- what is the physical reasoning behind it
- reference of the paper
changes the refractive index and therefore the relative power partitioning and the losses
Dear Michalis,
thanks for the answer. But do you know the order of the change in the power transmission corresponding to the change in pH values?
Interesting Question !
In literature (e.g. Ring Resonator based sensing application) we find that people have characterized the resonators for different concentrations of salt in DI-water. The results and sensitivities are different for each concentration. Also, using different solutions such as PBS, DI water, KCl, NaCl, etc. (all have different pHs) results in different sensitivity values for such sensors.
As these sensors usually used to monitor bulk refractive index shift, I would say that the pH changes the refractive index of the liquids.
Intuitively, considering the salt dissolved in water at different concentrations gives different pH levels, one could say that with different concentrations, the interactions between salt and water molecules changes and also effects the density of the solution. This would effect the refractive index. I personally think that the effect would be very small of the orders of 1/100 to 1//500 of the value of the refractive index.
Thansk Usman for the answer. to confirm it i will try to do a small experiment soon and see the order of magnitude change. i agree it should not be a big number.
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