title: Retroemission by a glass bead monolayer for high-sensitivity, long-range imaging of upconverting phosphors.
abstract: We introduce a retroemitter (REM) device comprising a planar glass bead set placed on a luminescent material substrate, which converges an excitation beam into a set of foci (voxels). The in-voxel emission is collimated by the beads, and propagates upstream over the long range, unlike the out-of-voxel emission spreading in all angles. The REM signal contrast is characterized as a function of incidence and observation angles and propagation distance. REM signal contrasts of approximately 20 and 1600 were found for the organic fluorescent dye and upconverting phosphor substrates, respectively. In the latter case, nonlinear optical signal enhancement plays a role in addition to the retroemission effect. This allows centimeter-scale REM patterns to be read out at the meter-scale distance using eye-safe sub-mW/cm(2) excitation intensities.
authors.affiliation: MQ Biofocus Research Centre, Macquarie University, NSW 2109, Australia.
authors.forename: Bjørnar
authors.initials: B
authors.lastname: Sandnes
authors.forename: Tim A
authors.initials: TA
authors.lastname: Kelf
authors.forename: Hua
authors.initials: H
authors.lastname: Liu
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Zvyagin
mesh_terms: D005898:Glass / Q000737:chemistry*; D008163:Luminescent Measurements; D008863:Microspheres; D055096:Optical Devices