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Research in Optical Sciences

Investigation of the Second-order Coherence Properties of Amplified Spontaneous Emission from Superluminescent Diodes

J. Kiethe, Andreas Jechow

Published Jan 1, 2014• 1 citation
Publisher

Abstract

Amplified spontaneous emission from superluminescent diodes shows thermal like photon statistics, which has potential applications in precision metrology. We investigate the influence of operating parameters on the degree of second order coherence of the emission.
DOI
10.1364/hilas.2014.jw2a.59

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Properties of light sources based on amplified spontaneous emission (ASE) are similar to the properties of lasers in many regards. However, even though ASE has been widely studied, its photon statistics have not been settled. There are no reliable theoretical estimates or unambiguous experimental data for the second-order coherence function of photons that characterizes the coherence properties of a light source. Our computer simulation clearly establishes that, independently of pump power, the light produced by ASE is similar to that of a thermal source. This result lays bare the fundamental difference between ASE radiation and laser radiation.
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We analyze the statistics of photons originating from amplified spontaneous emission generated by a quantum dot superluminescent diode.Experimentally detectable emission properties are taken into account by parametrizing the corresponding quantum state as a multimode phase-randomized Gaussian density operator.The validity of this model is proven in two subsequent experiments using fast two-photon-absorption detection observing second-order equal-time and second-order fully time-resolved intensity correlations on femtosecond timescales.In the first experiment, we study the photon statistics when the number of contributing longitudinal modes is systematically reduced by applying well-controlled optical feedback.In a second experiment, we add coherent light from a single-mode laser diode to quantum dot superluminescent diode broadband radiation.Tuning the power ratio, we realize tailored second-order correlations ranging from Gaussian to Poissonian statistics.Both experiments are very well matched by theory, thus giving first insights into the quantum properties of radiation from quantum dot superluminescent diodes.
We demonstrate experimentally that the first- and second-order coherence properties of light emitted by a quantum dot superluminescent diode can be simultaneously tailored by well-controlled optical feedback. Depending on feedback intensity and feedback spectral range we achieve a spectral width Δλ between 120 and 0.26 nm, corresponding to a coherence length in first order in the range between 13 and 5820 μm, while the central second-order coherence degree g((2))(τ=0) is tuned gradually from a thermal value of g((2))(0)~1.8 down to the coherent laser limit of g((2))(0)=1.0. These results are complemented by comprehensive investigations of relative intensity noise, which are in excellent agreement with the observed intensity correlation behavior.