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Chemically
vapor deposited zinc selenide (CVD ZnSe) is the material of choice
for use as optical components in high powered CO2 lasers due to its
low bulk absorption at 10.6 microns. Its index of refraction homogeneity
and uniformity offers excellent optical performance for use as protective
windows or optical elements in high resolution forward looking infrared
(FLIR) thermal imaging equipment. This material has also been used
as small windows and lenses in medical and industrial applications,
such as thermometry and spectroscopy. It has an extremely low bulk losses
due to absorption and scatter, has a high resistance to thermal shock
and is stable in virtually all environments.
Zinc selenide is a relatively soft material and scratches
rather easily. It requires an antireflection coating due to its high
refractive index if high transmission is required. ZnSe has a rather
low dispersion across its useful transmission range. For high power
applications, it is critical that the material bulk absorption and
internal defect structure be carefully controlled, that the minimum-damage
polishing technology be employed, and that the highest quality optical
thin film coatings are used. |
Optical
Properties
| Crystal structure |
cubic |
| Grain size |
50 - 70 µm |
| Density,
g cm-3 @ 298K |
5.27 |
| Chemical
Purity, % |
99.999 |
| 10% transmission
limits (t=6mm) |
0.5 - 22
µm |
| Index of
refraction inhomogeneity (Dn/n), ppm @ 0.6328µm |
< 3 |
| Thermo-optic
coefficient, dn/dT(298-358K), 1/K @ 0.6328µm |
1.07 x 10-4 |
| (1/K
@ 1.15µm) |
7
x 10-5 |
| (1/K
@ 3.39µm) |
6.2
x 10-5 |
| (1/K
@ 10.6µm) |
6.1
x 10-5 |
| Bulk absorption
coefficient, 1/cm @ 1.3µm |
5.0 x 10-3 |
| (1/cm
@ 2.7µm) |
7.0
x 10-4 |
| (1/cm
@ 3.8µm) |
4.0
x 10-4 |
| (1/cm
@ 5.25µm) |
4.0
x 10-4 |
| (1/cm
@ 10.6µm) |
5.0
x 10-4 |
Indices of
Refraction (n) as a function of wavelength
at room temperature (20°C)
| Wavelength
(µ) |
n |
Wavelength
(µ) |
n |
Wavelength
(µ) |
n |
Wavelength
(µ) |
n |
| 0.54 |
2.6754 |
1.80 |
2.4496 |
7.40 |
2.4201 |
13.00 |
2.3850 |
| 0.58 |
2.6312 |
2.20 |
2.4437 |
7.80 |
2.4183 |
13.40 |
2.3816 |
| 0.62 |
2.5994 |
2.60 |
2.4401 |
8.20 |
2.4163 |
13.80 |
2.3781 |
| 0.66 |
2.5755 |
3.00 |
2.4376 |
8.60 |
2.4143 |
14.20 |
2.3744 |
| 0.70 |
2.5568 |
3.40 |
2.4356 |
9.00 |
2.4122 |
14.60 |
2.3705 |
| 0.74 |
2.4518 |
3.80 |
2.4339 |
9.40 |
2.4100 |
15.00 |
2.3665 |
| 0.78 |
2.5295 |
4.20 |
2.4324 |
9.80 |
2.4077 |
15.40 |
2.3623 |
| 0.82 |
2.5193 |
4.60 |
2.4309 |
10.20 |
2.4053 |
15.80 |
2.3579 |
| 0.86 |
2.5107 |
5.00 |
2.4295 |
10.60 |
2.4028 |
16.20 |
2.3534 |
| 0.90 |
2.5034 |
5.40 |
2.4281 |
11.00 |
2.4001 |
16.60 |
2.3487 |
| 0.94 |
2.4971 |
5.80 |
2.4266 |
11.40 |
2.3974 |
17.00 |
2.3438 |
| 0.98 |
2.4916 |
6.20 |
2.4251 |
11.80 |
2.3945 |
17.40 |
2.3387 |
| 1.00 |
2.4892 |
6.60 |
2.4235 |
12.20 |
2.3915 |
17.80 |
2.3333 |
| 1.40 |
2.4609 |
7.00 |
2.4218 |
12.60 |
2.3883 |
18.20 |
2.3278 |
Deliveries from ground blanks to finished as well as processed optical elements are possible.
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