Study Of All Polymer Asymmetric MZI Waveguide Refractive Index Sensor

With the rapid development of optical communication technology,the requirement for communication bandwidth and capacity has increased dramatically.In traditional circuit,the transmission and switching speed of electrical signals are limited.For photonic integrated circuit(PIC),the active optical devices,passive optical devices and electronic components are integrated in a chip to achieve the signal switching,amplification and sensing.Compared with the transmission of traditional circuit,the high-speed communication among the electronic devices through the optical waveguide has the advantages of large information capacity and high communication speed,and enhances the overall performance of the circuit.Photonic integrated circuits are the developing trend of the interconnection between optical communication and integrated circuit.Optical waveguide sensor is an important optical device of photonic integrated circuit,it has the advantages of high sensitivity,simple structure,anti-electromagnetic interference and multi-channel synchronous detection,etc.The optical waveguide sensor is usually based on the inorganic substrate.Organic polymer materials have the advantage of low cost,while the sensitivity of traditional optical waveguide sensor based on organic substrate is not high.In this paper,the structure of MZI(MachZehnder Interferometer)waveguide device is studied,and an all polymer optical waveguide sensor with high sensitivity,simple process and low cost is designed and prepared.The waveguide of the sensor has three sensing surfaces contact with the test media.Compared with the rectangular waveguide with one sensing surface,inverted ridge waveguide,rectangular waveguide with three sensing surfaces is proved to have higher sensing accuracy and the sensitivity increases by a factor of 5.50,5.24 in theories.Based on rectangular waveguide with three sensing surfaces,asymmetric MZI device structure is designed.When length deviation is 19.8?m and refractive index range is 1.470-1.545,the sensitivity is maximum.We fabricate the asymmetric MZI sensor by lithography and wet etching method.The packaging of the sensor is accomplished using PMMA film.The insertion loss and sensing performance of the sensor are measured using the mixture of benzaldehyde and ethanol.The sensitivity is 791.0d B/RIU and the detection resolution is 1.26×10-6RIU.Besides,the symmetrical MZI and asymmetric MZI polymer sensor structures are optimized theoretically,which improves the sensitivity to more than 1200 d B/RIU.