Directional and enhanced fluorescence emission in a semicircular microchannel with a nanogroove

Metal microchannel-enhanced fluorescence is a promising method in optical biosensing applications, such as single molecule detection. Metal microchannel that exhibits localized surface plasmon resonance play an important role in fluorescence enhancement, and the directed fluorescence emission can enhance the fluorescence collection efficiency and the sensitivity of fluorescence detection. Simultaneous fluorescence enhancement and directional emission in a microchannel is worth exploring. Here, we present a semicircular microchannel with nanogrooves which can realize the enhanced and directional fluorescence emission. The maximum theoretical enhancement ratio is 148, and the experimental factor can also reach 98 times. The enhancement is caused by the surface plasma resonance based on the semicircular channel and the rectangular groove. Fluorescence emission from dye molecules or quantum dots (QDs) deposited on the semicircular channel is enhanced in specific directions, which are determined by the tilt angle of the rectangular groove. Additionally, when the metal material is replaced with silver, the directional enhancement emission effect can also be achieved, indicating that the structure is universal, which is also proved by experimental verification. The structure can also be used as cost-effective substrates for surface-enhanced spectroscopies and refractive index sensing.