Wolfgang Elsäßer

Institute of Applied Physics, Darmstadt University of Technology, Darmstadt Germany

Quantum noise of optoelectronic emitters: an excursion from squeezed states of light emitted by VCSELs via the intensity noise of Quantum Cascade lasers to Quantum Dot super-luminescent diodes

Since the advent of laser, there has been always a perpetual and accompanying research on the quantum fluctuations of light. In this contribution I shall give an overview on the intensity noise properties of recent optoelectronic semiconductor-based light emitters. Since the pioneering work of Y. Yamamoto in the 80ies on the possibility of sub-shot noise emission characteristics or Sub-Poissonian statistics of edge-emitting semiconductor lasers there has been always a continuous search for improvements and the optimum emitter structure, both in theory and experiment. In this talk, I would like to concentrate on three examples of emitters to illustrate the idea and the physics behind. Starting with sub-shot noise emission of Vertical-Cavity Surface-Emitting Lasers (VCSELs), the basic concept will be illustrated before moving further on towards quantum cascade lasers emitting in the mid-infrared around 5 to 10 micrometers. Here, emphasis on the newly observed scaling behavior of the intensity noise will be made, which is due to the particular level-scheme and the cascaded structure, thus requiring a different rate equation description in comparison to edge emitters. Finally, the intensity noise behavior of near-infrared emitting quantum-dot gain medium super luminescent diodes (SLDs) will be studied. It exhibits the typical excess noise behavior due to the amplified spontaneous emission process. Finally, a comparison and a conclusion will be drawn, both, under the aspect of quantum optics and applications of these optoelectronic emitters, as e.g. in high-resolution spectroscopy or optical coherence tomography.

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