Synthesis & Study of Fluorescence Properties of Cr-doped LiInSiO 4 - Ca 2 SiO 4 Solid State Solutions By: Caesar Pereira (Archbishop Stepinac H.S.) Supervising Scientist: Prof. V. Petricevic (CCNY) Senior Scientist: Dr. A. Bykov (CCNY)

Background The goal of my research is to develop the most effective crystallites for near-infrared optical amplifiers using the Cr 4+ ion The goal of my research is to develop the most effective crystallites for near-infrared optical amplifiers using the Cr 4+ ion This research will aid in the development of new and more effective lasing media. This research will aid in the development of new and more effective lasing media. The results will bring a deeper understanding of the different olivine structures’ optical properties, such as fluorescence. The results will bring a deeper understanding of the different olivine structures’ optical properties, such as fluorescence.

What are LASERs? “LASER” is an acronym for Light Amplification by Stimulated Emission of Radiation “LASER” is an acronym for Light Amplification by Stimulated Emission of Radiation When a laser ion is pumped with energy, its electrons move to a higher energy level When a laser ion is pumped with energy, its electrons move to a higher energy level The electrons after being excited will spontaneously fall back to the ground state The electrons after being excited will spontaneously fall back to the ground state At this moment “spontaneous light emission” occurs. This is called fluorescence. At this moment “spontaneous light emission” occurs. This is called fluorescence.

Laser Properties Monochromatic Monochromatic It contains one specific wavelength of light (one color) It contains one specific wavelength of light (one color) Coherent Coherent Each photon moves in phase with each other (organized) Each photon moves in phase with each other (organized) Directional Directional A laser light has a highly focused tight beam and is very strong and concentrated A laser light has a highly focused tight beam and is very strong and concentrated

Solid-State Lasers Although the amplifying media can be solid, liquid, or gas, we chose to use solid-state media for our research, such as crystals Although the amplifying media can be solid, liquid, or gas, we chose to use solid-state media for our research, such as crystals In my project, the amplifying medium is a crystal containing Cr 4+ ions as dopands. In my project, the amplifying medium is a crystal containing Cr 4+ ions as dopands. The reason crystals are different colors is because the electron configuration of the ion determines what color we perceive. The reason crystals are different colors is because the electron configuration of the ion determines what color we perceive. In our samples the electron configuration of the Cr4+ ion appears to be the color green. In our samples the electron configuration of the Cr4+ ion appears to be the color green.

History Previous research in this project revealed the optimal amount of CrO 2 to be used in an olivine crystallite structure is between 0.5% and 0.1% of the total weight. Previous research in this project revealed the optimal amount of CrO 2 to be used in an olivine crystallite structure is between 0.5% and 0.1% of the total weight. The Cr 4+ ion is the desired valence state for Cr because its fluorescence is greater than the Cr 3+ ion and also it encompasses a larger range of wavelengths in the near- infrared region we are investigating. The Cr 4+ ion is the desired valence state for Cr because its fluorescence is greater than the Cr 3+ ion and also it encompasses a larger range of wavelengths in the near- infrared region we are investigating.

Abstract The goal of my project, now, is to find the best suitable host for the Cr 4+ ion by combining the elements calcium, lithium, indium, silicon, and oxygen to achieve the optimal “Host” crystal structure, in particular of Li x In x Ca y SiO 4. These compounds will be combined in different concentrations to find which mixture gives the desired fluorescence. The crystals obtained from this research will be effective amplifying media for use in optical fiber communications, remote sensing and other photonics applications.

Materials The following compounds are being studied as host materials: indium oxide (In 2 O 3 ), lithium carbonate (Li 2 CO 3 ), silicon oxide (SiO 3 ), and calcium oxide (CaO 2 ) with chromium oxide (Cr 2 O 3 ) as the dopand The following compounds are being studied as host materials: indium oxide (In 2 O 3 ), lithium carbonate (Li 2 CO 3 ), silicon oxide (SiO 3 ), and calcium oxide (CaO 2 ) with chromium oxide (Cr 2 O 3 ) as the dopand Temperature-Controlled Furnace Temperature-Controlled Furnace Electronic Scale Electronic Scale Mortars Mortars Crucibles Crucibles Round paper Round paper Fluorescence setup Fluorescence setup

Methods Before preparing the powders, stoichiometry was used to calculate the weights of each of the compounds Before preparing the powders, stoichiometry was used to calculate the weights of each of the compounds After weighing out each compound carefully on a very precise scale, the compounds were mixed in a mortar After weighing out each compound carefully on a very precise scale, the compounds were mixed in a mortar Ethanol was added to each powder to make it homogeneous (uniform) but later on evaporated out under a fume hood so as not to change the properties of our compounds Ethanol was added to each powder to make it homogeneous (uniform) but later on evaporated out under a fume hood so as not to change the properties of our compounds

Methods (continued) The compounds underwent long periods of heating in the furnace ~24 hours. The compounds underwent long periods of heating in the furnace ~24 hours. Each powder was heated at 1100°C to obtain the Cr 4+ ions needed for our crystal synthesis Each powder was heated at 1100°C to obtain the Cr 4+ ions needed for our crystal synthesis Eight different mixtures were made Eight different mixtures were made The difference between each mixture was how much lithium, indium, and calcium each one contained The difference between each mixture was how much lithium, indium, and calcium each one contained

Compounds Used Place chart here Place chart here

Characterization of Fluorescence

Cr 4+ Sample Fluorescence Readings after 1100ºC Under Construction Under Construction

Results Further analysis required Further analysis required

Acknowledgements Mentors: Dr. Bykov & Prof. Petricevic Mentors: Dr. Bykov & Prof. Petricevic NASA SHARP / NYCRI NASA SHARP / NYCRI NASA COSI & DoD NPC Summer Program NASA COSI & DoD NPC Summer Program City College of New York City College of New York CREST-CMMS CREST-CMMS NYC-MTA NYC-MTA

References "The Causes of Color," K. Nassau, Scientific American, Volume 243, Number 4, October1980, pp "The Causes of Color," K. Nassau, Scientific American, Volume 243, Number 4, October1980, pp “Introduction in optical properties measurements of laser crystals” & “Introduction in absorption measurements,” A. Bykov. “Introduction in optical properties measurements of laser crystals” & “Introduction in absorption measurements,” A. Bykov. Illustrations: Illustrations: Source #4 Source #4 Source #5 Source #5 Source #6 Source #6 Source #7 Source #7

The End