Research On Biodetectors Based On Organic Photonic Crystal Logic Devices

The economic development and technological progress have brought many conveniences to human beings.However,they have also caused certain negative effects on the living environment.Most of the substances that cause the negative effects are generally trace amounts.In environmental management and protection,we need to perform qualitative or quantitative detection of these trace substances,so it is necessary to develop a sensitive,accurate and easy-to-read biological detection device.Research has shown that when electrodes modified with bioprobes such as photosynthetic bacterial secretions contact with the test solution,the electrical signals in the process of biorecognition are collected and amplified by the probes to form bioelectrical signals which can be identified and measured.In addition,organic semiconductor materials have strong electro-optical effects.Therefore,in this thesis,we designed organic photonic crystals(PhCs)as a platform to detect the concentration of sulfur ions generated by in-situ induced photosynthetic bacterial secretions based on the bioelectrical signals loaded on a PhC waveguide and the Pockels electro-optical effect of organic semiconductors.By the interference of transmission signals through multiple waveguides,we achieved various forms of logical function which provides a fast and efficient detection method for the bioelectricity measurement.Based on the logic function of organic PhCs,the biodetector includes an electrode modified by a biological probe,an electric signal amplification device,an organic PhC logic device,and a signal detection device.We first designed a 2×2 channel organic PhC optical switch that can be applied to detect sulfur ion concentration.The device operates at the wavelength of 1.55 μm.We analyze the influence of the path refractive index change and the electro-optic coefficient on the output performance,determine the basic parameters of the PhC structure,and optimize the PhC waveguide.Furthermore,we load bioelectrical signals on an input waveguide end which are induced by different sulfur ion concentrations and achieve beam interference in the multimode interference(MMI)region based on the waveguide coupling effect,self-image effect,and Pockels electro-optic effect.Research shows the switching device has the transmission efficiency up to 80%and the switching contrast of 8.71 dB.Following,we designed a 2×3 channel organic PhC logic device,and realized logical operation functions such as OR,XOR,and XNOR.The length and width of the multi-mode interference region in this device are 58μm and 6.5μm,respectively.The overall output efficiency exceeds 70%,and the switching contrast is more than 10 dB.By analyzing the relationship between the working state of the output waveguide and the bioelectric signal,we have realized to monitor the changes in the concentration of sulfur ions.The research results will have reference value and practical significance in the detection of environmental pollutants,as well as improving the detection accuracy and speed,and reducing energy loss.