Electric field sensing and polarisation measurement using advanced multi-pass interrogation type fiber-optic beam deflection probe

Abstract

We present an experimental demonstration of precise determination of electric field and polarisation properties of the sample using fiber-optic beam deflection transducer. We use a cantilever-deflection fiber probe formed by coating an optimized composition of cobalt-modified bismuth ferrite nanocomposite over a selected length at the tip of deflecting fiber to sense the surrounding electric field. In a chronological development through designing and investigating a series of experiments, we establish a configuration exhibiting a high-performance electric field sensing scheme. First, we devise a Sagnac loop assisted beam deflection assembly that doubly modulates light with the varying electric field. The observed results of the sensor are theoretically modeled using the associated parameters, and the polarisation properties of the probe sample are fairly determined. To deploy a multi-pass signal circulation through the probe for enhanced sensitivity, we then conceive of a promising ring resonator design and tested. Next, incorporating the beam-deflection probe in the resonator circuit, we test and optimize the performance of the transducer. The signal modulation in the resonator cavity caused by electric field-induced deflection of fiber is then accurately analysed to understand its response and interpret the variety of experimental results. We demonstrate a high-performance electric field sensor that operates precisely in the 0–0.75 kV/cm range. The polarisation properties of the probe sample for the low field range of 0–0.8 kV/cm are also determined. The method is all-optical and safe for deployment in any hazardous environment. Also, it enjoys all the advantages of optical fiber-based instrumentation and can be suitably adapted to explore higher-order design for applications based on electric field sensing.