Nanoscale Cr4 Doped Olivine Crystallites Used In Optical Amplifiers and Lasers

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Nanoscale Cr4 Doped Olivine Crystallites Used In
Optical Amplifiers and Lasers

• Presentation by Victor Ortiz
• Mentor Dr. Alexei Bykov

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Overview

• Recently, we discovered a number of glass
  compositions in Cr-doped CaO-GeO2-Li2O-B2O3
  (A12O3) system yielding transparent glass
  ceramics after devitrification.
• The size of the crystallites in glass media is
  estimated to be less than 1 µm.
• These glass ceramic samples exhibit broad band of
  emission in 1000-1600 nm wavelength range with a
  maximum of about 1260 nm, which is similar to
  Cr4 Ca2GeO4 (Cunyite) bulk crystals.
• We measured the absorption and emission spectrum
  to help us understand more about the optical
  properties of these crystallites inside the glass
  ceramic samples.
• These glass ceramic samples are expected to be a
  new material for the development of fiber-lasers
  and optical amplifiers.

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Objective

• To make glass ceramics using different heat
  treatment procedures and to study the optical
  properties of nanoscale glass ceramics.
• To find the optimal temperature and time
  required for mass crystallization of nanoscale
  crystallites to occur.
• To control the process of crystallization via
  time and temperature.
• Our long term goal is to create a new material
  for optical amplifiers and fiber-lasers to
  enhance communication systems and informtion
  transformation.

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Procedures
Experimental Equipment

• Cut and polish glass samples into 12 mm thick.
• Measure absorption and emission spectra in glass
  samples.
• Apply heat treatment to the glass samples in a
  muffle furnace.
• Heat the samples at lower temperature for
  nucleation
• Heat the samples at higher temperature to allow
  the growth of crystallites
• Measure the emission and absorption spectra of
  glass ceramic samples.

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Experimental Equipment
Furnace
Double beam spectrophotometer
OmniLap 2000
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Glass Ceramics

• These materials share many properties with both
  glass and more traditional crystalline ceramics.
• It is formed as a glass, and then crystallized
  partly by heat treatment.
• Glass ceramics can be made near transparent for
  crystallites not exceeding 100 nm. These samples
  will be used for radiation in infrared
  wavelengths.

Example of glass samples
No heat treatment
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Glass Ceramics continued

• They look the same and remained transparent.
• Nanoscale crystals were formed.

These glass samples underwent temperatures of
520º and higher
These glass samples underwent temperatures of
500º and lower

• These glass ceramics are no longer transparent,
  which mean changes did occur.
• Crystals larger than 1µm were formed.

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Absorption Spectrum
Absorption spectrum of 5 glass ceramics

• Absorption spectrum shows the fraction of
  incident electromagnetic radiation absorbed by
  material over a range of frequencies.
• Atoms may change states when they absorb
  specific amounts of energy. Atomic states are
  defined by the arrangement of electrons in atomic
  orbital.
• The electrons move to a higher energy level when
  they absorb specific amounts of energy.

Energy Levels
Energy Levels
Source Guide for Absorption and Fluorescence
Spectroscopy by Mr. G. C. Tang and Prof. R. R.
Alfano
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Absorption Spectrum Continue
Light Source
Reference beam
Sample beam
Detector
Double Beam Spectrophotometer
Source Optical Properties Measurements of Laser
Crystals by Dr. A. Bykov
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Emission Spectrum
Emission measurements of 4 glass samples

• Emission 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. As the electrons
  fall back down and leave the excited state, light
  is re-emitted.

• Emission spectrum can be used to determine the
  ability of the material to be used as a laser.
• The Emission spectrum helps us understand more
  about the properties of the crystallites in glass
  ceramics.

Source Guide for Absorption and Fluorescence
Spectroscopy by Mr. G. C. Tang and Prof. R. R.
Alfano
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Emission Spectrum Continue
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Conclusion

• Crystallization occur in glass media during heat
  treatment.
• The size of crystallites varied according to the
  different temperature and time they were exposed
  to.
• The absorption spectrum shows that large
  crystallites were formed in a glass sample that
  underwent heat treatment of 520C for 1 hour.
  While nanoscale crystallites were formed in a
  glass sample that underwent a heat treatment of
  470C for 6 hours.
• Many glass samples became less transparent after
  undergoing heat treatment higher than 500C. We
  believe this is because crystallites larger than
  1µm were formed.
• Some glass samples released a high amount of
  emission around the wavelengths of 1200-1300nm,
  which is similar to cunyite crystals.

Further Research

• Additional studies will be conducted to test the
  effect of other temperature range and time
  exposure on the formation of nanoscale
  crystallites.
• The absorption and emission spectra will
  continue be used to examine the properties of
  nanoscale crystals formed in glass ceramics.
• In the near future, tests will be conducted on
  the applications of glass ceramics in optical
  amplifiers and lasers.

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Reference

• http//www.thefreedictionary.com/
• http//en.wikipedia.org/wiki/Main_Page
• 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

Acknowledgements
Mentor Dr. Alexei Bykov IUSL High School Summer
Program Summer of 2006 N.A.S.A/C.O.S.I NYCRI OF
2006 And all of the staff members at CUNY