Hi,

I am a optics student. Brewster's angle measurement is also a good
reliable technique in measuring the index. I have done it very
recently. At brewster's angle your reflected power goes to almost
zero. Input light should be TM polarized i.e horizontle polarized.

regards,
kamal

On Sat, 14 Aug 2004 21:22:45 -0400, sxy154  wrote:
> Hello Xianling
> You might want to try prism coupling technique to measure the refractive
> index of film. The basic assumption of this method is you already know exact
> thickness of film. Even thought, this technique is widely used for thin film
> rather than thick film, I don't see any restriction in thickness range.
>
> Good Luck
>
> Sung
>
>
>
> -----Original Message-----
> From: X Chen [mailto:[email protected]]
> Sent: Friday, August 13, 2004 7:12 PM
> To: [email protected]
> Subject: [mems-talk] refractive index measurement of thick films
>
> Hello MEMS talkers,
>
> Does anyone know a way to measure refractive index of thick films? I used
> spectrophotometer to measure the VIS spectral transmission of 50 micron
> SU-8 on Borofloat wafer. However, the transmittance modulation is just too
> weak for reliable index fitting. With a large film thickness, light
> coherence is lost due to finite bandwidth and surface vaiation. Reducing
> film thickness to a few microns using SU-8 thinner will solve this problem
> but I doubt the index will be different. I need to have a precise
> dispersion curve (index vs. wavelength) for optical devices. The index
> mentioned in publised papers varies greatly and is available only for a
> few individual wavelengths. This index variation could be caused by
> different processing conditions. Therefore, the index should ideally be
> measured for my own process. But I would appreciate if someone can give me
> a dispersion curve for SU-8 in VIS-NIR range.
>
> Best regards,
>
> Xianling Chen
>
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--
"Its better to lose your pride for someone you love,
 than to lose that someone you love for your useless pride"

"Whether it happens in a hundred years or a thousand years or a
million years, eventually our sun will grow cold and go out. When that
happens, it won't just take us. It'll take Marilyn Monroe and Lao-Tzu
and Einstein and Morobuto and Buddy Holly and Aristophanes... and all
of this... all of this was for nothing, unless we go to the stars. -
Commander Sinclair, "Infection" "

Kamal Yadav
Graduate Student
Rose Hulman Institute of Technology
Terre Haute
Indiana 47803