An electric field detector using electro-optic device

The fabrication of an electric field detector using electro-optic LiNbO3 (LN) single crystal has been studied for the application to check the electric field of a conductively patterned panel. When this electric field detector moves on the surface of the panel, air gap which is close enough for the given field intensity and resolution has to be maintained constantly not to damage the patterns on the surface. For the effective detection of electric field change in this air gap state, LN single crystal was selected because of the relatively high electro-optic coefficient, transmittance and low dielectric constant. X-cut LN and Z-cut LN structures were selected to estimate the applicability of LN single crystal by the simulation on the optical intensity variation and electric field distribution of the various structures. As the air gap was increased from 0 to 40 (mum) in the X-cut LN structure, half-wave voltage (V-pi) was increased from 400 to 700 (V) and optical intensity variation with unit voltage (Q) was decreased from 1.3 to 0.17. At the air gap of 10mum in the Z-cut LN structure, V-pi was about 100similar to150 (V) and Q was 6.7 (%/V) much larger than that of the X-cut LN structure. From these characteristics, Z-cut LN structure proved to be applicable for the electric field detector because the optical intensity variation (0.8muW) was sufficient in the ac driving voltage region (+/-20V) of the real system.