Resonant-cavity optoelectronic devices for fluorimetry

Vertical cavity, semiconductor optoelectronic devices have been designed specifically for applications in fluorescence spectroscopy. The devices emit and detect light in a direction normal to their surface and could be readily integrated into lab-on-a-chip formats with extremely close proximity coupling to the analyte. The emission is narrow band and centered at 645 nm, whereas the detection response is broadband extending from 645 to 870 nm. A resonant cavity structure has been used to independently control the emission and detection characteristics, and a comparison is given between structures with a cavity enhancement at either the emission or the detection wavelength. In both cases, an enhancement by a factor of greater than 15 is achieved due to the presence of the optical cavity. In emission, this provides micrometer-scale devices with power levels in the 50-μW range. When the cavity is used to enhance detection, a minimum detection power level of 100 nW is achieved.