Is the light visible light or X-rays or other light?

If it's visible light, then I would say use something with a lot of diffraction, so high density and transparent object, glass would be good.

If it's X-ray light, then something high density but low atomic number would be good, like diamond by it self, or diamond with epoxy is a good thing to use. You could get some cheap industrial diamond for a dollar each.

You might consider a well characterized oxide that has been measured by ellipsometry. You could then pattern the material with photolithography.  You can make the features large enough for 10 x objective.  I think you could do this with SiO2 on silicon, or SiN on silicon pretty easily, or deposited on fused silica or sapphire. The you should have relatively good reference samples. 

You might be able to just do the same with just photoresist, the refractive index is pretty well characterized and you can spin at different RPM to make objects of the same refractive index of different thicknesses.  

You may find that purchasing some diffractive optics for lasers can be done for a few dollars. they were quite popular for a while for laser pointers, but the features may be too small for your 10 x objective.

Hello Chandrabhan,

does your microscope measure the actual phase of some coherent light, or does it just use phase difference for contrast (as in DIC microscopy or similar)? And is it a transmission or reflection microscope?

Just some ideas of inexpensive samples to test:

- If you are measuring the actual phase of the light in reflection, a starting quick experiment can be performed using a mirror as your sample, as you move the focus you should see a spherical phase pattern of varying curvature, which becomes flat when the mirror is in the focal plane.

- If you are measuring the actual phase of the light in transmission, you can put any thin glass lens in (for example you can often find free bookmarks with thin lenses "incorporated") and look at the curvature of the lens thickness.

- Finally, if you are using interference just for contrast, any semitransparent sample looks better with it: the thin lens cleaning paper that probably you have in the lab will look nice. Alternatively, you can use any kind of spray on a microscopy slide for making small droplets, which should look very three dimensional under interference contrast.

Hi Paolo,

Thanks for your inputs. The microscope I have developed is measuring the actual phase of the light in transmission using interference for contrast. I have used broadband light LED with 550nm band-pass filter, hence, the coherence length is very small compared to leaser light. 

What do you think about water sample in a cavity slide?

Regards

Hello Chandrabhan,

that sounds actually quite impressive, i'm looking forward to see a publication from you about your microscope :)

If you have a cavity slide small enough, that's a good idea, maybe you can use the same slide with air, water and microscopy oil, and try to measure the differences in refractive index.

Another possibility is trying with some cheap diffraction grating paper, you should be able to see the step and phase difference in the grating, and compare it to the specifications, if any are provided (something like this: http://www.ebay.com/itm/Diffraction-Grating-Roll-Sheet-Linear-1000-lines-mm-Laser-Holographic-Spectrum-/280859388704).

Good luck with your experiment!

Hi Christina,

Thanks for the suggestion. I would probably try this.