Optical Coatings
Optical Coatings
Optical Coatings
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V-<strong>Coatings</strong><br />
V-coatings are multilayer antireflection coatings that reduce the<br />
reflectance of a component to near-zero for one very specific wavelength.<br />
Our V-coatings are intended for use at normal incidence, for<br />
maximum reflectances of not more than 0.25% at their design wavelength.<br />
They are extremely sensitive to both wavelength and angle of<br />
incidence. For example, a V-coating intended for the helium neon<br />
wavelength (632.8 nm) when used at 30-degree incidence will reflect<br />
about 0.8%. At 45-degree incidence, the same coating will reflect over<br />
2.5%. If your application involves other than normal angles of<br />
incidence or high-numerical-aperture (low f-number) optics, it may<br />
be better to use a HEBBAR coating.<br />
Experience shows that the maximum reflectance typically<br />
achieved by these coatings is often closer to 0.1% than the 0.25%<br />
we specify. Using V-coatings on fused-silica optics can therefore<br />
provide exceptionally high external transmittances.<br />
V-Coating, Normal Incidence<br />
Wavelength<br />
(nm)<br />
193<br />
248<br />
266<br />
308<br />
351<br />
364<br />
442<br />
458<br />
466<br />
473<br />
476<br />
488<br />
496<br />
502<br />
514<br />
532<br />
543<br />
633<br />
670<br />
694<br />
780<br />
830<br />
850<br />
904<br />
1064<br />
1300<br />
1523<br />
1550<br />
Laser Type<br />
ArF<br />
ArF<br />
YAG 3rd harm.<br />
XeCl<br />
Ar ion<br />
Ar ion<br />
HeCd<br />
Ar ion<br />
Ar ion<br />
Ar ion<br />
Ar ion<br />
Ar ion<br />
Ar ion<br />
Ar ion<br />
Ar ion<br />
YAG 2nd harm.<br />
HeNe<br />
HeNe<br />
GaAlAs<br />
Ruby<br />
GaAlAs<br />
GaAlAs<br />
GaAlAs<br />
GaAs<br />
Nd:YAG<br />
InGaAsP<br />
HeNe<br />
InGaAsP<br />
Maximum<br />
Reflectance<br />
(%)<br />
0.5<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
0.25<br />
COATING<br />
SUFFIX<br />
/101<br />
/102<br />
/103<br />
/104<br />
/105<br />
/107<br />
/111<br />
/112<br />
/113<br />
/114<br />
/115<br />
/116<br />
/117<br />
/118<br />
/119<br />
/122<br />
/121<br />
/123<br />
/128<br />
/124<br />
/163<br />
/166<br />
/167<br />
/125<br />
/126<br />
/168<br />
/169<br />
/169<br />
The typical reflectance curve illustrated in figure 5.30 is for a<br />
V-coating on BK7 optical glass. Clearly the performance of such a<br />
coating is highly dependent on the refractive index of the component<br />
material. However, we specify all coatings by performance<br />
figures and not by design. This means that we will change the design<br />
to suit the material being coated. This makes ordering coatings<br />
simple: select the specification you want to achieve, tell us what to<br />
put it on, and we do the rest. This means that your reflectance curve<br />
may vary from the one shown on this page, but the coating will<br />
meet your requirements. In addition to the standard coatings listed<br />
here, Melles Griot can supply V-coatings at any center wavelength<br />
from 193 nm to 2000 nm.<br />
These coatings are not intended for use with high-energy lasers<br />
although the Nd:YAG coatings are suitable for many mediumpower<br />
applications including diagnostics.<br />
PERCENT REFLECTANCE<br />
5<br />
4<br />
3<br />
2<br />
1<br />
normal incidence<br />
typical reflectance curve<br />
550 600<br />
650 700<br />
WAVELENGTH IN NANOMETERS<br />
Figure 5.30 Example of a V-coating for 632.8 nm /123<br />
$ Near-zero reflectance at one specific wavelength<br />
and incidence angle<br />
$ Maximum reflectance often less than 0.1%<br />
$ Standard coatings available for most laser lines<br />
$ Custom center wavelengths at specific angles of incidence<br />
available per request<br />
$ Damage threshold: 4.5 J/cm 2 810%,<br />
10-nsec pulse (361 MW/cm 2 ) at 532 nm for /122 on silica<br />
substrate; 10.6 J/cm 2 810%, 20-nsec pulse (480 MW/cm 2 )<br />
at 1064 nm for /126 on BK7 substrate<br />
Fundamental Optics Gaussian Beam Optics <strong>Optical</strong> Specifications Material Properties <strong>Optical</strong> <strong>Coatings</strong><br />
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