- #1
Ngineer
- 64
- 1
Hello everyone,
We are trying to fabricate a copper layer that is 41% reflective to a beam of 1521nm wavelength.
The formula I have used to calculate the thickness is:
R = 1 - e-αt
Where
R: desired reflectance of mirror
t: thickness of mirror that would produce said reflectance
α: material- and wavelength-specific absorption coefficient. (for copper at 1521nm: α = 8.4327e+5 cm-1, from http://refractiveindex.info/?shelf=main&book=Cu&page=Rakic)
For these values, I get t=6.25nm. When they fabricated it at the lab, there was almost no reflection at all.
Is the formula wrong? I based it on the transmission of a mirror being approximately T=e-αt and R being 1-T for a mirror. Is there a siginificant amount of energy absorbed by the copper itself?
Your help is highly appreciated.
We are trying to fabricate a copper layer that is 41% reflective to a beam of 1521nm wavelength.
The formula I have used to calculate the thickness is:
R = 1 - e-αt
Where
R: desired reflectance of mirror
t: thickness of mirror that would produce said reflectance
α: material- and wavelength-specific absorption coefficient. (for copper at 1521nm: α = 8.4327e+5 cm-1, from http://refractiveindex.info/?shelf=main&book=Cu&page=Rakic)
For these values, I get t=6.25nm. When they fabricated it at the lab, there was almost no reflection at all.
Is the formula wrong? I based it on the transmission of a mirror being approximately T=e-αt and R being 1-T for a mirror. Is there a siginificant amount of energy absorbed by the copper itself?
Your help is highly appreciated.