We have designed and fabricated the low-polarizing X-plate to increase the luminous throughput for
LED projector. We calculate reflectivity characteristic of X-plate as a function of the wavelength at
different angles of incidence from air of unpolarized light. A new way to design filter to control the
title effect of thin film filters. The wavelength shift of the new design for reflected red filter and
reflected blue filter at the angle of 45° ± 8° is 16 nm and 14 nm, respectively.
An optical system to extract the reflection coefficient and optical admittance of film stack is presented. Both reflection
phase and reflection magnitude intensity from the tested film stack were measured under normal incidence of the light.
Two dimensional refractive index and thickness distribution of each layer in multilayer thin films can be obtained by the
analysis of the reflection coefficients or optical admittance of multi-wavelengths. A novel monitoring method for the thin
film deposition using the reflection coefficient and optical admittance loci as the thickness grows is also proposed to
achieve better performance in this article.
Normally metallic films are required for solar energy and display related coatings. To increase the absorbing
efficiency or contrast, it is necessary to apply an antireflection coating (ARC) on the metal substrate. However, the
design of a metal substrate is very different from the design of a dielectric substrate, since the optical constant of metallic
thin film is very dependent on its thickness and microstructure. In this study, we design and fabricate ARCs on Al
substrates using SiO2 and Nb2O5 as the dielectric materials and Nb for the metal films. The ARC successfully deposited
on the Al substrate had the following structure: air/SiO2/Nb2O5/Metal/Nb2O5/Al. The measured average reflectance of
the ARC is less than 1% in the visible region. We found that it is better to use a highly refractive material than a low
refractive material. The thickness of the metallic film can be thicker with the result that it is easier to control and has a
lesser total thickness. The total thickness of the ARC is less than 200 nm. We successfully fabricated a solar absorber
and OLED device with the ARC structure were successfully fabricated.
Nb doped TiO2 (TNO) is a promising transparent conducting oxide suitable for many applications such as in solar cells,
OLEDs, LEDs, FPDs, touch panels, etc. TNO thin film was deposited on an unheated glass substrate by pulsed direct
current (DC) magnetron co-sputtering. After annealing in a vacuum (<9×10-6 Torr) at 370° for 10 minutes, the film
crystallized into a polycrystalline anatase TiO2 structure, the resistivity decreased to 4.5×10-4 Ω-cm and the average
transmittance increased to above 70% in the visible light region. The influence of annealing on the TNO
amorphous-to-anatase phase transition, decrease in the resistivity and increase in the average transmittance will be
discussed.
We have designed and fabricated angle-selective filters to increase the luminous throughput of a blue light emitting diode
(LED) and its associated color wheel. The emission direction was tailored to increase the light emission in the useful
direction by using multilayer optical coating with alternating high and low refractive indices layers. The angle selective
filters limit the luminance angle to less than an acceptance angle of 30 degrees for green and red on the phosphors color
wheel. The filters increase the luminance efficiency by converging and recycling the light. The color performance of the
phosphors color wheel was improved and gave an advantage of energy saving in the LED projector.
Transparent conducting Fluorine-doped tin oxide (FTO) thin films were deposited on glass substrates by pulsed DC
magnetron sputtering from cost saving metal targets. We observed lower resistivity and higher average transmittance in
the visible range after the application of various post heating treatments. The electrical and optical properties of FTO
films were investigated. When the annealing temperature is 400°C in air, the average transmittance is 79.79% with the
lowest resistivity of 1.38×10-3 Ω-cm, carrier density of 2.27×1020 cm-3 and mobility of 20 cm2/ V-s. When the annealing
temperature is 400°Cin a H2 5%+N2 95% atmosphere, the average transmittance is 79.75 % with the lowest resistivity of
1.26×10-3 Ω-cm, carrier density of 2.17×1020 cm-3 and mobility of 22.8 cm2/ V-s. When the annealing temperature is 350 °C in vacuum, the average transmittance is 80.48% with the lowest resistivity of 1.23×10-3 Ω-cm, carrier density of
4.40×1020 cm-3 and mobility of 11.6 cm2/ V-s.
Thin films of tungsten oxide (WO3) were deposited on GZO-coated B270 glass substrates and thin films of Ta2O5 were
deposited on B270 glass substrates by electron beam gun evaporation at high vacuum pressure of 3×10-5 Torr and varied
oxygen pressures ranging from 1.0×10-4 to 6.0×10-4 Torr. The optical properties of the electro-chromic (EC) film were
measured by a spectrophotometer. The optical modulation (ΔT) of the tungsten oxide thin film deposited at an oxygen
pressure of 1.0×10-4 Torr was found to be ΔT = 67.46% at λ=550nm. The optimum optical properties for deposition of
Ta2O5 were attained at an oxygen pressure of 4x10-4 Torr. Gallium doped zinc oxide (GZO) was used as a conductive
layer instead of ITO. A five layer EC device (Glass/GZO/WO3/Ta2O5/NiO/Al) has been design and fabricated.
The well-known indium-tin-oxide is not suitable for solar cell, because of the chemical reduction, even
without any hydrogen dilution. The inexpensive and non-toxic of transparent conducting Aluminum and
Gallium doped ZnO (AZO and GZO) thin films have been investigated for the substitutes for the
indium-tin-oxide thin films. AZO performs high transmittance at visible region, however, higher resistance
than GZO. In this study, AZO and GZO composed film (GAZO) will be fabricated using DC magnetron
co-sputtering deposition system to achieve lower resistance than AZO and higher transmittance than GZO.
The optical and electric properties of different thickness of GAZO such as transmittance, reflection, carrier
concentration, Hall mobility, and resistivity will be measured and analyzed.
Dense-wavelength-division-multiplexing (DWDM) filter is a very sensitive component in wavelength shift. The
temperature shift of central wavelength (TSCW) of filter is depended on the mechanical properties of the stress. In this
paper, a modified Stoney's equation was applied to analyze the thermal stress of DWDM filters for the reason of the
thickness ratio (thin film thickness/substrate thickness) larger than 1%. The phase-shift interferometer and TSCW were
applied to measure and achieve the coefficient of thermal expansion (CTE), biaxial modulus, temperature optical
coefficient, stress optical coefficient, and Poisson ratio of DWDM filter. Based on this method, we can obtain the CTE of
DWDM filter 0.87pm/ °C ,the biaxial modulus 41 GPa, Poisson ratio 0.22, temperature optical coefficient 1.4×10-5 / °C, and stress optical coefficients -1.9×10-12 /Pa. To achieve zero TSCW for a DWDM filter, the CTE of the substrate should be 10.36ppm/ °C.
Autocloning technique is an attractive deposition method to make photonic crystals since it can produce various photonic crystals by changing the substrate periodicity and the structure of the stacking materials. We report a novel method to fabricate autocloned photonic crystals. This method has better step-coverage, higher deposition rate and large deposition area than the sputtering method. We successfully preserved the periodic surface corrugation after the deposition of multilayer stacks by using an E-beam gun evaporation with ion-assisted deposition (IAD). Freedoms of the shaping process can be controlled by the power of IAD and the time of the ion source etching. The ion source etching is a physical etching process without any chemical reaction and dangerously reactive gas. The process parameters were described in this paper. During the deposition process, the refractive index can be adjusted by changing the deposition rate and the substrate temperature. The deposition rate was about 0.7~1 nm/s for SiO2 which is almost ten times faster than the sputtering method. So this method is good for the mass production of photonic crystals.
Dense Wavelength Division Multiplexers (DWDM), a kind of narrow band-pass filter, are extremely sensitive to the optical thickness error in each composite layer. Therefore to have a large useful coating area is extreme difficult because of the uniformity problem. To enlarge the useful coating area it is necessary to improve their design and their fabrication. In this study, we discuss how the tooling factors at different positions and for different materials are related to the optical performance of the design. 100GHz DWDM filters were fabricated by E-gun evaporation with ion-assisted deposition (IAD). To improve the coating uniformity, an analysis technique called shaping tooling factor (STF) was used to analyze the deviation of the optical thickness in different materials so as to enlarge the useful coating area. Also a technique of etching the deposited layers with oxygen ions was introduced. When the above techniques were applied in the fabrication of 100 GHz DWDM filters, the uniformity was better than +/-0.002% over an area of 72 mm in diameter and better than +/-0.0006% over 20mm in diameter.
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