Semiconductor rydberg physics

This topical review addresses how semiconductor systems may reveal scalable properties similar to those known from Rydberg atoms and in which ways they may be utilized for precision sensing and to realize huge long-range interactions in semiconductor systems. Due to the interdisciplinary nature of the field, it has a twofold purpose: First, it may serve as an introduction to Rydberg physics for semiconductor physicists unfamiliar with the topic. Second, it may also serve as an overview of the specific opportunities and challenges arising in semiconductor physics for researchers who are familiar with Rydberg physics of cold atom gases, but new to the field of semiconductor physics. The review starts with an introduction on the general properties of excitons in semiconductors. Then, the material system Cu2O, which is the best developed platform for semiconductor Rydberg physics at the moment, is discussed in detail

Distinguishing intrinsic photon correlations from external noise with frequency-resolved homodyne detection

In this work, we apply homodyne detection to investigate the frequency-resolved photon statistics of a cw light field emitted by a driven-dissipative semiconductor system in real time. We demonstrate that studying the frequency dependence of the photon number noise allows us to distinguish intrinsic noise properties of the emitter from external noise sources such as mechanical noise while maintaining a sub-picosecond temporal resolution. We further show that performing postselection on the recorded data opens up the possibility to study rare events in the dynamics of the emitter. By doing so, we demonstrate that in rare instances, additional external noise may actually result in reduced photon number noise in the emission

Photon Statistics of Semiconductor Light Sources

In recent years, semiconductor light sources have become more and more interesting in terms of applications due to their high efficiency and low cost. Advanced designs like lasing without inversion make it possible to approach the ideal so-called thresholdless laser. However, the drawback of such highly efficient light source lies in the rather complicated techniques needed to characterize the emission properties. While common laser emission above and below the lasing threshold can easily be distinguished just by analyzing the output power, the more sophisticated technique of characterizing the emission in terms of their coherence properties by Hanbury Brown-Twiss interferometry must be applied to characterize semiconductor lasers. This poses several problems. Coherence properties manifest in the emission photon statistics, but only on timescales shorter than the coherence time of the emission. While typical coherence times are still in the nanosecond range for common lasers operated below threshold, they are as short as a few tens of picoseconds for semiconductor lasers. This poses a problem as the most commonly used detectors to measure photon statistics are photodiodes which offer a temporal resolution of hundreds of picoseconds at best. This work discusses an alternative experimental approach to measure photon statistics using a streak camera. The best possible time resolution using this setup is shown to be on the order of two picoseconds and therefore sufficient for measurements on semiconductor lasers. This experimental technique is applied to several kinds of semiconductor-based light sources, including quantum-dot vertical-cavity surface-emitting lasers, planar microcavity lasers and so called polariton-condensates. The thresholds of these devices are identified by analysis of the emission photon number statistics and a transition from thermal light towards coherent emission is evidenced. Also, unexpected features like antibunching from a quantum dot ensemble or scattering between the condensate ground state and its excitation spectrum are discussed

Adiabatic Control of Spin-Wave Propagation using Magnetisation Gradients

Spin waves are of large interest as data carriers for future logic devices. However, due to the strong anisotropic dispersion relation of dipolar spin-waves in in-plane magnetised films the realisation of two-dimensional information transport remains a challenge. Bending of the energy flow is prohibited since energy and momentum of spin waves cannot be conserved while changing the direction of wave propagation. Thus, non-linear or non-stationary mechanisms are usually employed. Here, we propose to use reconfigurable laser-induced magnetisation gradients to break the system's translational symmetry. The resulting changes in the magnetisation shift the dispersion relations locally and allow for operating with different spin-wave modes at the same frequency. Spin-wave momentum is first transformed via refraction at the edge of the magnetisation gradient region and then adiabatically modified inside it. Along these lines the spin-wave propagation direction can be controlled in a broad frequency range with high efficiency

Nonlinear spectroscopy of exciton-polaritons in a GaAs-based microcavity

We present a systematic investigation of two-photon excitation processes in a GaAs-based microcavity in the strong-coupling regime. We observe second harmonic generation resonant to the upper and lower polariton level, which exhibits a strong dependence on the photonic fraction of the corresponding polariton. In addition we have performed two-photon excitation spectroscopy to identify $2p$ exciton states which are crucial for the operation as a terahertz lasing device, which was suggested recently [A. V. Kavokin et al., Phys. Rev. Lett. \textbf{108}, 197401 (2012)]. However, no distinct signatures of a $2p$ exciton state could be identified, which indicates a low two-photon pumping efficiency

Quantum-Optically Enhanced STORM (QUEST) for Multi-Emitter Localization

Super-resolution imaging has introduced new capabilities to investigate processes at the nanometer scale by optical means. However, most super-resolution techniques require either sparse excitation of few emitters or analysis of high-order cumulants in order to identify several emitters in close vicinity. Here, we present an approach that draws upon methods from quantum optics to perform localization super-resolution imaging of densely packed emitters and determine their number automatically: Quantum-optically enhanced STORM (QUEST). By exploiting normalized photon correlations, we predict a localization precision below 30 nm or better even for closely spaced emitter up to a density of 125 emitters per μm at photon emission rates of 105 photons per second and emitter. Our technique does not require complex experimental arrangements and relies solely on spatially resolved time streams of photons and subsequent data analysis