Design of Transmission-Type Refractive Index Sensor, Based on Silica Planar Lightwave Circuit Using Combination of Refractive Angle and Phase Measurements.

Koichi Maru

doi:10.3390/s19194095

Abstract

A transmission-type refractive index sensor, based on planar lightwave circuit (PLC) technology is proposed. In the proposed structure, we introduce a combination of coarse measurements, using the dependence of the angle of refraction and fine measurement, and the dependence of the phase on the refractive index to measure the absolute refractive index precisely, without expensive optical measurement equipment. The theoretical model of the proposed refractive index sensor is derived based on Fourier optics and transfer function to simulate its performance. The simulation results for the use of the 2.5%-Δ silica-based PLC technology indicate that the proposed structure has the potential to achieve a refractive index error of approximately 1 × 10−6 RIU or less when a monitored power deviation of ±0.05 dB is accepted.

Highlights

Refractive index measurements are required in numerous applications, including chemical analysis, biochemistry, and industrial fields
Several techniques for refractive index measurement, including the minimum deviation-based method [1,2], critical angle method [3,4], use of Fabry-Perot interferometers [5], surface plasmon resonance (SPR) [6,7,8], resonance in photonic crystals [9], fiber Bragg gratings [10,11,12], and multimode fibers [13] have been proposed. In most of these methods, expensive optical measurement equipment, such as an optical spectrum analyzer (OSA) is required in addition to a sensing unit, in order to measure the spectrum of the light from the sensing unit
This sensor was based on planar lightwave circuit (PLC) technology [15,16], which is widely used for optical passive devices deployed in optical communication systems

Summary

Introduction

Refractive index measurements are required in numerous applications, including chemical analysis, biochemistry, and industrial fields. Several techniques for refractive index measurement, including the minimum deviation-based method [1,2], critical angle method [3,4], use of Fabry-Perot interferometers [5], surface plasmon resonance (SPR) [6,7,8], resonance in photonic crystals [9], fiber Bragg gratings [10,11,12], and multimode fibers [13] have been proposed In most of these methods, expensive optical measurement equipment, such as an optical spectrum analyzer (OSA) is required in addition to a sensing unit, in order to measure the spectrum of the light from the sensing unit. The previous work was limited to only a preliminary phase and quantitative

Methods

Results

Conclusion