Integration of an Optical Electric Field Sensor in Lithium Niobate on Insulator

Abstract

Sensors are a major component in any experimental set-up. In a high voltage environment, the aspect of safety must be particularly emphasized and the galvanic isolation is often provided by an optical communication link in between the “electric-sensor” and the “detection-unit”. However, the transformation of electrical to optical signals and back can introduce delays and errors. To mitigate this, electric fields were directly measured with an in-house fabricated optical sensor chip, based on lithium niobate. On the one hand we measured locally with electrodes on chip, on the other hand in an external electric field across the sensor. Here, we measured a sensitivity of $\sim $ (8 mV)/(10 kV/cm) on the chip with peak ac field strengths up to 11 kV/cm and $\sim $ (10 mV)/(1 kV/cm) in free space for 2 kV/cm at net frequency of 50 Hz. Hysteresis effects on the sensor were found to be decreased for the free space arrangement. Thus, the fabrication and test procedures work effectively and the electric field measurements showed a good agreement of the performance comparing the on-chip and free space set up. This allows for fast and easy on-chip testing of new resonator based sensors to optimize the geometry and adapt the sensor to its application.

Keywords

• Electric field sensor
• electro-optic effect
• free space measurement
• Mach-Zehnder modulator
• micro-fabrication
• photonic integrated chip