Semiconductor quantum dots can generate on demand non-classical states of light, a crucial resource for quantum cryptography, photonic quantum simulation and computing. In this context, it is generally desirable to funnel the dot emission into a controlled optical beam, preferentially Gaussian. Since the dot features sub-wavelength dimensions and is surrounded by a matrix with a large refractive index, this represents a significant challenge.

In collaboration with Danish researchers, we have recently proposed a new type of optical antenna to solve this issue: the photonic trumpet. The antenna, which looks like an inverted cone, offers a unique combination of efficient light extraction, clean Gaussian far-field emission and broad operation bandwidth. Through the demonstration of an ultra bright single-photon source based on this strategy, we first evidence the feasibility of these new, high aspect ratio semiconductor structures (the trumpet is 12 µm high and its bottom and top part respectively feature a diameter of 200 nm and 1.6 µm). Furthermore, the device offers appealing performances, with a state-of-the-art light extraction efficiency and the emission of a clean Gaussian beam.

In the future, this strategy could be applied to a wide range of material systems, including nitrogen-vacancy centers in diamond. Thanks to their broad operation bandwidth, photonic trumpets are also very promising for multicolor quantum optics experiments.