Compact fluorescence detection system based on self- filtering illumination GaN-based quantum well diodes

The fluorescence detection is one of the most widely used techniques for living cells/tissue imaging and antigens/antibodies recognition in bioresearch and medical diagnosis, determination of specified ions or gas in environmental monitoring , and even strain/ temperature measurement. The III-Nitride MQW LED is an ideal excitation light source for the fluorescence detection system, because it has the advantages of low power consumption, long lifetime, high reliability, compact structure and so on. Here, we report a compact fluorescence detection system based on monolithic DBR-integrated III-Nitride LED chip and demonstrate its application for fluorescence sensor. The applications of the proposed detection system for fluorescence sensor and imaging have been successfully demonstrated. The traditional discrete light source and filter are integrated on a single chip for the proposed system, which not only realizes the separation between excitation and fluorescent lights, but also improves the LED light extraction efficiency. The DBR filter directly covers the back of the sapphire substrate of the uniform luminescent LED. As an optical filter, the DBR has specific wavelength selectivity, while its reflected light helps to increase the radiation flux. Most of the excited blue light is reflected by the filter, and the upward propagating fluorescent red light can pass through the filter. Furthermore, the detection system allows for a removable sample unit and the requirement on sample preparation is much lower. The results indicate that the performance of DBR filter based on amorphous dielectric film is excellent. Therefore, our proposed fluorescence imaging system can effectively avoid the interference of excitation light and greatly reduce the total size of the system, which is conducive to portable applications and field tests. In addition, the cost of the detection system can be greatly reduced because the chip level integrated components in the detection system allow mass production.