So it is widely known that the width of the slit affects the interference pattern.  And the double slit experiment is a demonstration of the wave nature of light.  But i could casually see how the thickness of the slits would effect the particle nature of light, if we supposed them as the classical billiard balls.  

**But I looked around and could not find any information relating the effect of the thickness of the slits.**  Depth of the slits, maybe that's better?  The thickness in the direction of photon propagation. 

My first thought would be to explore something that is the thickness on the order of the wavelength.  But i know it would no longer be appropriate to think about it classically.