Marek A. Osinski

Rapid degradation of CdSe/ZnS colloidal quantum dots exposed to gamma irradiation

Effects of Cs137 gamma irradiation on photoluminescent properties of CdSe∕ZnS colloidal quantum dots are reported. Optical degradation is evaluated by tracking the dependence of photoluminescence intensity on irradiation dose. CdSe∕ZnS quantum dots show poor radiation hardness, and severely degrade after less than 20kR exposure to 662keV gamma photons.

Structure-induced asymmetry between counterpropagating modes in three-port couplers

The continuing controversy regarding the validity of assuming different photon lifetimes for counterpropagating modes in whistle-geometry ring resonators has led us to re-examine the commonly held view that coupling coefficients between any two ports in Y-junction couplers (regardless of their symmetry) do not depend on the direction of propagation. Rigorous three-dimensional finite-difference time-domain simulations show that the common assumptions about the operation o three-port couplers are sometimes grossly incorrect, as they arise from an oversimplified analytical model. An explanation is given why our results do not violate the Helmholtz reciprocity principle.