Dispersion Engineered Photonic Biosensor: From a Chip-for-the-Lab to a Lab-on-Chipvon Lennart Jakob Moldenhauer
With the emerging demand for analytical methods in the field of health care, environmental and food analysis, as well as medical diagnostics, the interest in the necessary biosensors is also increasing. However, the requirements on suitable technologies for an extensive use are high. This triggered a downright race for ever lower detection limits and greater sensitivity. Silicon photonics presents itself as a promising technology platform. However, expensive and bulky equipment is required to achieve suitable performances, which has prevented full commercial market adoption to date and further complicates compact integration in the form of a lab-on-chip. In the context of this work a novel concept for overcoming this challenge is presented. The focus is on the avoidance of bulky and expensive devices for analysis of the resonance spectra, such as tunable laser source (TLS) and optical spectrum analyzer (OSA). They are replaced by cascaded ring resonators, which have been dispersion engineered by means of computer simulations and whose resonances can be shifted by integrated electric microheater structures. In addition, the photonic components were manufactured in cost-effective and fully CMOS-process compatible amorphous silicon. The analyte transport was realized using microfluidic channels. With the actual fabrication of a sensor system for a proof-of-principle in mind, the necessary manufacturing processes are explained and the corresponding fabrication steps are developed. The system fabricated in this way was tested and characterized with a specially developed measuring routine. The results show that despite the omission of OSA and TLS, the sensor can determine changes in the refractive index of liquids with high precision. In addition, the sensor is capable of detecting biochemical binding processes in a time-resolved manner and provides comparable values in terms of detection limits and sensitivity with regard to other existing biosensor concepts.