title: Micron scale directional coupler as a transducer for biochemical sensing.
abstract: A microfabricated directional coupler (DC) was used for the detection of DNA conjugated with quantum dots. Output optical signals from DCs of a wide range of device lengths correspond well to theoretical and simulation results. Even 20 µm-long DC devices could detect changes in the output optical intensity by monitoring the near-field pattern using a CCD camera. The signal was enhanced 60 × using a 1500 µm-long DC device. For large cladding refractive-index changes between air and water, the normalized signal changed cyclically several times between 0 and 1. The results suggest that the DC can be the basis for miniaturized two-dimensionally integrated biochemical sensors.
authors.forename: K
authors.initials: K
authors.lastname: Uchiyamada
authors.forename: K
authors.initials: K
authors.lastname: Okubo
authors.forename: M
authors.initials: M
authors.lastname: Yokokawa
authors.forename: E T
authors.initials: ET
authors.lastname: Carlen
authors.forename: K
authors.initials: K
authors.lastname: Asakawa
authors.forename: H
authors.initials: H
authors.lastname: Suzuki