AR colors and wavelenghts

[essegn]

Hi,

Could anybody advice what wavelenght of AR layers correspond with red color?

Purple - 560 nm
Green - 480 nm
Blue - 530 nm
Red - ??? nm

Thank you.

[mauroventura]

Hi essegn.
I dont' know what you mean as 'AR layers colors' ,but if you speak about the 'AR residual reflection color' then please look this image and take inspiration ;).






Mauro Ventura

[essegn]

Thank you.

But i would like to have similar spectrum, but not Color vs Wavelenght as you sent, but Refraction vs Wavelenght..

I hope it is clear now :)

Because, i summed the particular thicknesses at our AR coating machine and the sum of thicknesses are not relative to the wavelenght in the visible spectrum you sent.

[Comma]

Why summed up ?
I don't really understand.
Each layer does its job mostly individually.
Maybe I'm wrong....

Just as a reminder :

thickness of the layer = wavelenght/4n

Wavelenght of red = 700 nm
n is the refraction index of the material you use :
MgF2 : 1.38
AlO2 : 1.65
SiO : 2.00
ZnS : 2.30
TiO2 : 2.35
And so on...

[essegn]

Maybe i'm wrong..

I try to explain my intension. We have AR coating machine and we bought processes with the following colors of reflection:

- green
- purple
- blue

I would like to create the new process with red color of reflection. As i was taught the color of refraction is depending on layer thickness.

I would like to change one of our process (thicknesses of particular layers - SiO, AlO2...) in order to get red color of refraction.

The sum of the thicknesses for green color of reflection is 480nm, for purple is 560 nm etc.

I don't know exactly how it works, but i think that if i know the sum of thicknesses of particular layers for red color of reflection, i will be able to modify one of our process to get red color..

[Falstaff]

Unfortunately, it is more complicated than that. You have to take into account the interference between rays of light reflecting (and multiply reflecting) between all the interfaces of all of the layers. This is, in general, a very complex calculation, but there are computer programs out there which will give you a good idea what will happen if you make a change to any of the layer thicknesses.

If you change all of the thicknesses by the same factor, you can achieve a sort of 'shift' of the whole spectral curve to the right or the left. The reflex colour may be adjusted to a certain extent by this method, but if the curve has steep edges on the sides, it is well to keep them at wavelengths where the eye is less sensitive. You can also change the colour a little by engineering a deliberate tilt to the curve. We can do this by adjusting the thickness of the final SiO2 layer.

Best Regards,

Falstaff

[Mauro.Airoldi]

It's like Falstaff see... it's more complicate than that....
I was process engineer in Satisloh for 10 years and belive me, modify AR coating it's not a play.
In any case the summa of the thickness don't mean nothing. it' s trouble connec with material index, thickness, layer sequency ...
More, if you cange the thickness or sequency it can be you modify the mechanical propety of the AR coating (hardness, termal stress resistance ....).
my suggestion is DON'T TOUCH , call the supplier ;-)

[essegn]

Does anybody know about good AR calculator ? Because i found one, but i don't trust it.

We have also the machine for checking quality of AR layer so i can see direct results from test, not only reflection color.

In case, that i contact supplier they would tell me to buy a new process :)

My ex colleague found the new process with blue reflection color, by adding the thickness of Ti-Al-Oxide mainly.

I believe that if i know the sum of thicknesses for red reflection color i will be able to do that.

Which reflection color are most popular except green, purple and blue ?

[Mauro.Airoldi]

The best simulator software is Macleod http://www.thinfilmcenter.com/
The "machine for checking...." it is a spettrophotometer
But belive me play arround AR coating is not so esy

[mudmagnet]

Listen to this guy , he really does know what he is talking about, changing the reflex colour can be a very difficult excersise.

Also why does anyone wish for red reflex , for sure performance wise there are benefits, Zeiss did this many moons ago on hi index mineral.

Stick with what the market requires.

Mauro I am the guy in uk you know very well, ciao.

[Georg Mayer]

To sum it up, to tackle this you need

a) Years of training and experience in AR stack design
b) A Layer calc program you can trust
c) A Spare AR machine to play

Stay away if you dont have a) and b) and c) and lots of time plus
plenty of hair to tear out on frequent occasions when it doesn't happen
as the layer calc said..... ;-)

Georg Mayer
Better Best then Biggest

Munich - Germany

[Rafael]

Leybold Optics has a good calculation software

TFCalc is also useful, there is also a demo version: http://www.sspectra.com/

But you will need a spectrophotometer, without it is very hard. You can get an older used Perkin-Elmer on ebay for about 400-700$.
I also use an old Perkin-Elmer, works fine for me. Ok there are new systems with laptops and much smaller, but about 10000-15000€.

[essegn]

We have the new spectrofotometer from them..

I'm wondering to have gold mirror. We have bought the only "silver" one and i'm wondering if it is necessary to change the only thicknesses or the Ti3O5 for another "gold" material.

Could you help me out ?

[Rafael]

Send you all you need via pm, which software you use for calculating?