Novel Electric Field Sensing Scheme Using Integrated Optics LiNbO3 Unbalanced Mach-Zehnder Interferometers and Optical Delay-Modulation

Electric field sensing schemes, using Lithium Niobate (LiNbO3) electro-optical retarders, are being studied since several years. A birefringent LiNbO3 electro-optic waveguide (BEOW) has been used as an optical retarder and simultaneously as electric field sensor. The optical delay acts as the carrier of the sensed electric field. Themodulated optical delay is transmitted to ameasurement receiver, which is based on a second optical retarder acting as demodulator. The sensed electric field can be detected only when the sensor and demodulator are optically matched. An important issue when using BEOW's is their inherent sensitivity to temperature, which manifests as dc-drift at the output of the sensing-detection process and limits practical applications. Anovel electric field sensing scheme, using LiNbO3 unbalanced Mach-Zehnder interferometers instead of BEOW's is described in this paper. This new scheme contributes to three main aspects related to electro-optic sensing: sensing-detection of electric fields using matched optical delays; proposes a simple technique for linearizing the sensing-detection process and demonstrates a strongly reduction of the dc-drift phenomena. The contributing aspects are novel and are described in this paper. Such features become very attractive for implementing practical electric field sensing schemes using LiNbO3 integrated optics devices.