterin techniques have been

recently realised. Such devices include filter adjacent

to waveguides, using coupling techniques

(Zimmermann et al., 2004) or cavities (Pustai et al.,

2002) for the purpose of achieving PhC-based

wavelength multiplexing and demultiplexing.

Photonic crystals (PCs) are artificial structures

with a periodic dielectric constant in one, two or three

dimensions. They are characterized by photonic band

structures owing to the multiple Bragg scatterings

(Qin et al., 2003). In 1987 the concept of photonic

crystals (PCs) was first proposed by Yablonovitch

and John(Yablonovitch, 1987). They found that by

using periodic arrangement of dielectric mate-rials

which possible for us to control the propagation of the

electro-magnetic waves. If this periodic arrangement

is on the order of the wavelength of light, then for

some range of wavelengtht, it is called Photonic Band

Gap, where in this gap light cannot reach the crystal.

The propagation of light waves is strongly influenced

by the band structures and forbidden in the photonic

band gaps (PBG) (Shiveshwari and Mahto, 2006).

The propagation of a light wave can be manipulated

by PBG. Therefore, many optics effects may be

realized in PCs. By introducing defects into the PBG

structure, for example, resonance modes or defective

modes (Noda et al., 2000).

For the last few years, Photonic crystals (PCs)

structures have attracted, and have been the research

subjects of growing interests. It is well-known, that

the structure is designed to control the propagation of

electromagnetic waves in the same way as the

periodic potential in semiconductor crystals

(Soukoulis, 2006). The dimensional photonic gems

have been referred to for quite a few years as Bragg

reflects. Impedance of the Bragg disseminating is

considered as a reason for the Bragg hole or band

hole. The periodicity makes the band holes rely upon

a few parameters, as the dielectric differentiate

between the utilized materials, and the filling

component of the rudimentary cell. Valuable property

is owned by one gem photonic structure (1D-PC),

which is utilized as an unfortunate optical waveguide,

reflective mirror, optical switch, optical barrier, and

dielectric optical channel.

2 MATERIAL AND METHOD

Silicon on insulator (SOI) was chosen as the main

material to use in this work. A few materials have

been connected with a specific end goal to acquire

one photonic precious stones (1D, for

example,Si/SiO2,SiO2/TiO2,Na3AlF6/ZnSe,Na3Al

F6/Ge(Srivastava and Ojha, 2007). Among the many

existing material frameworks, silicon on cover (SOI)

is considered as the best possibility to create

coordinated nano-photonic gadgets as it permits the

solid reconciliation of optical and electronic gadgets,

that is by staying away from the utilization of half and

half bundling procedures. Silicon PhC structure-

based devices have been used in a wide range of

applications, including light flow control applications

such as waveguides, photonic band gap structures,

and resonators. In this case, all the requirements can

be satisfied by varying one-dimensional photonic

crystal (PhC) structures with narrow\ waveguides in

high refractive index contrast materials, such as

silicon-on insulator (SOI) as reported byLee. (2014).

We then created the defect on one-dimensional

(1D) Photonic crystals waveguide geometry

structure. Furthermore, the brief report regarding the

problem of determining the quality (Q) factor of

localized cavity modes are presented. Each cavity is

formed by introducing a central region with no holes

and tapering the lattice constant and hole size near the

cavity region (McCutcheon and Loncar, 2008). The

observed influence of the presented defect on the

geometry 1DPhotonic crystal cavity structure

waveguide has been conducted. The simulation

results such as the overall characteristics are

investigated.There are the resonance peak

wavelengths, transmission and the Q-performances

affected by the tuning geometry structure in lattice

segment particularly. For further step, we hope the

results from this model devices are considered as

potential building blocks in Silicon-On-Insulator

(SOI) planar photonic integrated circuits operating, in

particular at optical wavelengths for advanced

telecom applications.

As reported that by tuning the

geometry/dimension of the 1-D PhC structures, the

transmission properties can be affected, and by

replacing the homogeneous cavity construction with

double cavities of the normal 1-D PhC, a multi-

wavelengh-transmission optical filter can be realized.

In fact those resonances can be controlled through the

variation of parameters, such as hole dimension,

lattice and cavity lengths (Md Zain et al., 2010).

Some years ago, Srinivasan et al report that if the

cavity has the proper size to support a mode in the

band gap, then light cannot escape, resulting in the

pinning of the mode to the defect (Quan et al., 2010),

and this gave the effect that a resonant cavity is

formed. This structure allows nearly an independent

tuning of each resonant frequency by tuning the

parameters (e.g. width, lattice constant, cavity length)

Model of 1d Photonic Crystal Silicon Waveguides by Varying the Lattice Constant in Their Geometry Stucture via Fdtd Method, in the Field

of Communication Photonics for Telco Purpose

each beam and has natural channels for coupling

through each beam to an access waveguide at each

wavelength (Lourtioz et al., 2008), and this pattern

model inspired our model design in our work.

Figure 1: Schematic Design of Hole Pattern of One

Dimensional (1D) Photonic Crystal Cavities Waveguide.

Figure 2: Sketch of 3D FDTD simulation transmission

spectra of the compound photonic crystal cavity waveguide

with multiple resonance results (a), and (b) calculation for

Q factor by Lorentzian ﬁtting.

The three-dimensional (3D) FDTD method has

been used to simulate the designs. We employed the

Crystalwave (Omnisim) software, the available

software in lab, and to overcome some problem

memory leading to large 3D simulations for which we

employed the supercomputer infrastructure at

National University of Malaysia (UKM). Numerical

simulations play an important role for the design and

modelling of guided wave optoelectronic devices. 1D

periodic computational techniques and modelling are

useful and sufficiently well-established

(Joannopoulos et al., 1995). The FDTD method is a

quite general method for the simulation of

electromagnetic devices for all range of frequencies

from the microwave to the optical regime. The power

of the method lies in its simple formulation in which

no restrictive assumptions are made in order to

preserve its applicability to a wide range of problems,

considering a 3D space with no electric or magnetic

current sources, but with materials that present

electric and magnetic conductivity. The last decade

has witnessed dramatic progress and interest in

micro- and nanofabrication techniques of complex

photonic devices (Yee, 1966). FDTD method is

famous due to its large flexibility and extendibility.

Many types of calculations can be performed through

fairly robust algorithms. The design process consists

of engineering three elements: (a) the taper, (b) the

photonic crystal mirror (Phc), and (c) the cavity

length and (d). Middle hole section. The progress in

micro and nanofabrication techniques of complex

photonic devices have been observed. An accurate

quantitative theoretical modelling of these devices

has to be based on advanced computational

techniques that can solve the relevant linear,

nonlinear or coupled partial differential equations

since over last decade (Obayya, 2011).

The proposed waveguide PhC structure that we

presented in this work, consists of a 1D hole array in

a silicon-on-insulator (SOI) photonic wire

waveguide, and the geometry of the proposed

waveguide is as illustrated in Fig. 1. The references

are (Lan and begs) based on the tight requirement of

a WDM system operating to the ITU standard. A

coupled cavity structure was investigated as an ideal

candidate to form a band-pass optical filter based on

1-D PhCs. Based on this, we created the design of

geometry/dimensional structure of one dimensional

(1D) photonic crystal waveguide by placing the three

cavity in that structure, with the purpose to obtain the

multiple peak resonances, good transmissions and

higher Q factor. Numerical simulations play an

important role for the design and modeling of guided

wave optoelectronic devices. 1D periodic

computational techniques and modeling are useful

and sufficiently well-established (Anon, 1995). The

design process consists of engineering three

elements: (a) the taper, (b) the photonic crystal mirror

(Phc), and (c) the cavity length and (d). Middle hole

section. The details of the description of the basic

design can be seen in Fig. 1, where the taper is located

on the external cavity side of the mirror and the row

of seven holes with diameters of 110, 110, 135, 135,

165, 135, 110 nm respectively, and is separated by

increasing distances. Here, between the external

cavities there are several additional tapers as shown

in Fig. 1, the name is the middle hole section taper,

and we keep the those hole diameters at 70 nm. In this

(b)

ICMR 2018 - International Conference on Multidisciplinary Research

work, we focus on varying the lattice constant by

varying the lattice distance from 320nm -

355nm.Here, the structure is restructured as follows:

silica (n=1.445) with a thickness of 1100 nm; silicon

(n=3.48) with a thickness of 600 nm; and the last layer

is air (n=1) with a thickness of 1000 nm. For the

adjusting refracting index parameters value for SOI

device structures we keep them constant.

The resonance wavelength, the Q-factor and the

transmission/reflectance performance have been

computed using the Finite Difference Time Domain

(FDTD) approach. The Q-factor results was obtained

from Lorentzian ﬁtting and the description of this

calculation as illustrated in Fig.2.

3 RESULTS AND DISCUSSION

In this study, we try to explore the possibility of

employing more cavities waveguide design

supporting two or more resonances (especially with

both mode design the telecom window). In the other

case, by design, a longer or a shorter of lattice wide,

and/or coupled photonic cavities geometry structure

waveguide and this increases the Q factor and

transmission values. The change in Q depends

strongly on the waveguide properties such as the

width band gap. The other fact shows that the Q factor

value was also affected by other parameters such as

defect and etch. First, we investigated the influence

of the presented defect geometry structure by varying

the lattice constant size and placing three cavities

between the mirror/taper. We define that by applying

325 nm lattice size in geometry waveguide design

which we achieved from the highest Q- factor. The Q-

factor was calculated using λp/Δλ, where Δλ is the

band width of the resonance peak. The spectrum

shows a resonance for the wavelength 1525 nm with

a Q-factor of approximately 3840.

Figure 3: The graph of Q-factor toward lattice constant.

Figure 4: The graph of Multi Resonance wavelength peaks

by varying lattice distance.

We assumed that the higher Q-factors achieved

from simulation in this work probably was caused by

the small of the lattice size. On the other hand, the

simulation results show that changing the geometry

parameters of waveguide has the effect on the

enlargement of the band gap wavelength. This means

that the lattice constant is an important factor in the

performance of the band gap width beside other

parameter. Based on simulation analyzed, we found

that the band gap width becoming larger with the

increase of the lattice size for all the five cases. As

illustrated in fig.3. it shows that the structure exhibits

various band gaps (or stop band) where the photonic

states are not forbidden with the existence of three

resonance peaks for each case/design. The multiple

resonances peak for overall designs were found in

range wavelength area from 1430 up to1690 nm. As

can be seen in Fig. 4. it shows the linear resonance

wavelength peaks resulted of a whole device with

identical geometry parameters, for all case designs. In

addition, Obayya reports that the shift of the

resonance towards longer wavelength can be

explained by a strong nonlinear effect due to the

effect of the magnetic field applied to the structure.

The changing of lattice size modified in this study

has significant effect on the optical response

especially to control the transmittance of the device.

Furthermore, the transmission spectra for a whole

design has been computed and plotted with different

wavelength cantered value for each design. As can be

seen from the graft (Fig.5.) that the transmission

results were varied with a little fluctuation, and

obtained values via transmission spectrum method.

The transmissions obtained were above 30 %, with

the maximum value achieved at 75% when the lattice

size was set at 350 nm. From our perspective, we

310 320 330 340 350 360

1400

1600

1800

2000

2200

2400

2600

2800

3000

3200

3400

3600

3800

4000

4200

Q-Factor

L a ttic e s ize (n m )

310 320 330 340 350 360 37

1420

1440

1460

1480

1500

1520

1540

1560

1580

1600

1620

1640

1660

1680

1700

Resonance Wavelength (nm)

Lattice size (nm )

Model of 1d Photonic Crystal Silicon Waveguides by Varying the Lattice Constant in Their Geometry Stucture via Fdtd Method, in the Field

of Communication Photonics for Telco Purpose

assume that fluctuation of the transmission values are

due to the numerical errors of the calculations. As

reported in our previous paper that for further

increase, the transmission coefficient peak can be

expected by optimizing the size of the hole radius of

middle hole sections, and with the realization of taper

sections inside the resonant cavity (Husna et al.,

2015). As the Q factor gets higher then the

transmission (T) result will be smaller, and the trend

of the transmission results obtained from our work are

consistent with those previous reports. As overall, the

presented results as illustrated in our calculated

curves (Q- factor, transmission and resonance

wavelength) coincide well and match with the

simulation results in Fig. 2. On the other hand, the

normalized transmission of the resonance varies at

which we believe that the Q-factor and optical

transmission is optimum for a certain cavity condition

as reported by Zain et al., (2015). The other group

researchers supporting our results mention that the

structures may have application to WDM devices in

the range IR to THz, depending on the geometry

(Faneca et al., 2018).

Figure 5: The graft of the normalized transmission spectrum

of 1D photonic crystal cavities waveguide.

4 CONCLUSION

For the conclusion, we successfully investigate the

confine light process in a 1D PhC a silicon waveguide

structure. We have confirmed that it is possible to

modify the geometry of waveguide structure by

varying the number of cavity, lattice, radius and the

number of hole in the periodicity. The wavelength

range in this area (1300 -1550 nm) window has

become very vital in view of the availability of

wavelength division multiplexing (WDM)

transmission system and optical amplifiers (erbium-

doped fiber amplifiers). We found that the model of

1D photonic crystal silicon waveguide designed in

our research is in accordance with properties expected

for different lattice design condition based on

simulation results and it is acceptable to be utilized

for Telco purpose. We optimized that these

wavelengths could be used in a wavelength division

Multiplexing (WDM) system.

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Model of 1d Photonic Crystal Silicon Waveguides by Varying the Lattice Constant in Their Geometry Stucture via Fdtd Method, in the Field

of Communication Photonics for Telco Purpose