Narrow optical linewidths and spin pumping on charge-tunable close-to-surface self-assembled quantum dots in an ultrathin diode

Abstract

We demonstrate full charge control, narrow optical linewidths, and optical spin pumping on single selfassembled InGaAs quantum dots embedded in a 162.5-nm-thin diode structure. The quantum dots are just 88 nm from the top GaAs surface. We design and realize a p-i-n-i-n diode that allows single-electron charging of the quantum dots at close-to-zero applied bias. In operation, the current flow through the device is extremely small resulting in low noise. In resonance fluorescence, we measure optical linewidths below 2 μeV, just a factor of 2 above the transform limit. Clear optical spin pumping is observed in a magnetic field of 0.5 T in the Faraday geometry. We present this design as ideal for securing the advantages of self-assembled quantum dots-highly coherent single-photon generation, ultrafast optical spin manipulation-in the thin diodes required in quantum nanophotonics and nanophononics applications.

Electrical and optical control of single spins integrated in scalable semiconductor devices

“…This use of charge depletion for creating spectrally narrow optical interfaces ( Fig. 3D) could be widely applicable to other experiments in SiC, or to other solid-state emitters such as quantum dots (49,50). Indeed, by applying the same techniques developed here to intrinsic SiC materials, lines as narrow as ~21 MHz are observed (40).…”

Self‐Assembled InAs/GaAs Coupled Quantum Dots for Photonic Quantum Technologies

“…However, this large electric field dependence also results in indirect states which are highly sensitive to charge fluctuations. Techniques such as reducing the amount of current flowing through a single QD, or using optical pumping to overpopulate the charges in those states . Similarly, ongoing research into producing indistinguishable photons from single QDs may also provide new techniques that can be employed to mitigate charge fluctuations .…”

“…Spectral diffusion originates from the change of occupancies of the trap states around a QD. Solutions to such a problem include reducing the amount of current flowing through a single QD, or using optical pumping to overpopulate the charges in those states . After presenting an introduction and review of the band structure and single particle states, we will discuss some of the results relevant to overcoming the FSS and spectral inhomogeneities.…”

“…The self‐assembly process results in a natural inhomogeneous distribution of electron and hole energy levels in QDs that result in ensemble excitonic transitions with a FWHM of around 20 meV . Considering the µeV scale of the optical transition linewidths, the odds of finding two QDs with the same optical transition are very small. While it is easy to tune laser sources and/or cavity wavelength to match the unique optical transition energies of a few QD qubits, a useful quantum computer requires thousands if not millions or billions of qubits, which makes individual laser tuning impractical.…”

“…People have demonstrated tuning the energies of optical transitions in QDs and CQDs using temperature, DC electric field, AC electric field, and strain . Tuning via the Stark shift induced by a DC electric field is the most common method employed.…”