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Material - Zinc Selenide ZnSe CVD
ZnSe is used for optical windows, lenses, mirrors, prisms and optical blanks, plates, disks, sheets, slabs particularly for infrared applications
Zinc Selenide (ZnSe) - transparent in wide spectral range from yellow (visible) to far IR. ZnSe material is a chemically inert, non-hygroscopic and highly pure product that is very effective in many optical applications due to its extremely low bulk losses, high resistance to thermal shock and stability in virtually all environments, easily machined. To obtain superior transmittance, ZnSe crystals are grown by Chemical Vapor Deposition process (CVD). Zinc Selenide CVD is polycrystalline material, demonstrates superior CO2 laser transmittance and is employed in the transmission optical components used in CO2 laser processing.
ZnSe (Zinc Selenide) Chemical Vapor Deposition (CVD) material is produced by synthesis from zinc vapour and H2Se gas, forming as sheets on graphite susceptors (ZnSe-CVD processes). Chemical purity of CVD-ZnSe 99.999%. It has à polycrystalline structure; the grain size of Zinc Selenide CVD material is controlled to produce maximum strength and machinability.
The transmission range of Zinc Selenide ZnSe-CVD is (0.5 – 20) microns. ZnSe CVD used for high power CO2 laser optics at 10.6 microns, for protective optics windows or optical elements in FLIR (forward looking infrared) thermal imaging equipment, optics for medical and industrial applications (optical plane parallel windows (plates, disks, sheets, slabs, blanks), wedged windows, Brewster windows, optical meniscus, spherical and cylindrical lenses, prisms, resonator mirrors of CO2 laser).
Single crystal ZnSe Zinc Selenide is available, but is not common, it has lower bulk losses and thus more effective for CO2 optics.
Crystaltechno Ltd.
- grows Zinc Selenide (ZnSe) CVD ingots with size up to 270 mm x 500 mm, thickness up to 20mm, transparent during the spectral range (0.5– 20) microns.
- manufactures from Zinc Selenide ZnSe CVD the following optics
blanks, windows, protective windows, wedges, cylindrical and spherical lenses, meniscus, right angle prisms, ATR prisms, CO2 optics, resonator mirrors for CO2 laser at 10.6 microns, Brewster windows, domes, spherical microlenses, balls and hemisphere, ZnSe witness samples. These products are particularly for infrared applications including CO2 laser optics.
- offers Evaporation Grade Zinc Selenide ZnSe-CVD (size less than or equal to 6 mm, purity: 99.999%)
Perhaps you’ll find required ZnSe optics at our stock, please see item Optical Crystals.
Our company has a full cycle manufacturing of ZnSe optics from simple chemicals to finished optic with coating and offers all the products within this line including semi-finished items.
Along with Zinc Selenide growth material (sheets, SMTY) we offer blanks cut to custom size, inspection polished sheets. Our facility allows to produce standards CO2 optics such as plano-convex ZnSe lenses and meniscus, output ZnSe windows.
At the same time we offer wide range of custom designs optics with complex shape such as FLIR windows with profiled mounting grooves, hemisphere domes, hyperhemisphere domes where ZnSe transmission is perfect for multichannel optical devices.
Complex shape and profiled ZnSe optics is made using advantages of CVD technology which provides best ZnSe prices and quality.
ZNSE (ZINC SELENIDE) BASE PROPERTIES
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PARAMETER |
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VALUE |
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| PHYSICAL PROPERTIES of Zinc Selenide (ZnSe) |
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Density |
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5.27 g/cm3 |
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Melting Point |
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1525°C (dissociates about 700°C) |
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Thermal Conductivity |
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18 W/(m K) at 298K |
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Thermal Expansion |
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7.1 x 10-6/°C at 273K |
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Hardness Knoop, with 50 g indenter, kg/mm2 |
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120 |
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Specific Heat Capacity |
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339 J/(kg K) |
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Young's Modulus (E) |
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67.2 GPa |
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Bulk Modulus (K) |
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40 GPa |
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Apparent Elastic Limit |
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55.1 MPa (8,000psi) |
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Poisson Ratio |
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0.28 |
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Resistivity |
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~1012 (Ohm x cm) |
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| CHEMICAL PROPERTIES of Zinc Selenide ZnSe CVD |
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Solubility |
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0.001 g/100g water |
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Molecular Weight |
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144.33 |
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Crystal Structure |
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polycrystalline
ZnSe (CVD) Laser grade, grain size (50-70) microns
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| OPTICAL PROPERTIES of ZnSe Zinc Selenide CVD |
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Transmission Range |
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(0.5– 20) microns |
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Refractive Index |
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2.4028 at 10 microns |
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Reflection Loss |
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31.11% at 10.6 µm (2 surfaces) |
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dn/dT |
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+61 x 10-6/°C at 10.6µm at 298K |
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dN/dµ = 0 |
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5.5µm |
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Index of Absorption |
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ZnSe-CVD Laser grade 0.0005 (1/cm) at 10.6 microns
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ZNSE (ZINC SELENIDE) REFRACTIVE INDEX
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Wavelength, µm |
2.75 |
5.00 |
7.50 |
9.50 |
11.0 |
12.5 |
13.5 |
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Refractive Index |
2.44 |
2.43 |
2.42 |
2.41 |
2.40 |
2.39 |
2.38 |
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Wavelength, µm |
15.0 |
16.0 |
16.9 |
17.8 |
18.6 |
19.3 |
20.0 |
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Refractive Index |
2.37 |
2.36 |
2.35 |
2.34 |
2.33 |
2.32 |
2.31 |
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TRANSMISSION of UNCOATED and AR/AR COATED ZNSE OPTICS
Because of high refractive index (n = 2.4 at 10.6 microns), calculated Fresnel losses of Zinc Selenide polished surface are equal 17% (at one side), thus the transmission (T) of ZnSe polished window equals T = 68.9 % at 10.6 micron (without absorption). Note all calculations are done for wavelength of CO2 laser 10.6 microns leaving out of account the possible multiple internal beam reflections.
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If ZnSe window is a plane parallel plate and laser beam with good divergence (plane wave) incidences perpendicularly to a ZnSe window surface (normal incidence), in this case we must take into account subsequent multiple internal beam reflections inside of ZnSe plate. So transmission (Tw) of a uncoated ZnSe window subject to multiple reflections (5 times) will be 1.03 times more, namely Tw = 70.9% (without absorption). Hence Reflection Loss in this case equals 29.1%. Even if one of mentioned above conditions is absent, transmission of Zinc Selenide window will equal T = 68.9 % at 10.6 micron (without absorption). As to another wavelength 13.5 microns refractive index n = 2.38, so T = 69.4% (without absorption) and Tw = 71.4% (without absorption). You can see spectrum transmission chart of ZnSe window below.
Spectral Transmittance (T) of ZnSe Uncoated Polished Window (thick. 10mm), range (2.5–25) microns
Usually consideration of internal multiple reflections inside of ZnSe detail is not necessary for a ZnSe lens and a ZnSe wedge, because the lens strongly changes a beam divergence, and wedge directs reflected beam out of main optical axis. Hence as a rule transmission of uncoated ZnSe wedge and ZnSe lens equals T = 68.9 % at 10.6 micron (without absorption). So we have considered a ZnSe optics transmission without taking into account radiation absorption and scattering inside Zinc Selenide material.
As to bulk absorption of ZnSe optics, it’s necessary to consider and calculate value of absorbed power for high power CO2 lasers and CO2 laser machines, because ZnSe optics may be heated and distorted as result of high power radiation absorption.
Crystaltechno Ltd produces CVD grown ZnSe (Zinc Selenide) material with low absorption, namely index of absorption of Zinc Selenide material equals 0.0005 (1/cm) at 10.6 microns. For example we calculate the bulk transmission (Tb) of 1 cm thickness (ZnSe material) as Tb = exp (- 0.0005 x 1), Tb = 0.9995 or 99.95% at 10.6 microns. This value must be considered in calculation of real transmission for ZnSe optical components.
Crystaltechno Ltd offers two sides antireflection (AR/AR) coating both for one wavelength (10.6 microns or another) and for the spectral range (3 – 12) microns. Transmission of AR/AR coated CVD Zinc Selenide window - up to 99% at 10.6 microns.
We produce optics from CVD grown ZnSe laser grade material with the following characteristics: grain size (50-70) microns, index of absorption 0.0005 (1/cm) at 10.6 microns. Zinc Selenide optical components dimensions - (3 – 100) mm, thickness 20mm. ZnSe optics is used in high power CO2 laser systems, in medical applications and thermal imaging equipment.
You can order the different ZnSe optics from CVD ZnSe material.
Crystaltechno Ltd. offers the manufacturing of ZnSe optics (in detail please see Catalog):
- ZnSe windows (round and rectangular windows, plane parallel plates, protective windows and plates)
- ZnSe wedges (wedged windows)
- ZnSe spherical lenses, ZnSe cylindrical lenses, ZnSe meniscus lenses
- CO2 laser optics: AR/AR coated ZnSe plane parallel windows, AR/AR coated ZnSe wedges, ZnSe Brewster windows, AR/AR coated ZnSe meniscus lenses, ZnSe output couplers (partial reflector or output mirror)
- ZnSe prisms: ZnSe right angle prisms, ZnSe Dove prisms, ZnSe ATR prisms, ZnSe ATR hemispheres (ATR - Attenuated Total Reflection)
- Different Zinc Selenide optical blanks, custom cut-to-size blanks, sheets with inspection polishing, SMTY (Sufficient Material To Yield) material and leftovers from CVD grown ZnSe material, namely: ZnSe unpolished blanks, plates, planks, bits, pieces, ingots, disks, ZnSe sheets, bars, slabs, ZnSe raw material, ZnSe growth crystal, ZnSe SMTY material or SMTY optical blanks, ZnSe waste.
Perhaps you’ll find required ZnSe optics at our stock, please see item Optical Crystals.
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