Nanoscale Cr 4+ Doped Olivine Crystallites Used In Optical Amplifiers and Lasers Presentation by: Victor Ortiz Mentor: Dr. Alexei Bykov Mentor: Dr. Alexei Bykov

Overview Recently, we discovered a number of glass compositions in Cr-doped CaO-GeO 2 -Li 2 O-B 2 O 3 (A1 2 O 3 ) 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 nm wavelength range with a maximum of about 1260 nm, which is similar to Cr 4+ : Ca 2 GeO 4 (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.

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.

Procedures Experimental Equipment 1.Cut and polish glass samples into 1~2 mm thick. 2.Measure absorption and emission spectra in glass samples. 3.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 4.Measure the emission and absorption spectra of glass ceramic samples.

Experimental Equipment Double beam spectrophotometer Furnace OmniLap 2000

Glass Ceramics Example of glass samples No heat treatment 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.

Glass Ceramics continued They look the same and remained transparent. Nanoscale crystals were formed. These glass ceramics are no longer transparent, which mean changes did occur. Crystals larger than 1µm were formed. These glass samples underwent temperatures of 500º and lower These glass samples underwent temperatures of 520º and higher

Absorption Spectrum Source: Guide for Absorption and Fluorescence Spectroscopy by Mr. G. C. Tang and Prof. R. R. Alfano Energy Levels 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.

Absorption Spectrum Continue … Source: Optical Properties Measurements of Laser Crystals by Dr. A. Bykov Double Beam Spectrophotometer Reference beam Sample beam Light Source Detector

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

Emission Spectrum Continue …

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. 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 520°C for 1 hour. While nanoscale crystallites were formed in a glass sample that underwent a heat treatment of 470°C for 6 hours. Many glass samples became less transparent after undergoing heat treatment higher than 500°C. We believe this is because crystallites larger than 1µm were formed. Some glass samples released a high amount of emission around the wavelengths of nm, which is similar to cunyite crystals.

Reference 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