Polymer Optical Waveguide Biosensor Design And Interrogation

Planar waveguide optical biosensors based on the principle of evanescent wave for sensing,have broad applications,with the advantages of the high sensitivity,easy integration,diverse structures,real-time detection and so on.Among various planar waveguide optical biosensors,polymer waveguide optical biosensors have been attracting much attention due to their easiness for fabrication and good biological compatibility.From the perspective of improving sensitivity,the finite difference beam propagation method is used to simulate polymer waveguide optical biosensors which work at 850 nm.Slot waveguide microring sensor and spectral splitting based MZI waveguide sensor are designed.A kind of phase interrogation method is analyzed and validated.The main works are as follows:The Slot waveguide is adopted to improve the sensitivity with the enhanced interaction between optical field and the biological solution under test.With the condition of single mode transmission,optical polarization state is selected,and the structural parameters of microring waveguide cross section,such as waveguide height,Slot width and single waveguide width,are optimized.In order to improve the coupling efficiency between input/output waveguide and fiber,the ridge waveguide structure is used as straight waveguides.Considering microring loss,free spectral range,quality factor,optical transmission power and extinction ratio,the bend radius and the coupling efficiency of the microring sensor are optimized.The sensitivity of the Slot waveguide microring sensor is double of that of the ridge waveguide microring sensor.Considering the resolution of the detection system,the Slot waveguide microring sensor has a half of the detection limit,compared with the ridge waveguide microring sensor.The spectral splitting principle is applied to improve the sensitivity of the Mach-Zehnder sensors.On the basis of the spectral splitting theory and single mode condition,the widths of the two sensing arms are chosen to increase the phase difference.From the perspective of flexibly adjusting the initial dip wavelength of the interference spectrum and the spectral splitting range,the sensor with two unequal long sensing arms is designed.One arm of the sensor uses straight waveguide,while the other uses bend waveguide,therefore the length difference between the two arms can be adjusted flexibly.To reduce the transmission loss of branch structure,multiple-mode interference waveguide brance structure is designed and optimized.Compared with the Slot waveguide microring sensor,the sensitivity of the waveguide sensor using spectral splitting effect is improved 2~3 orders of magnitude.Considering different lengths of sensing arms,the preparation tolerance of sensing arms and different branch structures,multiple groups are set in the mask design.Then the mask of spectral splitting based MZI sensor is drew through CAD software.And the mask is prepared.A phase interrogation method for the MZI and microring sensors based on radio frequency modulation is analyzed and the related formulas are derived theoretically.With this phase interrogation method,the sensing phase difference can be obtained directly through the second harmonic and third components of detected electrical signal.The validation of the method is verified through the simulation of Matlab software.And the feasibility is experimentally validated.According to the results of simulation and experiment,the detecting precision and dynamic range of this phase interrogation method are analyzed.The cause for the difference between the experiment results and the simulation results is discussed.This work provides the basis for subsequent sensing interrogation experiment.