Radius of Curvature: 900 micron

1
MIAMI UNIVERSITY CENTER FOR NANOTECHNOLOGY
Modeling Fabrication of Ridge Waveguides and
their Comparison to Photonic Bandgap
Structures Kathleen Beddow, Meron Tekeste,
Senthil Rajagopal, Jan M. Yarrison-Rice, Physics
Department, Miami University
Modeling Waveguides
Introduction Optoelectronics is a field of
technology involving the study and fabrication of
microelectronic devices that interact with light
(photons). An optoelectronic device either
contains or acts as a transducer, a device that
converts between electrical and optical signals.
This technology provides the capacity to
generate, transport, and manipulate data at
exceptional rates. Our study focuses upon the
characterization of both waveguides, specifically
the Ridge Waveguide, and Photonic Bandgap
Structures with a goal to be able to fabricate
the waveguides in house.

• Fabrication of Ridge Waveguide
• The fabrication of the Ridge Waveguide will be
  done through UV photolithography followed by
  immersion of a slab waveguide in a dilute
  hydrofluoric acid (HF) solution for wet etching.
• Although the HF solution will etch both the Si3N4
  and SiO2, selectivity for the Si3N4 can be
  increased by increasing the dilution of the HF
  solution. In doing this however, the etch rate is
  sacrificed, some of which may be regained through
  elevation of temperature.
• PBG structure will be fabricated via e-beam
  lithography and plasma etching.

Fig. 4 Waveguide Modeling at 632.8nm
wavelength a.) Straight Slab Waveguide Light
Propagation with High Power Loss b.)Straight
Ridge Waveguide (1.3 micron Ridge) Light
Propagation with Minimal Power Loss c.)S-Ridge
Waveguide, Curve of Radius 900 micron Light
Guidance d.) S-Ridge Waveguide, Curve of
Radius 13 micron Light Loss

• Total Internal Reflection
• Total Internal Reflection occurs as light travels
  from a higher to a lower index of refraction
  when the refracted angle is equal to 90o or
  greater, which depends on the angle of incidence.

b.)
a.)

• Optical Waveguide
• Waveguide Structural component of integrated
  optical circuits having the ability to guide high
  frequency electromagnetic waves due to different
  indices of refraction.
• Ridge Waveguide A slab waveguide with a Ridge
  etched into the upper substrate, changing the
  effective indices of refraction on either side,
  creating conditions for Total Internal Reflection
  within the ridge area allowing for guidance of
  light.

Radius of Curvature 900 micron

• Experimental Characterization of Waveguide
• Once fabrication has occurred, the waveguide
  will be characterized by measuring the input and
  output power. This will allow us to determine the
  amount of light escaping as it travels down the
  waveguide.

Radius of Curvature 13 micron
Fig. 7 Setup for Measuring Light Transmission
through Waveguide

• Photonic Bandgap Structures (PBG)
• Photonic Bandgap Structure Substrate (e.g.
  Silicon Nitride) etched with periodic array of
  air pores is used to create a photonic lattice.

Modeling PBG

• Summary
• We are studying the field of optoelectronics in
  an effort to model both ridge waveguides and
  photonic bandgap structures.
• In examining the properties of these waveguides
  and PBG structures, their ability to guide and
  contain light will be examined and compared.
• In addition to modeling ridge waveguides, the
  goal is to be able to fabricate these structures
  within our facilities. This will be done through
  an wet etching process with HF.
• Once fabricated our waveguides will be
  characterized through a series of measurements to
  show their effectiveness in containing light.

Fig. 5 Triangular Lattice PBG Modeling at
632.8nm wavelength a.) Triangular Lattice
Straight PBG Structure Minimal Light Loss, 92
Transmission b.) Triangular Lattice Curved PBG
Structure Minimal Light Loss, 94 Transmission
a.)
b.)
R 75nm
a 257nm
Fig. 3 a.) Triangular Lattice of PBG b.)
Dispersion Graph