Wideband deep penetration of photon-number fluctuations into the quantum regime in series-coupled light-emitting diodes

Experimental results on the squeezing of photon-number fluctuations of series-coupled LED's driven by a constant-voltage source are presented that illustrate the advantage of series-coupled LED's, namely, a greater squeezing capability than that of a single LED driven through an equivalent series resistor. We discuss the microscopic origin of the deep squeezing on the basis of quantum-mechanical Langevin equations.