Researchers develop efficient method for producing single photon sources

Published on
September 15, 2023

A team of QCS researchers from Cardiff University and the University of Sheffield have developed a new manufacturing process to produce semiconductor light sources, capable of generating high-purity, indistinguishable single photons on demand. These single photon sources are crucial for numerous applications in the rapidly developing field of quantum technology

Micropillar fabrication. (a) Schematic of processing steps (b) Wide area scanning electron microscope image of etched structures with a variety of different diameters (c) SEM of a high Q-factor micropillar of diameter 1.75 μm. Click here to enlarge.

The sources integrate micron-sized ‘micropillar’ cavities and individual quantum dots that emit single photons when excited by a laser, on a chip containing thousands of devices. The cavity design developed by Cardiff enhances photon emission and efficiently guides it into a mode that can be collected and used. Previously, the production of these small, high-precision micropillar cavities required specialized techniques. The new method, however, employs a technique known as direct-write lithography, which allows for the rapid patterning of the cavities onto a semiconductor wafer.

Professor Anthony Bennett, from Cardiff University, who led the research said “We have shown this high-throughput manufacturing technique can produce really high quality cavities. In future, the ability of direct-write lithography to reconfigure designs in a few seconds should allow us to position cavities accurately over each dot, leading to a huge increase in yield”.

Their new technique is presented in the paper Direct-write projection lithography of quantum dot micropillar single photon sources, published in the journal Applied Physics Letters. It allows the team to achieve mass patterning of high-aspect-ratio pillars with vertical, smooth sidewalls maintaining high-quality for diameters below 2.0 μm. They demonstrated that their quantum dots could emit single photons with an indistinguishability of 0.941 ± 0.008. Indistinguishability refers to how identical the photons are in terms of their colour, polarization, waveform, and arrival times. This characteristic is vital for applications such as quantum computing and secure communication, which rely on identical single photons interacting in precise ways.

This advancement in manufacturing could pave the way for mass production of high-quality single photon sources. As quantum technologies evolve from proofs of concept to real-world applications, the availability of scalable, high-quality components will become increasingly important. This research presents a promising new technique that could supply single photon sources for future quantum deployments.

Dr Ian Farrer, who grew the semiconductor material in the National Epitaxy Facility at the University of Sheffield said “It is wonderful to see a first external-user publication from the new DCA dual P700 reactor. This work confirms the high quality of semiconductor quantum light source this custom-built machine is capable of producing”.