Spatial cross section of local and non-local upconversion processes for   upconversion in InAs based quantum structures
  Transients of upconverted photoluminescence (UPL) from molecular beam epitaxy (MBE) grown InAs quantum structures have been obtained. The results indicate the importance of spatial energy transfer cross section in the upconversion processes. The time constants determined suggest that several monolayer (ML) thick InAs quantum structures are the origin of upconversion. Both the time resolved and continuous wave data allow for the discussion of the dynamic balance between a local process (for example excitonic Auger process) and non-local process (for example two-step two-photon-absorption process with photon recycling) in such a system. 
David M. Tex and Itaru Kamiya
cond-mat.mes-hall physics.optics