Importance of Project

1

• Cost
• Fixed fee 6,250.00
• Per layer cost 8 x ( 375.00)
• Substrate 67.50
• Hourly costs
• Technician
• Substrate cleaning 0.5 x ( 120.00)
• Preparation of 8 layers 4.0 x ( 120.00)
  
• Depreciation 4.5 x (
  250.00)
• Machine activation 120.00
• TOTAL COST 11,102.50
• Bandwidth 112 nm
• Center wavelength 550 nm
• Maximum oscillation error 22
• Number of layers Coupling top, 3 Stacks,
  Coupling bottom
• TOTAL 8
• Thickness of layers

Specifications
TEAM NAME
At present time different types of filters
are known. Each of them has its own advantages
and disadvantages. Band-pass filters are one of
the simplest and most economical ways to reflect
a well-defined band of electromagnetic waves and
transmit all others. The main purpose of this
project was to develop an optical quarter-wave
stack reflection filter with 100 reflectance at
a central wavelength of 550nm, and a narrow
bandpass. Furthermore, optimal results had to be
met with minimum design cost. Another project
goal was to optimize both, the number of layers,
and the thickness of each layer. Using the
design parameters above, team IBM of LaserDyne
created an 8 layer filter composed of a coupling
top, coupling bottom, and three stacks. Lithium
Fluoride and Zinc Sulfide were chosen as the
materials for the layers. The goal of optimizing
cost was achieved in two ways. First, using only
three stacks allowed for 95 reflectance on the
bandpass filter. Second, the bandwidth of 112nm
was optimized at 50 reflectance by adjusting the
thickness of each layer. Also, the maximum
oscillation error was found to be 22.
Overview

• The actual and theoretical results our design
  team calculated had some discrepancies. The
  theoretical design results were as follows (see
  graphs below)
• Reflectance 93.5 at central wavelength of
  550nm
• Bandwidth of the filter is 256nm
• Actual results were obtained after many
  manipulations and improvements on the design gave
  us (see graphs on the right)
• Reflectance 95 at central wavelength is 550nm
• Bandwidth of the filter is 112nm
• The maximum oscillation error is 22 at ? 672nm
  
• Number of layers is 8
• The total cost of the design is 11,102.50
• Weakness
• The major weakness of the filter design is the
  oscillations around the base line of the graph.
  The design team worked hard to reduce them to the
  level that they are at now. The team feels that
  we could reduce the damping of those oscillations
  to zero if given more time and resources to work
  on the design.
• Future Work
• The future work on this design would allow the
  design team to dampen the oscillations around the
  outside of the filtered range. Also, given more
  resources we could build prototypes of the design
  and actually take measurements to see how the
  filter works outside of the MATLAB simulation.
  FIGURES ????

Results
Importance of Project It allows us, the workers
of LaserDyne, to demonstrate why our design will
meet the demands of our client. As a team, it
gives up the opportunity to prove our worth in
the company by developing a solution that is
chosen to be the best solution among the
LaserDyne teams. Previous Work The design team
analyzed several web sites. (refer to reference
page) From these web sites simplified design
equations for an optical quarter-wave stack
reflection filter were found, and allowed the
design team to know what is currently state of
the art as well as industry standards. Approach
and Methodology After reviewing MATLAB tutorials
and doing extensive research on quarter wave
stacks, the team used equations for calculating
the thickness needed to fulfill the goals of the
project. In 1 it was recommended to use the
filter structure which consists of identical
layers of high and low refractive indexes. Next
part was to calculate their thicknesses.
According to 2 phase change on reflection must
be considered. This phase shift of 1800 ?0/2.
The distance 2?d ?/2 (? is wavelength in a
layer) and ? ?0/n, then 2?d ?0/(2?n). It means
that the thickness of the layer should be d
?0/(4?n). Each film (layer) has an optical
thickness of ? /4 for maximum reflectance.
Development of Specifications The various
characteristics the team thought to be important
and that were considered in determining the best
solution were (1) cost, (2) the minimization of
delta ?, (3) the percentage of reflectance, and
(4) the accuracy of the bandpass filter in
respect to the center wavelength.
Background
1 Multilayer Structures (n.d.). Retrieved
October 16, 2003, from http//webraft.its.unimelb.
edu.au/208102/pub/ewa/ch05.pdf 2 Guenther A.,
Pedrotti L., Roychoudhuri C. (n.d.). Thin-film
interference. Retrieved October 15, 2003, from
http//agamemnon.cord.org/step_online/st1-4/st14ei
ii3.htm
For theoretical results, we found the thickness
(d), and reflectance (G1) using the equations
below. It can be seen that the theoretical
results do not fully satisfy the goals set out
for this project.
References
nH zinc sulfide nL lithium fluoride na
air nb glass N of stacks
n index of reflection (nL, nH) ?0 550nm