r/Optics • u/Lonely-Competition-5 • 9h ago
Repeatable interference pattern using two flat glass plates and a custom liquid mixture – expected thin-film interference or something worth investigating?
Hello everyone,
I observed a repeatable interference pattern using a very simple setup, and I’m interested in understanding whether this is just a known thin-film interference effect or if the specific implementation is technically interesting.
Setup:
Green laser pointer
Two ordinary flat glass plates
A thin layer of a custom liquid mixture (3–4 components) between the plates
Projection on a distant screen
Observations:
Without the liquid, the characteristic ring pattern does not appear.
With this specific liquid mixture, a stable concentric ring pattern appears after about one minute and is repeatable.
Changing the laser wavelength (green vs. blue) changes the pattern significantly.
Changing the laser incidence angle can produce different beam profiles (for example, circular, elliptical, or even square-like patterns).
I tested several other liquids, but they did not produce the same stable and repeatable pattern. This specific mixture consistently does.
I have already discussed this with two photonics professors. Both suggested that the underlying physics is most likely classical thin-film interference/Newton’s rings, which I completely accept. I am not claiming a new physical phenomenon.
My question is different:
Could such a simple glass–liquid system be interesting from an optical engineering perspective (for example, passive beam shaping or sensing), assuming the behavior is genuinely repeatable?
I have attached photographs of the experimental setup and the resulting patterns.
I would appreciate your thoughts.