# Presentation: 438311

## Synthesis & Study of Fluorescence Properties of Cr-doped LiInSiO4-Ca2SiO4 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 Cr4+ ion
- 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.

## What are LASERs?

- “LASER” is an acronym for _L_ight _A_mplification by _S_timulated _E_mission of _R_adiation
- 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
- At this moment “spontaneous light emission” occurs.  This is called fluorescence.

**Notes:**
All lasers contain an amplifying mediums, energized substances that can increase the intensity of light passing through it
In a solid-state laser, the one used in this project, the amplifying medium is a crystal containing laser ions of transition series elements

## Laser Properties

- _Monochromatic_
- It contains one specific wavelength of light (one color)
- _Coherent_
- Each photon moves in phase                      with each other (organized)
- _Directional_
- A laser light has a highly focused tight beam and is very strong and concentrated

**Notes:**
The light released is monochromatic

## 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
- In my project, the amplifying medium is a crystal containing Cr4+ ions as dopands.
- 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.

## History

- Previous research in this project revealed the optimal amount of CrO2 to be used in an olivine crystallite structure is between 0.5% and 0.1% of the total weight.
- The Cr4+ ion is the desired valence state for Cr because its fluorescence is greater than the Cr3+ ion and also it encompasses a larger range of wavelengths in the near-infrared region we are investigating.

**Notes:**
Last year when I started this project the research revealed...

## Abstract

- 	The goal of my project, now, is to find the best suitable host for the Cr4+ ion by combining the elements calcium, lithium, indium, silicon, and oxygen to achieve the optimal “Host” crystal structure, in particular of LixInxCaySiO4.  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.

**Notes:**
As a continuation of last year’s work...

## Materials

*Materials*

- The following compounds are being studied as host materials:                    indium oxide (In2O3), lithium carbonate (Li2CO3), silicon oxide (SiO3), and calcium oxide (CaO2) with chromium oxide (Cr2O3) as the dopand
- Temperature-Controlled Furnace
- Electronic Scale
- Mortars
- Crucibles
- Round paper
- Fluorescence setup

**Notes:**
flash pictures

## Methods

- 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
- 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.
- Each powder was heated at 1100°C to obtain the Cr4+ ions needed for our crystal synthesis
- Eight different mixtures were made
- The difference between each mixture was how much lithium, indium, and calcium each one contained

## Compounds Used

- Place chart here

## Characterization of Fluorescence

**Notes:**
Clean table and new picture

## Cr4+ Sample Fluorescence Readings after 1100oC 

- Under Construction

**Notes:**
Bold lines, white background, labels, larger font

## Results

- Further analysis required

## Acknowledgements

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

## References

- "The Causes of Color," K. Nassau, Scientific American, Volume 243, Number 4, October1980, pp. 124-154.
- “Introduction in optical properties measurements of laser crystals” & “Introduction in absorption measurements,” A. Bykov.
- Illustrations: http://www.howstuffworks.com
- Source #4
- Source #5
- Source #6
- Source #7

## The End