Laser-induced composition change tunes emission energy of nanowire quantum dots

A laser-based technique can tune the energy of a photon emitted from a quantum dot embedded in a nanowire. The ability to fine-tune the properties of a photon produced by a specific quantum dot is an important step toward producing an array that can generate signals for quantum encryption or communication.

Quantum communication networks aim to transmit information using single photons, produced by different sources, that have identical properties such as lifetime, emission energy, polarization, and location. Those identical properties permit interference of the photons to generate entangled photon pairs to carry and transmit information between distant locations. Quantum dots made from semiconductors reliably produce single photons when excited by laser light, but variations in the emission energy between dots make it hard to produce identical photons from different dots.

Tuning the emission of two different dots is discussed in existing literature through the use of applied strain or an electric field. Now Fiset-Cyr et al. describe a technique to tune dots through intermixing, changing their composition using a laser.

By shining a laser on an InAsP quantum dot embedded in a InP nanowire covered with alumina, heat is generated during light absorption. This increases the temperature of the dot enough to allow arsenic to diffuse out of the dot and for phosphorous to diffuse into it. That composition change shifts the emission energy as much as 15 meV, depending on how long it is irradiated by the laser.

Source: “In-situ tuning of individual position-controlled nanowire quantum dots via laser-induced intermixing,” by Alexis Fiset-Cyr, Dan Dalacu, Sofiane Haffouz, Philip J. Poole, Jean Lapointe, Geof C. Aers, and Robin L. Williams, Applied Physics Letters (2018). The article can be accessed at https://doi.org/10.1063/1.5040268 .