Dr. Michael Kaniber
Technische Universität München
Walter Schottky Institut

Prof. Dr. Kai Müller
Technische Universität München
Walter Schottky Institut

Prof. Dr. Jelena Vuckovic
Stanford University
Ginzton Laboratory

In this project, we integrate tailored low-dimensional semiconductors into nanoscale metallic systems. Specifically, we will study the light-matter-interaction of individual self-assembled In(Ga)As/GaAs quantum dots in close proximity to the strongly localized electromagnetic field in gold bowtie nanoantennas. Therefore, we will combine molecular beam epitaxy to grow near-surface, low density quantum dots with subsequent electron beam lithography to realize high-quality antennas. Advanced optical spectroscopy is expected to shed light onto the radiative and non-radiative coupling between optically active, mesoscopic quantum emitters and light fields confined to sub-wavelength scale. This will allow us to evaluate the potential of this semiconductor-plasmonic hybrid system for spin physics applications. Moreover, we will exploit the metallic antennas simultaneously as electrical gates, thus, paving the way for integrating nano-photonics and –electronics on the very same chip.

Final report:

The major goal of this project is to engineer the light-matter-interaction between self-assembled InAs/GaAs quantum dots and lithographically defined plasmonic bowtie nanoantennas. Nanoantennas are key to focus light to nanometre-sized optical volumes and, thus, are expected to strongly modify the spontaneous emission dynamics of the coupled quantum dots. To achieve the goals set, we successfully established a collaboration between Technical University of Munich and Stanford University. Specifically, we developed quantum dots with outstanding optical quality, which have enabled us to demonstrate the generation of novel quantum states of light [1]. In particular, we demonstrated that a resonantly driven quantum dot can emit photon pairs when precisely tailoring the excitation conditions. Moreover, using the simulation methods which we developed we proposed a novel architecture for on-chip integrated non-classical light sources [2]. We further realized and studied the proposed dot-nanoantenna structures and demonstrated strong intensity enhancements up to 16× for quantum dots coupled to bowtie nanoantennas, accompanied by experimentally measured Purcell Factors >3.4× [3,4]. Recently, we unambiguously demonstrated the generation of non-classical light by conducting single-photon correlation measurements with measured values of g⁽²⁾ (0)<0.5 [5]. Finally, we fabricated and characterised first electrically contacted nanoplasmonic antennas on semiconductor substrates, which will pave the way towards electrical control of quantum dot emission using the quantum confined Stark effect. Next steps will include the efficient generation of single photons using fully resonant excitation schemes, exploitation of non-linearities enhanced by the strongly localised fields of the antennas and exploration of optical transitions beyond the electric dipole approximation.

References:

[1] “Signatures of two-photon pulses from a quantum two-level system”, K.A. Fischer et al. Nature Physics doi:10.1038/nphys4052 (2017)

[2] “On-Chip Architecture for Self-Homodyned Nonclassical Light”, K.A. Fischer et al. Phys Rev. Applied 7, 044002 (2017)

[3] “Emission redistribution from a quantum dot-bowtie nanoantenna”, A. Regler et al. J. Nanophoton. 10(3), 033509 (2016)

[4] “Monolithically integrated single quantum dots coupled to bowtie nanoantennas”, A. A. Lyamkina et al. Opt. Exp. 24, 28936 (2016)

[5] A. Regler et al. “Non-classical light generation from antenna-coupled quantum dots”, in preparation (2017)