Quantum mechanically indistinguishable particles such as photons may show collective behavior. Therefore, an appropriate description of a light field must consider the properties of an assembly of photons instead of independent particles. We have studied multiphoton correlations up to fourth order in the single-mode emission of a semiconductor microcavity in the weak and strong coupling regimes. The counting statistics of single photons were recorded with picosecond time resolution, allowing quantitative measurement of the few-photon bunching inside light pulses. Our results show bunching behavior in the strong coupling case, which vanishes in the weak coupling regime as the cavity starts lasing. In particular, we verify the n factorial prediction for the zero-delay correlation function of n thermal light photons.
"Photon bunching is not limited to the two photon case and the degree of second-order coherence of a light field can be extended to arbitrarily high orders n . Starting with the more general form of g (2) (t, τ ) with the photon number operatorˆn "
[Show abstract][Hide abstract] ABSTRACT: Two-photon excited fluorescence (TPEF) is a standard technique in modern microscopy, but is still affected by photodamage to the probe. It has been proposed that TPEF can be enhanced using entangled photons, but this has proven challenging. Recently, it was shown that some features of entangled photons can be mimicked with thermal light, which finds application in ghost imaging, subwavelength lithography and metrology. Here, we use true thermal light from a superluminescent diode to demonstrate TPEF that is enhanced compared to coherent light, using two common fluorophores and luminescent quantum dots, which suit applications in imaging and microscopy. We find that the TPEF rate is directly proportional to the measured degree of second-order coherence, as predicted by theory. Our results show that photon bunching in thermal light can be exploited in two-photon microscopy, with the photon statistic providing a new degree of freedom.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate a new approach to measuring high-order temporal coherences that uses a four-element superconducting nanowire single-photon detector. The four independent, interleaved single-photon-sensitive elements parse a single spatial mode of an optical beam over dimensions smaller than the minimum diffraction-limited spot size. Integrating this device with four-channel time-tagging electronics to generate multi-start, multi-stop histograms enables measurement of temporal coherences up to fourth order for a continuous range of all associated time delays. We observe high-order photon bunching from a chaotic, pseudo-thermal light source, measuring maximum third- and fourth-order coherence values of 5.87 +/- 0.17 and 23.1 +/- 1.8, respectively, in agreement with the theoretically predicted values of 3! = 6 and 4! = 24. Laser light, by contrast, is confirmed to have coherence values of approximately 1 for second, third and fourth orders at all time delays.
[Show abstract][Hide abstract] ABSTRACT: This topical review provides an overview of quantum dot micropillars and their application in cavity quantum electrodynamics (cQED) experiments. The development of quantum dot micropillars is motivated by the study of fundamental cQED effects in solid state and their exploitation in novel light sources. In general, light-matter interaction occurs when the dipole of an emitter couples to the ambient light field. The corresponding coupling strength is strongly enhanced in the framework of cQED when the emitter is located inside a low mode volume microcavity providing three-dimensional photon confinement on a length scale of the photon wavelength. In addition, coherent coupling between light and matter, which is essential for applications in quantum information processing, can be achieved when dissipative losses, predominantly due to photon leakage out of the cavity, are strongly reduced. In this paper, we will demonstrate that high-quality, low mode volume quantum dot micropillars represent an excellent system for the observation of cQED effects. In the first part the fabrication and the technological aspects of quantum dot micropillars will be discussed with a focus on the AlGaAs material system. The discussion involves the epitaxial growth and the processing of optically as well as electrically driven micropillar structures. Moreover, micropillars realized in alternative material systems and other resonator geometries will be addressed briefly. The second part will focus on the optical characterization of micropillar cavities with respect to their mode structure and the quality (Q) factor for different device geometries and resonator layouts. In the final part, we will present cQED experiments with quantum dot micropillars. Here, weak and strong coupling effects in the framework of cQED will be presented. These effects are strongly related to possible applications of quantum dot micropillars, such as single photon sources and low threshold microlasers, which will also be discussed. The paper will close with an outlook on current and future developments and a summary.
Journal of Physics D Applied Physics 01/2010; 43(3). DOI:10.1088/0022-3727/43/3/033001 · 2.72 Impact Factor
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