EDUCATION > Projects > E-field optical sensor

E-field optical sensor

Angular orientation effects on electric field optical sensor

Project Lead

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Assoc. Prof. Dr. Eng. Amir R. Ali 

Executive Deputy

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Eng. Malek Mahmoud 

Project Members

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Eng. M.Sc. Mohamed Ashraf (2017)

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Eng. Momen Algouhary, M.Sc. Student (2019)

Brief description for the project:

In the present project, we are demonstrating the capability of making polydimethylsiloxane (PDMS) microsphere sensors, which take advantage of an optical phenomenon called whispering gallery modes (WGM), a resonance condition happened when the optical path length of a laser in a polymeric microsphere is equal to an integer number of wavelengths, to make extraordinary electric field sensors capable of detecting electric fields. These sensors work by measuring the wavelength at which interference due to WGM occurs and then detecting when this value changes due to a change in the morphology of the spheres. This is possible since PDMS microspheres can be made to physically react to external electric fields. This physical reaction is called the electrostriction effect and governed by Navier’s equation for linear elasticity for steady state case. In this paper, an experiment will be conducted to find the angular orientation effects of the electric field on WGM optical sensors. In this experiment, the electric field is supplied by means of brass plates. These plates are mounted on a servo motor to provide the orientation angle of the applied electric field. The microsphere is placed between the plates. Prior to the experiment, the spheres are subjected to a high strength polling electric field of 1 MV/m. Initial results suggests that the sensitivity of the sphere has a dependence on the angular orientation of the sphere in the sensitizing polling electric field with respect to the orientation in the test electric field. This work we will show a definite relationship between the angular orientation in the sensitizing polling electric field and the response in the test electric field in order to maximize sensitivity. This has direct implications on eventual applications, since the orientation of a future sensor package will directly impact the sensitivity and performance of such a sensor used in the
neurophotonics applications.

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Challenges of the project:

In this project, the effect of the angular orientation of the electric field on the WGM shifts of a PDMS sphere was shown. The applied electric field induces surface pressure forces on the PDMS sphere. In turns, WGM shifts occur in the transmission spectrum of the sphere. Three angular orientations of the test electric field were investigated. Three different orientations are discussed: the normal (θ = π / 2), inclined (θ = π / 4) and parallel (θ = 0) orientations. Typically a polling process was used to charge the sphere with 1MV/m. The results show that, the sphere sensitivity and resolution could be affected by the angle made between the electric field and the optical path that circumnavigate through the cavity. That is due to the surface charge when we polled the cavity under a static electric field with 1MV/m. This surface charge will induce a body force at θ = π / 2 higher than any other orientations leads to higher resolution.