Extreme multiexciton emission from deterministically assembled single-emitter subwavelength plasmonic patch antennas

Plasmonic antennas: precise alignment for high brightness Finding practical ways to control and enhance the emission from single-photon sources is important for applications in quantum optics spanning from fundamental science to quantum information processing. While plasmonic antennas are a solution, the accurate alignment and coupling of such antennas to single-photon emitters like quantum dots, vacancy-centrenanodiamonds and fluorescent molecules is extremely challenging. Laser etching can help ease the task, allowing a CdSe/CdS core-shell quantum dot to be deterministically placed inside a subwavelength plasmonic patch antenna with 3 nm vertical and 50 m lateral precision. Amit Raj Dhawan and coworkers from Chengdu, China and Paris, France, show that the precise control over the location of the emitter results in an emitter-antenna system with a brightness enhancement of a factor of 70 and a large Purcell factor >72. Coupling nano-emitters to plasmonic antennas is a key milestone for the development of nanoscale quantum light sources. One challenge, however, is the precise nanoscale positioning of the emitter in the structure. Here, we present a laser etching protocol that deterministically positions a single colloidal CdSe/CdS core/shell quantum dot emitter inside a subwavelength plasmonic patch antenna with three-dimensional nanoscale control. By exploiting the properties of metal-insulator-metal structures at the nanoscale, the fabricated single-emitter antenna exhibits a very high-Purcell factor (>72) and a brightness enhancement of a factor of 70. Due to the unprecedented quenching of Auger processes and the strong acceleration of the multiexciton emission, more than 4 photons per pulse can be emitted by a single quantum dot, thus increasing the device yield. Our technology can be applied to a wide range of photonic nanostructures and emitters, paving the way for scalable and reliable fabrication of ultra-compact light sources.