Doubt regarding the working of EO-MZI

[Dr.Sudip Roy]

I have a doubt regarding the placement of the electrodes, whether it is done in an unsymmetrical way or symmetrical manner (by symmetrical, I mean the placements of the electrodes is equidistant from the arms of the EO-MZI). The MZI which I simulated in the OptiBPM software by following this link:

Mach-Zehnder Interferometer Switch

The placement of the electrodes is done in an unsymmetrical manner as seen in the link. But, whereas in the research paper that I have enclosed, in the implementation of NOR gate section, they have placed electrodes in a symmetrical manner. So, now my first question is: How should the electrodes be placed? In a symmetrical or unsymmetrical manner? and my second question is: If these electrodes are placed symmetrically(as they are equidistant from the arms of the MZI) ( as seen in the Research paper enclosed), then how does the phase change between two optical signals occurs to get constructive and destructive interference?

Please let me know about it at the earliest.

[Steve Dods]

Q: How should the electrodes be placed? In a symmetrical or unsymmetrical manner? A: The link you provide suggests the symmetrical pattern will have the desired function.

and my second question is: If these electrodes are placed symmetrically(as they are equidistant from the arms of the MZI) ( as seen in the Research paper enclosed), then how does the phase change between two optical signals occurs to get constructive and destructive interference? A: In Fig 2 of the paper, electric field is applied to upper and lower waveguides. The field of the upper waveguide is in the opposite direction from the lower waveguide. The EO effect is linear, so applying the external field in the opposite direction has the opposite effect. Therefore the optical phases at the second coupler become different, and destructive interference occurs.

[Steve Dods]

: In Fig 2 of the paper, electric field is applied to upper and lower waveguides. The field of the upper waveguide is in the opposite direction from the lower waveguide. The EO effect is linear, so applying the external field in the opposite direction has the opposite effect. Therefore the optical phases at the second coupler become different, and destructive interference occurs.

[Steve Dods]

The waveguides and electrodes are in a symmetrical pattern,and there is no apparent difference in the optical wave on the upper waveguide compared to the lower one. However, the EO effect is not necessarily the same. There are 3 electrodes, top, middle and bottom. If the top and bottom electrodes are grounded and potential is applied to the middle one, the EO effect on the upper waveguide is the opposite of the EO effect lower waveguide. The effect, both + and -, gets stronger with increasing potential, leading to constructive or destrtuctive interference in the second coupler.

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