Collaborative Research: MultiPhoton Phosphors Based on Vacuum Ultraviolet Excitation R' S' Meltzer,

1
Collaborative Research Multi-Photon Phosphors
Based on Vacuum Ultraviolet Excitation R. S.
Meltzer, University of Georgia (DMR-0305400)

• Efforts are underway to develop a new generation
  of mercury-free fluorescent lamps with improved
  efficiency. A near unity quantum yield has been
  demonstrated using photon cascade emission (PCE)
  of Gd3 sensitized by VUV excitation of the
  self-trapped exciton (STE) in ScBO3. In PCE an
  ion decays in a sequential two-step decay thereby
  emitting two photons for each photon absorbed
  (quantum splitting). The figure shows the STE
  emission of pure ScPO4(red curve) at 210 nm. In
  Gd-doped ScPO4 (blue curve) the STE emission is
  almost absent in favor of emission from the 6G
  and 6P states of Gd3. The 6G state emits
  sequentially a red (600 nm) and UV(313 nm)
  photon. The total quantum yield is 1 photon out
  for each input photon. While this still lies
  below the desired value of at least 1.5 it
  demonstrates a new route to efficiently populate
  the 6G state of Gd3 for quantum cutting
  application either through PCE or, alternatively,
  a cross relaxation energy transfer scheme.

2
Collaborative Research Multi-Photon Phosphors
Based on Vacuum Ultraviolet Excitation R. S.
Meltzer, University of Georgia (DMR-0305400)

• Two Ph.D. students and two visiting scholars,
  Professor Hyo Jin Seo (Pukyong National
  University, Korea) and Dr. Sergey Feofilov,
  (Ioffe Institute in St. Petersburg, Russia), are
  currently involved with this project. This
  research provides an opportunity for the students
  to gain expertise in phosphor development and to
  acquire the fundamental concepts in the optical
  properties of solids, especially those of rare
  earth doped insulators which form the basis for
  many phosphors. The training includes the gamut
  of techniques involved in vacuum ultraviolet
  (VUV) spectroscopy. Close cooperation in this
  project with scientists at Osram Sylvania allow
  students to understand the interfacing of
  research and development in an industrial
  setting. Collaborating in this project is
  Professor Keszlers group at Oregon State
  University they design and produce the phosphors
  used in this effort. Students at the two
  Universities see first hand the synergy necessary
  to develop new materials.

Mr. Zhou, a Ph.D. graduate student, and Dr.
Feofilov, a visiting scientist, are shown
operating the VUV spectroscopy system.