Coherent mode decomposition of multiple quantum well light emission

Developing a richer understanding of the various properties of light is central to the field of photonics. One often neglected degree of freedom (DOF) is the second-order correlation of the light field, known as coherence. To make proper use of this DOF, one needs to first obtain information about the field's coherence, which may be characterized through the cross spectral density (CSD) function. We present a measurement of the CSD of a ubiquitous, partially coherent source: a multiple quantum well device in its near-field region, where a photonic structure would commonly encounter the emitted field. We show a departure from the coherence area that is expected from an incoherent source and demonstrate the application of coherent mode decomposition as a way to further analyze the measured results.