The Spectroscopic Study of Cr4+ Doped CaO-GeO2-Li2O-B2O3(Al2O3) 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

Center for Nanoscale Photonics

C

PN

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 ≤ 1m

• Cr doped glass ceramics exhibit a broad band of fluorescence (1000-1600nm wavelength; peaking at 1280nm).

• Optical properties similar to CUNYITE crystals (i.e.,Cr4+: Ca2GeO4 )

• Absorption and Fluorescence Spectra of the samples help better understand the optical properties of glass-ceramics

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

Recipe for Manganese-Doped Calcium Germanium Glass

[2.0 CaO – 1.0 GeO2 – 1.0 Li2O – 0.5 B2O3 – 0.2 (Al2O3) – 0.04 (P2O5)]

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 CarbonateLi2CO3 – Lithium CarbonateGeO2 – Germanium OxideB2O3 – Boron OxideAl2O3 – Aluminum OxideNH4H2PO4 – Ammonium Dihydrogen PhosphateMnCO3 – Manganese (II) Carbonate

Mn-doped Glass Media

Checkpoint

Powders

Liquid

Solid

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

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

• 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

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

450 550 650 750 850 950

Wavelength (nm)

Ab

so

rpti

on

In

ten

sit

y

No heat treatment Abs

8 hours, 501 C Abs

1 Hour, 520 C Abs

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

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

Light Fluorescence

Excited State

Electron

680-nm laser

0.00E+00

1.00E-05

2.00E-05

3.00E-05

4.00E-05

5.00E-05

6.00E-05

800 900 1000 1100 1200 1300 1400 1500 1600

Wavelength (nm)

Flu

ore

sc

en

ce

No heat Treatment

1 Hour in 520 C

8 Hours in 501 C

Maximum of broad band emission

Fluorescence of Cr-Doped Glass Media

Mn-doped Glass Media

20 hours in 495°C45 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

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

300 400 500 600 700 800 900 1000

Wavelength (nm)

Ab

sorp

tio

n I

nte

nsi

ty

No Heat Treatment Abs

45 minutes, 560°C Abs

10 hours, 495°C Abs

45 Minutes in 560°C

10 Hours in 495°C

Absorption of Mn-Doped Glass Media

Fluorescence of Mn-Doped Glass Media

0.00E+00

2.00E-06

4.00E-06

6.00E-06

8.00E-06

1.00E-05

1.20E-05

1.40E-05

1.60E-05

1.80E-05

2.00E-05

525 575 625 675 725 775

Wavelength (nm)

Flu

ore

scen

ce

No Heat Treatment

10 hours, 495°C

45 minutes, 560°C

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

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

Reference

• “Confocal microscopy of colloids” V Prasad, D Semwogerere, ER Weeks, J. Phys.: Cond. Mat. 19, 113102 (2007)

• Synthesis and characterization of Cr4+ -doped CaO-GeO2-LiO-B2O3(Al2O3) 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

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 MoyMr. Jose Lai, Mr. Jorge Franco

Mr. David Deutsch, Ms. Charlene Chan-Lee

Acknowledgements