Performance of Refractive Index Sensors Based On Directional Couplers in Photonic Crystal Fibers

Abstract

We present a systematic analytic and numerical study of the detection limit of a refractive index sensor employing a directional coupler architecture within a photonic crystal fiber (PCF). The device is based on the coupling between the core mode and a copropagating mode of a satellite waveguide formed by a single hole of the PCF infiltrated by a high-index analyte. Using coupled mode theory as well as full simulations, we investigate the influence of changes in the geometrical parameters of the PCF and the analyte's refractive index on sensor performance, including sensitivity, resonance width, and detection limit. We show that regardless of the details of the sensor's implementation, the smallest detectable refractive index change is inversely proportional to the coupling length and the overlap integral of the satellite mode with the analyte, so that best performance comes at the cost of long analyte infiltration lengths. This is experimentally confirmed in our dip sensor configuration, where the lowest detection limit achievable for realistic implementation is estimated to 7 × 10 −8 refractive index units (RIU) based on realistic signal to noise ratios in a commercially available PCF.

Integrated quantum photonic sensor based on Hong-Ou-Mandel interference

“…Up to the best of our knowledge the best resolution achieved in schemes [42,43] is of the order of 10 −7 RIU per √ Hz, however these use more input power. The advantages of the presented scheme are as follows.…”

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“…Experimental outcomes show the effectiveness of the proposed system and Phase shifts are considered as a performance parameters. A systematic analytic and numerical study has been proposed by Wu et al [21] which includes the detection limit of a refractive index sensor. The proposed study applied coupled mode theory and investigated implementation results where wavelength (nm), Time (T) have been used as performance parameters.…”

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“…Darran et al [11] studied a curvature sensor based on mode-coupling theory of dual-core photonic crystal fiber, meantime the sensor also requires the OSA. A curvature sensor based on twin core fiber coupler is proposed by Yin [12], however, the measuring limit is only up to the 9.3 m À1 .…”