Modelling Interference Filter Performance Using Zemax and Encrypted Coatings Files
@yahoo.co.uk Jarvis
(near 1.5 um) in a non-normal incidence configuration. Additionally, the
light incident on the filters can have varying amounts of non-random
polarization. This variation in incident polarization will have an effect
on the amounts of "s" and "p" polarization that the filter experiences. As
a result, the amount of transmitted light will vary because of the differing
filter transmission characteristics for "s" and "p" polarized light.
I'm using Zemax as a design tool and trying to estimate/calculate the
effects polarization variation on system performance. Zemax has the
capability of importing coatings files from thin film design programs like
Essential McLeod in an encrypted format (i.e. files have ZEC extension) that
protect the coater from having his intellectual property being reversed
engineered. Alternately, I could use a reasonable description of filter
characteristics for "s" and "p" polarization as a function of incidence
angle.
So, it seems like all the engineering design tools are in place. However, I
seem to be having trouble finding a filter/coating vendor willing to supply
these encrypted coatings files. Nor can I find one who is willing to supply
representative "s" and "p" transmission vs. angle characteristics. I'm
certainly willing to purchase custom designed filters but not without a
knowledge of these transmission characteristics.
Has anyone been through this before with any success? Can you recommend
capable vendors?
Sincerely,
John
Helpful person
I wouldn't expect any vendor to let you have coating files, encrypted
or not. Encryption is usually very easy to break. However, I would
expect them to supply you with data for s and p reflectivity of their
present filters. After all, when they deliver a filter measured data
is usually included. (If you need "unusual data" you could offer to
pay for it.)
Have you tried Omega Optical, Chroma Technology, Lambda Research,
Optisigma or Barr?
Boxman
You could try having an independent consultant do a film design for
you and pay for the design so that you have the coating files. You
could then find a vendor to make the part per your designed recipe.
JK consulting is one company I'm aware of that will do this kind of
work. http://www.kruschwitz.com/
Salmon Egg
"Jarvis" <john.jarvis @ yahoo.co.uk> wrote:
> So, it seems like all the engineering design tools are in place. However, I
> seem to be having trouble finding a filter/coating vendor willing to supply
> these encrypted coatings files. Nor can I find one who is willing to supply
> representative "s" and "p" transmission vs. angle characteristics. I'm
> certainly willing to purchase custom designed filters but not without a
> knowledge of these transmission characteristics.
I went through something like this before retiring. The company I was
dealing with was very reluctant to pass on the design of a coating they
were using. They had paid for the design and did not want to give it
away. Finally, when they realized that I was not trying to steal
anything, I was able to find out what their design was. My memory of it
is not all that sharp.
The coating, IIRC, was the equivalent of V antireflection coatings at
two wavelengths for neodymium lasers and its second harmonic. The
vendors design used seven layers while mine used only four. That
indicated to me that the designer was not all that sharp. Moreover, even
with four layers, at least dozens would meet the requirements. To select
out of these, I examined what the maximum field strength would be in the
"weakest" material.
My suggestion is to use one of the optimizing thin-film programs.
Initial configurations for narrow band filters are available in many
places. Start with them.
Try to find out the optical properties of the materials they like to
use. They may be less reluctant to reveal those.
Bill
Helpful person
I wouldn't recommend using an independent consultant. It is fairly
easy to design a coating "on paper" with specific properties but takes
a lot more skill and experience to design one that can be
manufactured. In addition, designs can be specific to a particular
company's equipment. By this I mean that a design may work well for
one company but may need considerable changes to work for another.
It's a bit of a black art.
However, you could pay a coating company to develop a coating for you
to the feasibility stage. This cost (which should not be too high for
feasibility) would then be absorbed if you later had them make it for
you.
mp...@oscintl.com
John:
Check out bookham and semrock for these types of narrow band filters.
Most coating firms will supply filter performance with s, p, and
average performance versus wavelength and also versus angle of
incidence, if they wont go elsewhere.
Since you are using Zemax you should know about the tablecoating way
to model thin films. The table coating will allow you to model the s,
p refl and transmission and absorption, based upon the coating curves
from different vendors, you can then assign this coating performance
to your surfaces and trace the rays and look at the various optical
transmission, reflection, and image or illumination system
performance. Very cool feature and the way many advanced systems are
analyzed for total performance, especially when you can't get the
actual thin film designs.
Michael
www.oscintl.com
@yahoo.co.uk Jarvis
<mp...@oscintl.com> wrote in message
news:b7be4f20-752f-4f5a...@1g2000prf.googlegroups.com...
On Mar 21, 8:46 am, "Jarvis" <john.jarvis @ yahoo.co.uk> wrote:
> I'm working on a project that uses narrow bandpass interference filters
> (near 1.5 um) in a non-normal incidence configuration. Additionally, the
> light incident on the filters can have varying amounts of non-random
> polarization. This variation in incident polarization will have an effect
> on the amounts of "s" and "p" polarization that the filter experiences. As
> a result, the amount of transmitted light will vary because of the
> differing
> filter transmission characteristics for "s" and "p" polarized light.
<<snip>>
> Has anyone been through this before with any success? Can you recommend
> capable vendors?
>
> Sincerely,
>
> John
John:
Check out bookham and semrock for these types of narrow band filters.
Most coating firms will supply filter performance with s, p, and
average performance versus wavelength and also versus angle of
incidence, if they wont go elsewhere.
Since you are using Zemax you should know about the tablecoating way
to model thin films. The table coating will allow you to model the s,
p refl and transmission and absorption, based upon the coating curves
from different vendors, you can then assign this coating performance
to your surfaces and trace the rays and look at the various optical
transmission, reflection, and image or illumination system
performance. Very cool feature and the way many advanced systems are
analyzed for total performance, especially when you can't get the
actual thin film designs.
Michael
www.oscintl.com
Thanks Michael. I have been estimating filter performance using the table
coating method. I agree, it is a pretty cool way to go about it.
Thanks for the vendor recommendation.
Sincerely,
John