Measuring radiative current in optically pumped gain media

Introduction - The radiative recombination current is a critical material property of optical gain media, knowledge of which is essential for the design of efficient emitters: it determines the threshold current of a laser and controls the performance of an LED. Fundamentally, it represents the fraction of injected electron-hole pairs that are radiated as spontaneously emitted photons. The radiative current can be derived from edge emitted amplified spontaneous emission (ASE), measured using the variable stripe length (VSL) method, provided the measurement system has been properly calibrated. To date such calibrated measurements have only been carried out using an electrically pumped technique [1]. However characterisation by optical pumping is long established and is inherently more desirable as no fabrication is required to detennine the potential of a material as an optically, or electrically, pumped device. Furthermore, for new laser and LED materials such as organic and colloidal dot emitters that cannot be contacted electrically, characterization with an optically pumped technique is the only option. In this work we introduce an experimental methodology for optically pumped media that enables measurement of the radiative recombination current in real units.