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# How to calculate the switching speed of MZI?

(joined August 2019)
Participant

Hi..

I have designed MZI electro-optic switch. The voltage applied to the electrodes are manually given, but I need to calculate the switching speed of the MZI by applying voltages with different speed. How to calculate the switching speed.?

### Responses (5):

• #56373
Mubarak Ali
Participant

Hi..

I have designed MZI electro-optic switch. The voltage applied to the electrodes are manually given, but I need to calculate the switching speed of the MZI by applying voltages with different speed. How to calculate the switching speed.?

• #56398
Steve Dods
Participant

Switching speed will be limited to the speed of the slowest part of the system. In MZI, the slowest process will probably be the time it takes to charge the electrodes to create the electric field. The electrodes have both resistance and capacitance, and the time constant of the electric circuit will probably be the longest response time.

• #56423
Mubarak Ali
Participant

Hi Steve Dods..

Consider I am having a DC electric field, which can switch its state(either 0 V or 5 V) with the speed of 1 MHz. How can I apply this electric field to MZI electrodes and capture the response. From this I can test how fast the MZI is responding to the external electric field. Obviously the speed of light propagation is higher than the speed of electric field. But, i need to capture the response of MZI for the speed of external electric field. In this regard I need your help..

• #56470
Steve Dods
Participant

In fact, a change in the electric field will propagate from the electrode at the speed of light. (More precisely, at the speed of propagation of radio waves. Material constants have different values in the radio range than at optical frequencies.) The speed of light is 300 mm/ps, and your dimensions are on the order of µm. Therefore the transit time for propagating the change in the electric field is much shorter than ps. I’m sure the time constant of your electrodes will be longer than that!

+1
• #56471
Steve Dods
Participant

Correction: The speed of light is 300 µm/ps.

• #56488
Mubarak Ali
Participant

Thank you Steve…