Efficient Collection of Light from Colloidal Quantum Dots with a Hybrid Metal–Dielectric Nanoantenna

We introduce a hybrid metal–dielectric nanoantenna consisting of a metallic bullseye nanostructure and a dielectric waveguide layer, for directing the photon emission of embedded colloidal nanocrystal quantum dots. This structure overcomes the intrinsic losses of plasmonic nanoantennas on one hand and is much more scalable than dielectric nanoantennas on the other. The experimental results demonstrate a very low divergence angle beam, allowing a collection efficiency of 30% of the quantum dot emission into a numerical aperture of 0.55. The experimental results are well reproduced by numerical simulations, which predict a maximal collection efficiency larger than 25% directly into a single mode fiber having a numerical aperture of 0.12 without the need for any additional optics. Such hybrid nanoantennas can significantly improve the performance of quantum dot based devices, from displays to single-photon sources

Highly Directional Room-Temperature Single Photon Device

One of the most important challenges in modern quantum optical applications is the demonstration of efficient, scalable, on-chip single photon sources, which can operate at room temperature. In this paper we demonstrate a room-temperature single photon source based on a single colloidal nanocrystal quantum dot positioned inside a circular bulls-eye shaped hybrid metal-dielectric nanoantenna. Experimental results show that 20% of the photons are emitted into a very low numerical aperture (NA < 0.25), a 20-fold improvement over a free-standing quantum dot, and with a probability of more than 70% for a single photon emission. With an NA = 0.65 more than 35% of the single photon emission is collected. The single photon purity is limited only by emission from the metal, an obstacle that can be bypassed with careful design and fabrication. The concept presented here can be extended to many other types of quantum emitters. Such a device paves a promising route for a high purity, high efficiency, on-chip single photon source operating at room temperature

Full Spectral and Angular Characterization of Highly Directional Emission from Nanocrystal Quantum Dots Positioned on Circular Plasmonic Lenses

We design a circular plasmonic lens for collimation of light emission from nanocrystal quantum dots at room temperature in the near IR spectral range. We implement a two-dimensional k-space imaging technique to obtain the full spectral-angular response of the surface plasmon resonance modes of the bare plasmonic lens. This method is also used to map the full spectral-angular emission from nanocrystal quantum dots positioned at the center of the circular plasmonic lens. A narrow directional emitting beam with a divergence angle of only ∼4.5° full width at half-maximum is achieved with a spectrally broad bandwidth of 30 nm. The spectrally resolved k-space imaging method allows us to get a direct comparison between the spectral-angular response of the resonant surface plasmon modes of the lens and the emission pattern of the quantum dots. This comparison gives a clear and detailed picture of the direct role of these resonant surface waves in directing the emission. The directional emission effect agrees well with calculations based on the coupled mode method. These results are a step toward fabricating an efficient room-temperature single photon source based on nanocrystal quantum dots

Highly directional emission and photon beaming from nanocrystal quantum dots embedded in metallic nanoslit arrays

This paper has been withdrawn by the authors.Comment: This paper has been withdrawn by the author