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Abstract
Three one dimensional photonic crystals (lDPCs) which can be
applied as optical low pass filters are designed and fabricated to act as
infrared shield films. The devices block infrared light and pass only light
composed of short wavelengths. The one dimensional photonic crystal
(lDPC) is formed from alternate layers of optical thin films consisting of
high (Ti02) and low (Si02) refractive index materials. The first design
(Filter I) consists of a quarter wave stack of periodic multi layer structure.
The design of the second filter (Filter 2) consists of three stacks of thin
films, the first laminated stack has an optical film thickness greater than
the optical film thickness of the second stack. A third laminate is
interposed between the two laminates with an optical film thickness that
is less than the first laminate thickness and greater than the second
laminate thickness in order to suppress the ripples in the stop band of the
infrared region. The design of the third filter (Filter 3) uses a first stack
that has an optical film thickness less than that of the second stack.
Modeling these crystals has been carried out using the transfer matrix
method (TMM). An Open source code (OpenFilters simulation software)
was used and it was checked against our own MA TLAB code for
consistency and accuracy. Ion Assisted Deposition (lAD) Technique was
used to deposit the proposed filters on fused silica substrates.
Transmission greater than 90% in the visible region and reflection greater
than 99% in the infrared region has been obtained. Studying the
transmission of the first filter at different angles of incidence of light (for
both TE, TM modes and also for unpolarized light) may provide other
applications for this filter. Filter 1 has a great potential be used as a self
tuned smart window at hot climate regions in the northern hemisphere
such as Egypt.