| Fluorescence sensing remains one of the most widely used detection methodologies for miniaturized and total analysis systems (muTAS). Unfortunately, traditional fluorescence sensing systems remain bulky, non-portable and expensive, stifling the application of muTAS in portable diagnostics and medical care. The theme of this research is to capitalize on optoelectronics developed for telecommunications to create an integrated sensing solution. Integrated semiconductor optoelectronic devices can provide a portable, parallel and inexpensive solution for on-chip fluorescence sensing.; Vertical-cavity surface-emitting lasers (VCSELs) operating at 773nm, PIN photodetectors and emission filters are monolithically integrated to form the optoelectronic basis of the integrated fluorescence sensor. These optoelectronic components are placed in a proximity sensing architecture, where the VCSEL is surrounded by a donut photodetector. This is the first work to integrate a laser and photodetector in such close proximity (≈50mum) towards fluorescence sensing. By bringing the optoelectronic components in such close proximity, laser background sources are created that limit the sensor sensitivity. Laser background sources are characterized, and design solutions are proposed and implemented to reduce laser background. With integrated metal optical blocks, the internal optical isolation between the photodetector and laser is greater than 106, which shows that highly sensitive detection is possible despite the close optoelectronic integration. With the metal blocking structures, the dominant source of laser background is due to reflections occurring above the sensor. The sensor is particularly sensitive to these reflections due to sub-optimal performance from the emission filter.; The sensor is integrated with microfluidic channels to test sensor sensitivity. The experimental and theoretical limit of detection of IR-800 dye is determined to be 250nM and 40nM respectively. These detection limits are sufficient for applications such as clinical chemistry and immunology. Large increases in sensor sensitivity are possible through the systematic reduction of laser background and will enable a wider range of applications. Results from this first generation sensor suggest that order of magnitude increases in sensitivity will be possible by improving the filter performance and increasing spatial filtration. It is believed that this technology holds great potential to reach detection limits less than 1nM and compete against bulk optical approaches. |
