Thorlabs' Coating CapabilitiesThorlabs' state-of-the-art, in-house, optical coating department provides us with coating capabilities ranging from metal coatings and Antireflective coatings to cutting edge Ion Beam Sputtered (IBS) and Plasma Assisted coatings. This full-scale facility not only allows us to produce large numbers of our catalog optics in-house but also expands our ability to manufacture custom-coated optics to suit a variety of customer needs. Coating DesignThe spectral performance and other key characteristics of optical thin films are determined by the structure and number of layers in the coating, the refractive indices of the materials used, and the optical properties of the substrate. The structure of most coatings resembles a series of discrete alternating layers of high index and low index materials. Different arrangements of stack structure result in different types of coatings (e.g., Bandpass vs. Edgepass vs. BBAR). Fine tuning of layer thicknesses and refractive indices is done to optimize performance characteristics in the wavelength range of interest. Thorlabs has a selection of thin film modeling tools to design, characterize, and optimize many aspects of an individual coating's performance. CleaningThe first and one of the most critical steps of our process is cleaning uncoated substrates with an automated ultrasonic clean line. Using a series of ultrasonic solvent and detergent baths, each step of the cleaning process removes different types of contamination from the surfaces of the substrate. This ensures surface contamination does not interfere with adhesion of coatings to the substrate. E-Beam DepositionThorLabs' coating facility currently operates four fully automated Electron Beam (E-Beam) deposition systems. These systems use an electron beam source to evaporate a selection of materials such as transition metal oxides (e.g., TiO2, Ta2O5, HfO2, Nb2O5, ZrO2), metal halides (MgF2, YF3), or SiO2. This type of process must be done at elevated temperatures (200 - 250 °C) to achieve good adhesion to the substrate and acceptable material properties in the final coating. Ion-Assisted E-Beam DepositionIon-Beam Assisted Deposition (IAD) uses the same E-beam method to evaporate coating materials but with the addition of an ion source to promote nucleation and growth of materials at lower temperatures (20 - 100 °C). The ion source allows temperature-sensitive substrates to be coated. This process also results in a denser coating that is less sensitive to spectral shifting in both humid and dry environmental conditions.
IBS DepositionOur Ion Beam Sputtering (IBS) deposition chamber is the most recent addition to our line-up of coating tools. This process uses a high energy, radio frequency, plasma source to sputter coating materials and deposits them on substrates while another RF ion source (Assist source) provides IAD function during deposition. The sputtering mechanism can be characterized as momentum transfer between ionized gas molecules from the ion source and the atoms of the target material. This is analogous to a cue ball breaking a rack of billiard balls, only on a molecular scale and with several more balls in play. Advantages of IBS- Better Process Control
- Wider Selection of Coating Designs
- Improved Surface Quality and Less Scatter
- Reduced Spectral Shifting
- Thicker Coating in a Single Cycle
MetrologyThorlabs uses a selection of research-grade spectroscopy instruments to characterize coating performance from the UV to the Far Infrared. Varian Cary 5000 and PE Lambda 950 spectrophotometers are used to characterize the spectral performance of our coatings in the UV-VIS-NIR ranges and an Olis PE 983 IR spectrophotometer is used for infrared coatings (2 - 55.5 µm). In addition to the spectroscopy tools, we also use a variety of laser and laser diode sources, our power meters and detectors, as well as our polarimeter series to test the performance of our optics. We build custom setups to test both catalog and OEM parts to ensure every optic we offer performs well within the specified range. All of our metrology instruments are calibrated regularly per ISO9001:2000 standard.
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Laser Line/Bandpass FiltersLaser Line and Bandpass filters transmit light in a narrow, well-defined spectral region while rejecting other unwanted radiation. This type of filter displays very high transmission in the bandpass region and blocks a limited spectral range of light on either side of the bandpass region. To compensate for this deficiency, an additional blocking component is added, which is either an all-dielectric or a metal-dielectric depending on the requirements of the filter. Although this additional blocking component eliminates any unwanted out-of-band radiation, it also reduces the filter's overall transmission throughput. These coatings are formed by vacuum deposition coating techniques and consist of two reflecting stacks, separated by an even-order spacer layer. These reflecting stacks are constructed from alternating layers of high and low refractive index materials, which can have a reflectance in excess of 99.99%. By varying the thickness of the spacer layer and/or the number of reflecting layers, the central wavelength and bandwidth of the filter can be altered. Edgepass FiltersEdgepass filters are very useful for isolating specific spectral regions. Longpass filters transmit wavelengths longer than the cutoff wavelenght and block wavelengths shorter than the cutoff wavelength. Shortpass filters block wavelengths longer than the cutoff wavelength and transmit those shorter than the cutoff wavelength. All Thorlabs edgepass filters are constructed of durable dielectric coatings and will withstand the normal cleaning and handling associated with any high-quality optical component. Their film construction is essentially a modified quarter-wave stack, using interference effects rather than absorption to isolate their spectral bands. Dichroic BeamsplittersDichroic Beamsplitters are used as beam directors at 45° and are either longpass or shortpass. The longpass variety reflects >90% of the incident light below the design wavelength and transmits >90% of the incident light above the design wavelength. The shortpass variety transmits below the design wavelength, and reflects above the design wavelength. Dichroic beamsplitters are used in many applications, the most common one being fluorescence microscopy. The dielectric coating on dichroic beamsplitters is the source of their functionality. The alternating layers in the coating are designed to cause constructive interference for those wavelengths to be transmitted and destructive interference for those wavelengths to be reflected. The thickness of the coating and the refractive index of the materials in the layers determine the design wavelength for a given beamsplitter. Notch FiltersNotch filters, also commonly referred to as band-stop or band-rejection filters, are designed to transmit most wavelengths but attenuate light within a specific wavelength range (the stop band) to a very low level. They are functionally the inverse of bandpass filters and are made in the same way. Neutral Density FiltersNeutral Density (ND) filters attenuate all wavelengths within a range by a certain factor to prevent damage to detecting equipment. Fixed ND filters attenuate the spectra by a fixed amount. Variable ND filters have stepped films at discrete locations to allow for various attenuation depending on the application. Continuous ND filters have a film gradient across the entire filter, which allows for a continuous range of attenuation. Thorlabs offers a selection of both linear and circular variable and continuous ND filters. |
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Antireflective (AR) coatings are hard refractory-oxide coatings that minimize surface reflections within specified wavelength ranges when applied to the surface of optical components. Without AR coating, 4% of the light is lost at each optical surface due to reflections. The drawing below illustrates the functionality of AR coatings. If three uncoated lenses are being used in series, 4% of the incident light is lost at each of the six surfaces. This results in a total loss of 21.7%. With an AR coating, the reflection is reduced to <0.5% per surface. If three AR-coated lenses are being used instead, the total loss of incident light due to surface reflections is <3%. The use of AR-coated optics improves transmission from 78.3% to greater than 97% in this case. Please note that the 4% loss at the interfaces of uncoated optics is an approximate value that varies greatly with material and AOI. Click on the bars in the graph below to view the performance plot for each AR Coating. 
Broadband antireflective (BBAR) coatings consist of multiple layers, alternating between a high index material and a low index material. The layers are deposited on the substrate via electron-beam deposition. The thickness of the layers is optimized, using modeling software, to produce destructive interference between reflected waves and constructive interference between transmitted waves. This results in an optic that has enhanced performance within a specified wavelength band as well as minimal internal reflections (ghosting). Thorlabs' BBAR coatings are designed for angles of incidence between 0° and 30° and a numerical aperture (NA) of 0.5. Thorlabs currently offers AR coatings designed to maximize performance within 7 different wavelength ranges. V-coatings are multilayer, dielectric, thin-film, AR coatings that are designed to minimize reflectance over a short wavelength range. Surface reflectance rises rapidly on either side of this minimum, which gives the reflectance curve a "V" shape. Compared to the broadband AR coatings, V-coatings achieve lower reflectance over a narrower bandwidth when used at an incident angle between 0° and 20°. We currently offer 3 different V-coatings. These coatings perform at their best at an AOI from 0 to 20°. | V-Coating Specifications |
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| Name | Wavelength Range | Average
Reflectivity* | Performance
Plot | | 633 nm | 555 - 705 nm | <0.25% | | | 780 nm | 700 - 850 nm | <0.25% | | | YAG | 450 - 600 nm
1000 - 1150 nm | <0.25% | |
*The reflectivity is measured over the specified wavelength range and then averaged. A small defect in the coating will not affect the overall average reflectivity. | AR Coating Specifications |
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| Coating Code | Wavelength Range | Average
Reflectivitya | Performance
Plotb | Coating
Variationc | | UV | 290 - 370 nm | <0.5% | | Unavailable | | A | 350 - 700 nm | <0.5% | |  | | B | 650 - 1050 nm | <0.5% | | | | C | 1050 - 1620 nm | <0.5% | | | | D | 1.8 - 3 µm | <1.0% | | Unavailable | | E | 3 - 5 µm | <2.5% | | Unavailable | | F | 8 - 12 µm | <1.5% | | Unavailable |
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High-reflection (HR) coatings are hard, refractory, oxide coatings that maximize surface reflections within a specific wavelength range and angle of incidence. They are essentially the opposite of AR coatings. The coating consists of alternating layers of high and low index materials. The layer's thickness is optimized, using computer models, to produce constructive interference for reflected waves and destructive interference for all other wavelengths. The reflectivity of the surface is improved greatly by the addition of an HR coating; however, its performance is dependent on the angle of incidence (AOI). At high AOIs, the reflection band shifts to shorter wavelengths and performs differently for S and P polarizations. Thorlabs currently offers eight different HR coatings optimized for various performance parameters. The E01, E02, E03, and E04 dielectric HR coatings offer high reflectance over broad wavelength ranges. The Protected Silver coating has the highest reflectance in the visible spectrum of all of our metalic coatings. Silver is susceptible to oxidation so the surface is protected with an overcoat of SiO2. The Protected Aluminum coating is an inexpensive solution for general use. The surface is also protected with an overcoat of SiO2 to make the aluminum coat suitable for laboratory and industrial use. Our UV-Enhanced Aluminum coating has an overcoat of MgF2 to increase the average reflectance in the UV portion of the spectrum. Finally, the Protected Gold coating is the most efficient metallic coating over the entire IR range. Thorlabs uses an overcoat to protect the gold surface and to make the mirror easy to clean. The table below contains key specifications and reflectance plot for each of our HR coatings. | HR Coating Specifications |
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| Coating Name | Wavelength Range | Average Reflectivitya
| Laser Damage Thresholdb | Performance Plotc | Coating Variationd | | E01 | 350 - 400 nm | >99% | 1 J/cm2 at 355 nm,
Ø0.373 mm pulsed beam,
10 ns pulses @ 10 Hz. | | Unavailable | | E02 | 400 - 750 nm | >99% | 0.25 J/cm2 at 532 nm,
Ø0.803 mm pulsed beam,
10 ns pulses @ 10 Hz. | |  8° AOI 45° AOI | | E03 | 750 - 1100 nm | >99% | 1 J/cm2 at 810 nm,
Ø0.133 mm pulsed beam,
10 ns pulses @ 10 Hz. | | 8° AOI 45° AOI | | E04 | 1280 - 1600 nm | >99% | 2.5 J/cm2 at 1542 nm,
Ø0.181 mm pulsed beam,
10 ns pulses @ 10 Hz. | | Unavailable | | UV Enhanced Aluminum | 250 - 450 nm | >90% | 0.3 J/cm2 at 355 nm,
Ø0.38 mm pulsed beam,
10 ns pulses @ 10 Hz. | | Unavailable | | Protected Aluminum | 450 nm - 20 µm | >90% (450 nm - 2 µm)
>95% (2 - 20 µm) | 0.3 J/cm2 at 1064 nm,
Ø1.00 mm pulsed beam,
10 ns pulses @ 10 Hz. | | Unavailable | | Protected Silver | 450 nm - 20 µm | >97.5% (450 nm - 2 µm)
>96% (2 - 20 µm) | 3 J/cm2 at 1064 nm,
Ø1.00 mm pulsed beam,
10 ns pulses @ 10 Hz. | | | | Protected Gold | 800 nm - 20 µm | >96% | 2 J/cm2 at 1064 nm,
Ø1.00 mm pulsed beam,
10 ns pulses @ 10 Hz. | | |
aThe reflectivity is measured over the specified wavelength range and then averaged. A small defect in the coating will not effect the overall average reflectivity.
bAll diamaters are the 1/e2 vlaues.
cThe shaded regions in all plots represent the specified wavelength range for optimum reflectivity.
dOptical coatings vary from run to run. The specifications provided throughout our website are true for all coating runs. However, these plots give you some idea of the variation that does occur. For a complete selection of Thorlabs' HR-coated optics, plese click the button below.
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Optical SubstratesThorlabs offers a wide variety of optical substrates that are ideal for use in various applications. The graph to the right compares the transmission ranges of the 10 most common substrates we offer. Below is information and key properties for these substrates. To quickly navigate through these substrates use the Table of Contents listed below. If you have questions about a substrate not described here, please contact Technical Support as they will be able to assist you. Table of Contents| N-BK7 Specifications |
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| Index of Refraction | | | Index of Refraction Equation |  | | Abbe Number (Vd) | 64.17 | | Density | 2.51 g/cm3 | | Knoop Hardness (100 g Load) | 520 kg/mm2 | | Young's Modulus | 863 GPa | | Shear Modulus | - | | Bulk Modulus | 34 GPa | | Poisson's Ratio | 0.208 | | Coefficient of Thermal Expansion | 86 x 10-7 | | Heat Capacity | 0.858 J/(g*K) | | Softening Point | 550°C | | Change in Index of Refraction with Temperature | 2.4 x 10-6/°C |
N-BK7 is borosilicate crown glass. It is a hard glass that can withstand a variety of stressors. It does not scratch easily and it is also fairly chemically resistant. It will maintain its optical properties even when exposed to numerous chemicals. N-BK7 also has a low bubble and inclusion content. It is transparent from 350 nm to 2.0 µm. The index of refraction of N-BK7 is 1.52 at 0.55 µm. | Spherical Lenses | Plano-Convex | Uncoated, Unmounted | | Uncoated, Mounted | | V-Coated | | A Coated (350-700 nm), Unmounted | | A Coated (350-700 nm), Mounted | | B Coated (650-1050 nm), Unmounted | | B Coated (650-1050 nm), Mounted | | C Coated (1050-1620 nm), Unmounted | | C Coated (1050-1620 nm), Mounted | | Bi-Convex | Uncoated | | A Coated (350-700 nm) | | B Coated (650-1050 nm) | | C Coated (1050-1620 nm) | | Plano-Concave | Uncoated | | A Coated (350-700 nm) | | B Coated (650-1050 nm) | | C Coated (1050-1620 nm) | | Bi-Concave | Uncoated / AR Coated | | Best Form | Uncoated | | A Coated (350-700 nm) | | B Coated (650-1050 nm) | | C Coated (1050-1620 nm) | | Positive Meniscus | Uncoated / AR Coated | | Negative Meniscus | Uncoated / AR Coated | | Cylindrical Lenses | Plano-Convex | Round | | Uncoated | | A Coated (350-700 nm) | | B Coated (650-1050 nm) | | C Coated (1050-1620 nm) | | Plano-Concave | Round | | Uncoated | | A Coated (350-700 nm) | | B Coated (650-1050 nm) | | C Coated (1050-1620 nm) | | Windows | Non-Wedged | Uncoated / AR Coated | | V Coated | | Wedged | V-Coated | | Beamsplitters | Non-Polarizing Cubes | 400 - 700 nm, Unmounted | | 700 - 1100 nm, Unmounted | | 1100 - 1600 nm, Unmounted | | Mounted | | Prisms | Retroreflectors | Uncoated / AR Coated, Unmounted | | Uncoated / AR Coated, Mounted | | Right Angle | Uncoated / AR Coated | | Dove | Uncoated | | Penta | Unmounted | | Mounted | | Roof | Uncoated | | Wedged | AR Coated | | Pellin Broca | Uncoated | | Fresnel Rhomb Retarder | Uncoated | | Windows | High Precision | Uncoated / AR Coated | | Laser | V Coated | | Wedged | Uncoated / AR Coated | | Conductive | Coated | | Polarizers | Economy | Unmounted | | Diffusers | Ground Glass | Unmounted / Mounted |
| UV Fused Silica Specifications |
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| Index of Refraction | | | Index of Refraction Equation | | | Abbe Number (Vd) | 67.8 | | Density | 2.203 g/cm3 | | Knoop Hardness (100 g Load) | 500 kg/mm2 | | Young's Modulus | 71.7 GPa | | Shear Modulus | 30 GPa | | Bulk Modulus | 37 GPa | | Poisson's Ratio | 0.17 | | Coefficient of Thermal Expansion | 5.5 x 10-7 | | Heat Capacity | 54.3 J/(mol*K) | | Softening Point | 1665°C | | Change in Index of Refraction with Temperature | 11.9 x 10-6/°C |
UV Fused Silica is transparent over a wide range of wavelengths: 185 nm - 2.1 µm. It is scratch resistant, and has a low coefficient of thermal expansion. This material does not fluoresce when exposed to wavelengths longer than 290 nm. It is ideal for UV applications. The index of refraction of UV Fused Silica is 1.46 at 0.55 µm. | N-SF11 Specifications |
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| Index of Refraction | | | Index of Refraction Equation | | | Abbe Number (Vd) | 25.68 | | Density | 4.74 g/cm3 | | Knoop Hardness (100 g Load) | 450 kg/mm2 | | Young's Modulus | 92 GPa | | Shear Modulus | 37 GPa | | Bulk Modulus | - | | Poisson's Ratio | 0.235 | | Coefficient of Thermal Expansion | 6.8 x 10-6 | | Heat Capacity | 0.710 J/(g*K) | | Softening Point | - | | Change in Index of Refraction with Temperature | - |
N-SF11 is transparent from 420 µm to 2.3 µm. Its index of refraction is 1.79 at 0.55 µm. With a high index of refraction and a low Abbe number, N-SF11 has high dispersive power and is ideal for applications in the visible range that require high dispersion. | Calcium Fluoride Specifications |
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| Index of Refraction | | | Index of Refraction Equation | | | Abbe Number (Vd) | 94.99 | | Density | 3.18 g/cm3 | | Knoop Hardness (100 g Load) | 158.3 kg/mm2 | | Young's Modulus | 75.8 GPa | | Shear Modulus | 33.77 GPa | | Bulk Modulus | 82.71 GPa | | Poisson's Ratio | 0.26 | | Coefficient of Thermal Expansion | 19 x 10-6 | | Heat Capacity | 0.7 J/(g*K) | | Meltinging Point | 1360°C | | Change in Index of Refraction with Temperature | -10.6 x 10-6/°C |
Calcium Fluoride is transparent from the UV to the IR (180 nm - 8.0 µm). It has a low refractive index of 1.399 at 5 µm and is mechanically and environmentally stable. It is ideal for demanding applications where its low damage threshold, low fluorescence, and high homogeneity are beneficial. It is frequently used in spectroscopy and cooled thermal imaging. | Barium Fluoride Specifications |
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| Index of Refraction | | | Index of Refraction Equation | | | Abbe Number (Vd) | 81.61 | | Density | 4.893 g/cm3 | | Knoop Hardness (100 g Load) | 182 kg/mm2 | | Young's Modulus | 53.05 GPa | | Shear Modulus | 25.4 GPa | | Bulk Modulus | 56.4 GPa | | Poisson's Ratio | 0.343 | | Coefficient of Thermal Expansion | 19.9 x 10-6 | | Heat Capacity | 0.40 J/(g*K) | | Meltinging Point | 1550°C | | Change in Index of Refraction with Temperature | - |
Barium Fluoride is transparent from the UV to the IR (200 nm - 11 µm). It is less resistant to water than Calcium Fluoride and is very sensitive to thermal shock. This substrate is relatively hard and, of all of the substrates Thorlabs offers, it is the most resistant to high-energy radiation. Barium Fluoride has an index of refraction of 1.45 at 5 µm. | Sapphire Specifications |
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| Index of Refraction | | | Abbe Number (Vd) | 72.4 | | Density | 3.98 g/cm3 | | Knoop Hardness (100 g Load) | 1370 kg/mm2 | | Young's Modulus | 335 GPa | | Shear Modulus | 148 GPa | | Bulk Modulus | 240 GPa | | Poisson's Ratio | 0.25 | | Coefficient of Thermal Expansion | 5 x 10-6 | | Heat Capacity | 0.75 J/(g*K) | | Meltinging Point | 2300°C | | Change in Index of Refraction with Temperature | 13.1 x 10-6/°C |
Sapphire is transparent in from the UV to the IR (150 nm - 6 µm) and is extremely hard and chemically stable. Its hardness allows it to be made much thinner than other substrates. This substrate is commonly used in IR laser systems and has an index of refraction of 1.77 at 0.55 µm. | Silicon Specifications |
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| Index of Refraction | | | Index of Refraction Equation | | | Abbe Number (Vd) | N/A | | Density | 2.329 g/cm3 | | Knoop Hardness (100 g Load) | 1100 kg/mm2 | | Young's Modulus | 130.91 GPa | | Shear Modulus | 79.92 GPa | | Bulk Modulus | 101.97 GPa | | Poisson's Ratio | 0.28 | | Coefficient of Thermal Expansion | 2.6 x 10-6 | | Heat Capacity | 0.84 J/(g*K) | | Meltinging Point | 1690°C | | Change in Index of Refraction with Temperature | 1.6 x 10-6/°C |
Silicon (Si) lenses and windows are an ideal choice for applications using wavelengths from 1.2 - 8.0 µm. They are particularly well suited for imaging, biomedical, and military applications. Silicon has an index of refraction of 3.42 at 10.6 µm. | Zinc Selenide Specifications |
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| Index of Refraction | | | Index of Refraction Equation | | | Abbe Number (Vd) | N/A | | Density | 5.27 g/cm3 | | Knoop Hardness (100 g Load) | 105 kg/mm2 | | Young's Modulus | 70 GPa | | Shear Modulus | - | | Bulk Modulus | 40 GPa | | Poisson's Ratio | 0.28 | | Coefficient of Thermal Expansion | 7.1 x 10-6 | | Heat Capacity | 0.34 J/(g*K) | | Meltinging Point | 1790°C | | Change in Index of Refraction with Temperature | 61 x 10-6/°C |
Zinc Selenide (ZnSe) is transparent from 600 nm - 16 µm and is ideal for IR applications. Due to its low absorption coefficient at 10.6 µm, it is well suited for high-power CO2 laser applications. ZnSe also transmits some visible light, unlike Germanium and Silicon, thereby allowing for visual optical alignment. ZnSe has an index of refraction of 2.4 at 10.6 µm. It is commonly used in thermal imaging and carbon dioxide laser systems. | Germanium Specifications |
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| Index of Refraction | | | Index of Refraction Equation | | | Abbe Number (Vd) | 600 | | Density | 5.33 g/cm3 | | Knoop Hardness (100 g Load) | 800 kg/mm2 | | Young's Modulus | 102.66 GPa | | Shear Modulus | 67.04 GPa | | Bulk Modulus | 77.86 GPa | | Poisson's Ratio | 0.278 | | Coefficient of Thermal Expansion | 6.1 x 10-6 | | Heat Capacity | 0.31 J/(g*K) | | Meltinging Point | 1210°C | | Change in Index of Refraction with Temperature | 396 x 10-6/°C |
Germanium (Ge) is transparent in the IR region from 2.0 µm to 16 µm, making it an ideal substrate choice for biomedical and military imaging applications in this part of the spectrum. Ge has an index of refraction of 4.00 at 10.6 µm. It is commonly used in thermal imaging. | Magnesium Fluoride Specifications |
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| Index of Refraction | | | Index of Refraction Equation | | | Abbe Number (Vd) | 106.22 | | Density | 3.18 g/cm3 | | Knoop Hardness (100 g Load) | 415 kg/mm2 | | Young's Modulus | 138.5 GPa | | Shear Modulus | 54.66 GPa | | Bulk Modulus | 101.32 GPa | | Poisson's Ratio | 0.276 | | Coefficient of Thermal Expansion | 14 x 10-6 | | Heat Capacity | 1.26 J/(g*K) | | Meltinging Point | 1528°C | | Change in Index of Refraction with Temperature | 1.7 x 10-6/°C |
Magnesium Fluoride is transparent over a wide range of wavelengths. Transmitting from 200 nm to 6.0 µm, this substrate can be used in applications in the UV to IR range. It is very rugged and durable, making it useful in high-stress applications. Magnesium Fluoride has an index of refraction of 1.41 at 0.27 µm. It is commonly used in machine vision, microscopy, and industrial applications.
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Optical Coating Capabilities
