Hybrid integration of CdS filters with GaN LEDs for biophotonic chips

Hybrid integration of CdS filters, GaN light-emiting diodes (LEDs) and disposable microfluidics can enable the creation of low-cost autonomous biophotonic chips for fluorescence detection. Sensitive fluorescence detection techniques are a significant demand in biological assays. In such applications, the optical filter performs a critical function in separating the fluorescence emission photons from the more-intense excitation light. In comparison with distributed Bragg reflectors (DBRs), which can be used to successfully filter the excitation signal, the fabrication process of thin CdS films is more straightforward and contains greater process latitude. This report demonstrates that a single CdS film of 2.4 μm can accomplish the same function as many layers of a DBR in the optical filter application of fluorescence detection.