Hello,
I want to very accurately measure the distance between my microscope objective and my substrate using is an optical fiber sensor from Philtec. In order for the fiber optic to work, the surface has to be specular reflective.
I was thinking of sputtering the coverglass with gold in order to make it reflective, but I'm wondering if the reflection will be specular or diffusive.
Alternatively, could I use thermal evaporation to coat the coverglass with gold and get a surface with specular reflection?
I would greatly appreciate any help.
Thank you.
Hi Rodolfo, as long as the thickness of gold is of the order of 100's of nm you should get a good spectacular reflection, though it can depend a little on your sputtering parameters- deposition rate, target-substrate distance etc. Thermal evaporation works very well but it is a little wasteful. You could also use aluminium, which is MUCH cheaper, but if your sputtering it keep the sputter rate low as it can form a more granular surface otherwise.
Hello Rodolfo,
you have a mirror, if the inhomogenities of the surface are "smaller" then the wavelength. You can test the property of your surface using a laser pointer. If the reflected laser spot gives a defined spot and no intensity distribution, you have a mirror. You can test the laser before, using a high quality mirror. After this you test your gold surface.
Yours
R. Mitdank
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