Modelling of TiO2 based slot waveguides with high optical confinement in 90o arc

AuthorSergey Degtyarev

Co-Author and PresenterMuhammad Ali Butt

Senior Scientist

Samara State Aerospace University, Russia

ICECUBE CONFERENCE, 11-12 April 2016Quetta, Pakistan

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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

IntroductionBasic integrated photonic components

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Conventional waveguidesWaveguides are the structures that confines the optical radiation by total internal reflection

Step -index waveguideGraded-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

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Slot WaveguideA 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

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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 sensorJ. 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)

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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.

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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

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TE and TM polarization

1520 nm at TM polarization 1520 nm at TE polarization

Electric field intensity pattern at the output of slot waveguide

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

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Proposed configuration for better confinement of light in slot waveguide

Slot displacement towards inside of bend

Slot displacement towards outside of bend

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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

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Study of relative power in the slot

Normalized relative power restrained in the slot for various slot displacements and bend radius

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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)

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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.

Thank you very much for your attention!!!!

Modelling of TiO2 based slot waveguides with high optical confinement in 90o arc

Muhammad Ali ButtSenior Scientist Science and Research Laboratory of Automated systems of Science Researches,Samara State Aerospace University, RussiaEmail: m.a.butt@ssau.ru

ICECUBE CONFERENCE, 11-12 April 2016Quetta, Pakistan