Download Antireflective Coatings

Coating
Optical coatings are used to alter the reflectance, transmittance, absorbance, or polarizer properties of
optical components. The optics being coated is usually called the substrate. The coating is deposited in
high vacuum using the process of evaporation by either e-beam, resistive heat or IAD (Ion Assisted
Deposition) in conjunction with an e-beam source. We can offer state-of-the-art equipment, advanced
design software and highly experienced engineers to provide you with absolutely the highest level of
support. Coating materials include metal (Au, Al, Ag, Ni-Cr, Cr and so on), dielectrics (Oxides,
Fluorides and Sulfides) and semiconductors (Si, Ge). Optical interference coatings respond differently to
s and p polarized light. For this reason, it is essential to specify s, p, or random (the average of the s and p
performance) polarization when the angle of incidence exceeds 20 degrees.
Now we can provide all kinds of coatings as follows:
Antireflective Coatings
Single Layer MgF2 AR Coatings (SAR)
Multilayer AR Coatings (VAR)
Broadband Multilayer AR Coatings (WAR)
Dual Wavelength Band AR Coatings (DAR)
Partial Reflective Coatings
Single Wavelength Band PR Coatings (SPR)
Broadband PR Coatings (BPR)
Beamsplitter Coatings
Laser Line Polarization Beamsplitter Coatings (LPS)
Broadband Polarization Beamsplitter Coatings (BPS)
Dichroic Beamsplitters Mirrors Coatings (DBS)
High Reflective Coatings
Dielectric High Reflective Coatings (DHR)
Metallic High Reflective Coatings (MHR)
Diode Pumped Laser Optics Coatings (DPC)
Multilayer dielectric coatings consist of stacking, alternatively, high and low index materials. The
thickness of these materials is designed for a specific set of conditions (desired reflective / transmission
values, absorption, angle of incidence and polarization). We can then, by use of optical monitoring
techniques and computer automation of the coater accurately reproduces the desired coating for you.
Besides, we can provide spectral curves from our Perkin-Elmer 900(UV/VIS/NIR) spectrophotometer on
all of our coatings and our coatings meet the Standard Mil Spec tests shown below:
Abrasion, Mil-C-675A
Adhesion, Mil-M-13508C
Hardness, Mil-M-13508C
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Antireflective Coating
Antireflective (AR) coatings increase transmission by reducing surface reflectance losses and improve
image quality by reducing multiple surface reflectance. AR coatings may be applied to many substrate
types such as: Glass, Silicon, Sapphire, Quartz and Others. These coatings can be applied to flat or
curved surfaces such as lenses and spheres.
Now we can provide all kinds of antireflective coatings as follows:
Single Layer MgF2 AR Coatings
Multilayer AR Coatings
Broadband Multilayer AR Coatings
Dual Wavelength Band AR Coatings
Single Layer MgF2 Antireflective Coatings (SAR)
Magnesium fluoride is probably the most widely used thin film material for optical coatings. Its
performance is not outstanding but represents a significant improvement over an uncoated surface
because its index is too high to provide a good impedance match at the air-glass interface.
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Multilayer Antireflective Coatings (VAR)
Such antireflective coatings can reaches the lowest reflectivity at a center wavelength. It is often applied
to single laser wavelength or multiple, closely-spaced wavelength system to guarantee the lowest loss for
center wavelength. We can provide such coating with center wavelength from 250nm to 2200nm. When
selecting a suitable multilayer antireflective coating, the center wavelength and damage threshold must
be paid attention to.
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Multilayer Broadband Antireflective Coatings (WAR)
Different from single layer MgF2 broadband antireflective coating, the multilayer Broadband
antireflective coating can reaches higher transmission for broadband spectrum. Therefore, it is the ideal
for a wide range of multi-wavelength laser and white light application. Please notify that the wavelength
range and reflectivity of the coating are obviously changed according to the incident angle.
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Dual Wavelength Band Antireflective Coatings (DAR)
This coating allows two center wavelengths radiation pass through the substrate with high transmission.
This coating is often used in frequency doubling systems or the other multi-laser output systems, as the
Nd:YVO4 laser (1064nm) and its second harmonic generation (532nm) green laser.
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Partial Reflective Coating
Now we can provide all kinds of partial reflective coatings as follows:
Single Wavelength band Partial Reflective Coatings
Broadband Partial Reflective Coatings
Polarization Beamsplitter Coatings
Single Wavelength Band Partial Reflective Coatings (SPR)
When a narrow wavelength radiation is incident on this coating, part of the radiation is reflected and part
is transmitted. Such coating always shows a high reflectivity for S-polarization radiation and high
transmission for P-polarization radiations. The main application of this coating is to form a beamsplitter
with 45° angle of incident. The non-polarizing beamsplitter plate and cube which are shown in the
chapter "Beamsplitter" are coated with such coatings.
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Broadband Partial Reflective Coatings (BPR)
This coating has similar performance of to that of the Single Wavelength Band Partial Reflective
Coatings, but there is an obvious difference between them. That is, it can be applied to split the incident
radiation over a wide spectrum. The wavelength range of light, partial reflectivity and partial
transmission can be accurately controlled to customer's specifications by our company.
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High Reflective Coating
Now we can provide all kinds of High Reflective Coatings as follows:
Dielectric High Reflective Coatings
Metallic High Reflective Coatings
Diode Pumped Laser Optics Coatings
Dielectric High Reflective Coatings (DHR)
It is well know that dielectric coating can reaches high reflection (more than 99.8% at designed
wavelength can be available by our company) and generally used in single wavelength laser cavity where
the lowest cavity loss at a center wavelength is essential. We can provide such coating with center
wavelength from 250nm to 2200nm according to customer’s special inquiry. When selecting a suitable
dielectric high reflective coating, the damage threshold must be paid attention to.
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Metallic High Reflective Coatings (MHR)
We provide metallic high reflective coatings by material of Au, Ag, Al, Cr, and Ni-Cr. These coatings
are applied to where the consistent high reflection in a wide spectral rang is necessary. Their reflectivity
is not higher than dielectrics HR coatings, but their HR spectrum can over near-UV, visible and near-IR.
In order to prevent these metallic coatings from oxidization, these coatings have been deposited on a
layer of dielectrics coating.
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Diode Pumped Laser Optics Coatings (DPC)
We provide the following coatings for the Nd-Laser application. These coatings are deposited on
substrates of BBO, KTP, Nd:YVO4, Nd:YAG and BK7 and mainly used to Nd Laser and their harmonic
generation.
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Beamsplitter Coating
Now we can provide all kinds of beamsplitter coatings as follows:
Laser Line Polarization Beamsplitter Coatings
Broadband Polarization Beamsplitter Coatings
Dichroic Beamsplitters Mirrors Coatings
Laser Line Polarization Beamsplitter Coatings (LPS)
This coating has special performance of nearly 100% reflectivity for S-Polarization and 100%
transmission for P-polarization at a narrow wavelength bandwidth. Therefore, it main application is to be
used as polarizing beamsplitter in single wavelength laser system when it is deposited on glass substrate.
But its extinction ratio is not so high.
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Broadband Polarization Beamsplitter Coatings (BPS)
It has similar application with Laser Line Polarization Beamsplitter Coating but it can be used in a wide
range spectrum. This spectral range can be controlled by our company according to customer’s special
inquiry.
Dichroic Beamsplitter Mirrors Coatings
The main application of these coating is splitting different wavelength radiation. The DBS-SP coatings
perform high transmission for short wavelength but high reflection for long wavelength, and the inverse
case for DBS-LP coating. The DBS-HP coatings are used to separate harmonic generated lasers. The
following graphics show the contrasted transmission for 1064nm laser and 532nm its second harmonic
laser.
Short Wave Pass Dichroic Beamsplitter Mirror Coatings (DBS-SP)
Long Wave Pass Dichroic Beamsplitter Mirror Coatings (DBS-LP)
Harmonic Separators (DBS-HP)
R>99.8%@1064nm
R<5%@532nm
R>99.8%@532nm
R<5%@1064nm
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Transmision Curve
BK7
BK7 is a borosilicate crown optical glass with high
homogeneity and low bubble and inclusion content. Its
good physical and chemical properties make it widely used
in visible and NIR windows, lenses and prisms.
Transmission range: 330nm ~ 2100nm
Thermal Expansion Coefficient: 7.5 × 10-6/K
Density: 2.51g/cm3
Fused Silica
Fused silica is formed by chemical combination of silicon
and oxygen. Advantages of fused silica material include
good UV and IR transmission, low coefficient of thermal
expansion, providing stability and resistance to thermal
shock over large temperature excursions, wider thermal
operating range and high laser damage threshold. Used for
windows, lenses, prisms and mirror substrates.
Transmission Range: 185nm ~ 2500nm
Thermal Expansion Coefficient: 0.54 × 10-6/K
Density: 2.20g/cm3
Sapphire
Sapphire is a single crystal aluminum oxide or Al2O3 and
is one of the hardest materials, which have good
transmission characteristics over the visible, and near IR
spectrum. Sapphire exhibits high mechanical strength,
chemical resistance and thermal stability. It is often used in
environment where scratch resistance is importance.
Transmission Range: 180nm ~ 4500nm
Thermal Expansion Coefficient: 8.4 × 10-6/K
Density: 3.98g/cm3
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CaF2
CaF2 is a crystal which has good transmission from 170nm
to 7800nm. It is slightly soluble in water and is susceptible
to thermal shock. Common CaF2 uses include IR
components such as windows, lenses and prisms.
Transmission range: 170nm ~ 7800nm
Thermal expansion coefficient: 18.85 × 10-6/K
Density: 3.18g/cm3
Crystal Quartz
Crystal quartz is a positive uniaxial birefringent single
crystal. Our crystal quartz is selected to minimize
inclusions and refractive index variation. Crystal quartz is
most commonly used for high damage threshold
waveplates.
Transmission range: 200nm ~ 2300nm
Thermal expansion coefficient: 7.07 × 10-6/K
Density: 2.65g/cm3
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Optical Materials
We have strong capability in fabricating optical components with various optical materials. The most
important material properties to consider for an optical element are transmission versus wavelength, index of
refraction, thermal characteristics, mechanical and chemical characteristics and cost. There are two instances
in which you might need to know more about optical materials. First, you may need to determine the
performance of a catalog component in a particular application. Second, you may need specific information
when selecting the material for a custom component. The data in the following is intended to assist in these
situations.
To select the right materials seems overwhelming. The simplest way is to let us know your applications, and
we select them for you.
Some of the materials that Our Company uses include:
General Optical Glass
Schott Glass, Ohara Glass
Special Glass
Fused Silica, Color Glass, Float Glass, Zerodur…
Sapphire, CaF2, BaF2, MgF2, LiF, KBr, KCl, NaCl, MgO…
Optical Crystal
Quartz, Silicon, Ge, ZnSe, ZnS, GaAs…
Calcite, YVO4, LiNbO3, BBO, TeO2, LBO, KTP, YAG…
Materials
Refractive Index
Transmission
Range (μm)
Thermal Expansion
Coefficient (10-6/K)
BK7
1.5164 (588nm)
0.330 - 2.1
7.1
SF11
1.78472 (588nm)
0.370 - 2.5
6.1
SF14
1.76182 (588nm)
0.420 - 2.0
6.6
Fused Silica
1.4858 (308nm)
0.185 - 2.5
0.50
CaF2
1.399 (5.0μm)
0.170 - 7.8
18.85
Sapphire
1.755 (1.0μm)
0.180 - 4.5
8.4
Silicon
3.4179 (10 μm)
1.200 - 7.0
2.23
Ge
4.003 (10 μm)
1.900 - 16
5.7
ZnSe
2.40 (10 μm)
0.630 - 18
7.1
ZnS
2.2 (10 μm)
0.380 - 14
6.5
MgF2
no=1.3836 ne=1.3957 (405nm)
0.130 - 7.0
8.8 || c; 13.1 || a
YVO4
no =1.9500 ne=2.1554 (1.3μm)
0.400 - 5.0
11.37 || c; 4.43 || a
CaCO3 (Calcite)
no =1.6557 ne=1.4852 (633nm)
0.210 - 2.3
24.39 || c; 5.68 || a
Quartz
no =1.5427 ne=1.5518 (633nm)
0.200 - 2.3
6.88 || c; 12.38 || a
a-BBO
no =1.6749 ne=15555 (532nm)
0.190 - 3.5
33.3 || c; 0.5 || a
LiNbO3
no =2.2863 ne=2.2027 (633nm)
0.370 - 4.5
4.1 || c; 14.8 || a
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IR Material
Many different types of material will transmit the infra-red. Selection of the most appropriate material is
usually made with reference to the extent of the required transmittance and the nature of the
environments being isolated by the window.
Zinc Selenide (ZnSe), Zinc Sulphide (ZnS), Germanium (Ge) or Gallium Arsenide (GeAs) are
commonly used for the broad IR spectrum including both 3-5µm and 8-14µm bands.
Calcium Fluoride and Magnesium Fluoride are used in the 3-5µm band while maintaining high
transmittance in the visible. Here are some of the commonly available materials:
Material
Transmission Range (μm)
ZnSe
0.68~18.0
ZnS
0.38~14.0
Ge
1.90~16.0
Silicon
1.20~7.00
CaF2
0.17~7.80
MgF2
0.13~7.00
Lens & Windows
Typical diameters offered are: 6.35, 10.0, 12.7, 25.4, 38.1, 50.8, 76.3 and 200mm.
Thickness varies from 1.0 to 6.0 mm as appropriate to maintain the flatness specification.
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