1. Modelling of TiO2 based slot waveguides with
high optical confinement in 90o arc
Author
Sergey Degtyarev
Co-Author and Presenter
Muhammad Ali Butt
Senior Scientist
Samara State Aerospace University, Russia
ICECUBE CONFERENCE, 11-12 April 2016
Quetta, Pakistan

2. Straight channel waveguide
S-bend waveguide
Power splitter (Y-splitter)
Waveguide reflector
EO phase modulator
Mach-Zehnder Interferometer
EO-TE/TM converter
Anisotropic
directional coupler
Introduction
1
Basic integrated photonic components

3. Conventional waveguides
Waveguides are the structures that confines
the optical radiation by total internal reflection
Step -index waveguide
Graded-index waveguide
Techniques of fabrication
Step-index Graded-index
Liquid phase epitaxy Ion exchange
Molecular beam epitaxy Proton exchange
Pulsed laser deposition Metal diffusion
Sputtering Ion implantation
Laser writing(refractive index
modification)
a) Radiation mode
b ) Substrate mode
c) Guided mode
Light
behaviour
in optical
waveguide
2

4. Slot Waveguide
A slot-waveguide produces high E-field amplitude, optical power, and
optical intensity in low-index materials at levels that cannot be achieved with
conventional waveguides.
Schematic of slot waveguide. The propagation
of light is in “Y” direction
Electric field distribution at the
output of slot waveguide
3

5. Applications of slot waveguides
• Slot waveguide can be used to greatly increase the sensitivity of compact
optical sensing devices.
• It provides highly efficient interaction between fields and active materials
which lead to all- optical switching, optical amplification and optical
detection.
Ring resonator based gas sensor
J. Leuthold, C. Koos & W. Freude Nature
Photonics 4, 535 - 544 (2010)
Enhanced Evanescent confinement in
multiple-slot waveguides and its application
in biochemical sensing
IEEE Photonics Journal (2009)
4

6. Selection of waveguide material
• Titanium dioxide is a potential photonic material.
• It has high refractive index (2.4) which can enhance optical confinement
down to nanoscale dimensions and tight waveguide bends for dense on-chip
integration.
• It is transparent over a broad range of wavelength that comprises the visible
and near infrared.
• It is non linear photonic material. As compared to silica, its nonlinearity is 25
times higher.
5

7. Simulation parameters
• Simulations are conducted with Comsol
Multiphysics @ software
• Calculation method =Helmholtz equation
solving with the finite element
• Grid size= λ / 30 for TiO2 claddings and λ / 10
or air slot
• Refractive index n=2.433
• Wavelength λ = 1520 nm
• Slot width is 50 nm
• Waveguide height H = 400 nm
• Overall waveguide width = 450 nm
• Radius of Curvature range=400 to 1600 nm
Electric field distribution at the
output of slot waveguide
Slot waveguide with bend 6

8. TE and TM polarization
1520 nm at TM polarization 1520 nm at TE polarization
Electric field intensity pattern at the output of slot waveguide
7

9. Slot waveguide with 90o arc configuration
Schematic of symmetric Slot waveguide
with 90o bend
Electric field distribution at the output of 90o
bend symmetric slot waveguide with 1 µm
radius of curvature
Electric field distribution at the output of
Symmetric slot straight waveguide
8

10. Proposed configuration for better
confinement of light in slot waveguide
Slot displacement towards
inside of bend
Slot displacement towards
outside of bend
9

11. 10
Electric field distribution at the output of slot
waveguide
Symmetric slot straight waveguide 90o bend symmetric slot waveguide
with 1 µm radius of curvature,
Asymmetric slot waveguide with 1 µm
radius of curvature, slot displaced outside of
the bend
Asymmetric slot waveguide with 1µm
radius of curvature, slot displaced inside
of the bend

12. Study of relative power in the slot
Normalized relative power restrained in the slot for various
slot displacements and bend radius
11

13. Losses in the slot due to bends
Slot waveguide losses due to bends for different radius of
curvature at constant slot displacement
Losses= 10x log(Pout/Pin)
12

14. Conclusion
• The influence of the slot width and displacements on the TE modal
solution of the waveguides of several bend radii was studied with the
help of Comsol multiphysics software simulations.
• The high confinement of the EM field can be realized by embedding
the asymmetrical slot arrangement relative to the center of the
waveguide. This enhances the electric and power field densities in the
slot.
• Such high confinement permits the realization of new photonic devices
such as directional couplers, ring resonators, splitters and de-
multiplexers based on slot waveguides which require strong field
intensities to create nonlinear effects. This will encourage the
fabrication of compact integrated optical elements on chip.
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15. Thank you very much for your
attention!!!!

16. Modelling of TiO2 based slot waveguides with
high optical confinement in 90o arc
Muhammad Ali Butt
Senior Scientist
Science and Research Laboratory of Automated
systems of Science Researches,
Samara State Aerospace University, Russia
Email: m.a.butt@ssau.ru
ICECUBE CONFERENCE, 11-12 April 2016
Quetta, Pakistan