1. The Spectroscopic Study of Cr 4+ Doped CaO- GeO 2 -Li 2 O-B 2 O 3 (Al 2 O 3 ) transparent glass- ceramics Presentation by: Victor Ortiz School: M.S./H.S. 141 David A. Stein Riverdale/Kingsbridge Academy Mentor: Dr. Alexei Bykov, Prof. V. Petricevic IUSL-Physics Department

2. Introduction Study the behavior of Cr-doped Calcium Germanium glass media during synthesis and devitrification (i.e., heat treatment) A number of glass compositions yield transparent glass- ceramics after heat treatment Crystallites ≤ 1  m Cr doped glass ceramics exhibit a broad band of fluorescence (1000-1600nm wavelength; peaking at 1280nm). Optical properties similar to CUNYITE crystals (i.e.,Cr 4+ : Ca 2 GeO 4 ) Absorption and Fluorescence Spectra of the samples help better understand the optical properties of glass-ceramics

3. Long Term Goal To create new materials for optical amplifiers and fiber-lasers to enhance telecommunication systems and remote LIDAR applications Summer Research Objective To find the optimal temperature and time required for mass crystallization of nanoscale crystallites New Methods For Analyzing Crystallites The use of the Confocal Microscope is a new approach to a better view and understanding of the nanoscale crystallites –Cr-doped glass ceramic emits fluorescence in NIR spectrum –Manganese (II) Carbonate emits fluorescence in visible spectrum

4. Recipe for Manganese-Doped Calcium Germanium Glass [2.0 CaO – 1.0 GeO 2 – 1.0 Li 2 O – 0.5 B 2 O 3 – 0.2 (Al 2 O 3 ) – 0.04 (P 2 O 5 )] Weigh the chemicals and mix into a Mortar Place mixture on crucible and heat at 800°C in order to release carbon gas Measure crucible to see if carbon was release from the substance Heat at 1400°C in order for substance to become a liquid Remove liquid from furnace and set into a container to become a solid Re-heat at 400°C in order to release thermal stress CaCO3 – Calcium Carbonate Li2CO3 – Lithium Carbonate GeO2 – Germanium Oxide B2O3 – Boron Oxide Al2O3 – Aluminum Oxide NH4H2PO4 – Ammonium Dihydrogen Phosphate MnCO3 – Manganese (II) Carbonate Mn-doped Glass Media Checkpoint Powders Liquid Solid

5. Experimental Protocol Cut and Polish glass media into 1-mm thick plates Measure Absorption and Fluorescence Heat at low temperature for nucleation Heat at high temperature for growth of crystallizes Re-measure Absorption and Fluorescence

6. Cr-doped Glass Media 8 hour in 501°C No heat treatment 1 hour in 520°C Few crystallites formed A large number of nanoscale crystallites were formed or a few numbers of large size crystallites

7. All Materials absorb radiation in some ranges of the electromagnetic spectrum The term is used to describe the entire range of light radiation (gamma rays to radio waves) The amount of absorption depends of the wavelength, the amount of absorbing material in the radiation path, and absorption of that material at that wavelength

8. The higher the absorption, the more light will scatter on crystallites in glass ceramics. Larger size of crystallites. The lower the absorption, the less light will scatter on crystallites in glass ceramics. Smaller size of crystallites. 1 hour in 520°C 8 hour in 501°C Absorption of Cr-Doped Glass Media

9. Measuring Fluorescence Spectrum Fluorescence spectrum is the amount of electromagnetic radiation the atom emits when it is excited. When electrons in the element are excited, they jump to a higher energy level. Solid mediums tend to absorb light and store it as heat. As the electron falls back down and leave the excited state, light is re-emitted at longer wavelengths with less intensity. Ground State LightFluorescence Excited State Electron 680-nm laser

10. Maximum of broad band emission Fluorescence of Cr-Doped Glass Media

11. Mn-doped Glass Media 20 hours in 495°C 45 minutes in 560°C No heat treatment Crystallites were formed within the glass ceramic, reasons for color changed are still unknown A small number of crystallites have formed, glass ceramic still transparent

12. 45 Minutes in 560°C 10 Hours in 495°C Absorption of Mn-Doped Glass Media

13. Fluorescence of Mn-Doped Glass Media

14. Conclusion Crystallization in glass media varies according to temperature and heat treatment time. Chromium-doped glass ceramics emit fluorescence around wavelengths of 1200-1300nm, similar to CUNYITE crystals. Manganese-doped glass ceramics is expected to have a broad band fluorescence between 550~700nm when excited at 488nm. The change in color is believed to have to occur due to crystallization all inside of the Mn-doped Glass Media. The behavior of this substance is still unsure

15. Future Plan Study optical properties of crystallites with Mn-doped glass media with confocal microscope Compare the crystallites within the Mn-doped media with that of Cr-doped media Decide another metal to doped depending of results Continue running experiments with Cr-doped glass media and any other metal-doped glass material Long term goal is to create a new material for optical amplifiers and fiber-lasers to enhance telecommunication systems

16. Reference “Confocal microscopy of colloids” V Prasad, D Semwogerere, ER Weeks, J. Phys.: Cond. Mat. 19, 113102 (2007) Synthesis and characterization of Cr 4+ -doped CaO-GeO 2 -LiO- B 2 O 3 (Al 2 O 3 ) transparent glass-ceramics by A.B. Bykov, M. Yu Sharonov, V. Petricevic, I. Popov, L.L. Isaacs, J. Steiner, and R.R. Alfano Optical Properties Measurements of Laser Crystals by Dr. A. Bykov Guide for Absorption and Fluorescence Spectroscopy by Mr. G. C. Tang and Prof. R. R. Alfano Spectroscopic study of chromium-doped transparent calcium germanate glass-ceramics by M. Yu. Sharonov, A.B. Bykov, T. Myint, V.Petricevic, R.R Alfano

17. National Aeronautics and Space Administration (NASA) NASA Goddard Space Flight Center (GSFC) NASA Goddard Institute for Space Studies (GISS) NASA New York City Research Initiative (NYCRI) The City College of New York (CCNY) Dr. Alexei Bykov, Prof. V. Petricevic Dr. Frank Scalzo, Dr. Manuel Zevallos, Mr. Daniel Moy Mr. Jose Lai, Mr. Jorge Franco Mr. David Deutsch, Ms. Charlene Chan-Lee Acknowledgements