Ion detection with photonic crystal microcavities

We have experimentally demonstrated a cation and anion sensor by using short linear photonic crystal microcavities with an embedded quantum dot active region. The photonic crystal microcavity covered with an ion-selective polymer forms a submicrometer optical detection system sensitive to small changes of perchlorate anion (ClO4-) and calcium cation (Ca2+) concentrations. (c) 2005 Optical Society of America.