Integrated colloidal quantum dot photodetectors with color-tunable plasmonic nanofocusing lenses

A small, sensitive photodetector that combines a plasmonic lens with a colloidal quantum-dot active area has been made by a team in Spain. Silke Diedenhofen and co-workers from the Institute of Photonic Sciences in Barcelona integrated a flat bull’s eye structure plasmonic lens consisting of a series of corrugated concentric gold rings on a SiO2–Si substrate with an infrared detector made from colloidal PbS quantum dots. The plasmonic lens concentrates and focuses light onto the detector, resulting in a device that has a nanoscale footprint and enhanced sensitivity. The researchers say that they can control and shift the peak wavelength response of the detector within the visible and infrared regions by varying the geometry of the pitch, depth and width of the lens’ rings.