Atomistic dynamics of photoinduced effects in chalcogenide glass
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Atomistic dynamics of photoinduced effects in chalcogenide glass Donghui Zhao and Himanshu Jain Department of Materials Science and Engineering, Lehigh University, PA 18015 Chalcogenide glasses (ChG) are made of Group VI element(s) (S, Se, and Te), often alloyed with Group IV and/or V elements (e.g. As, Sb, Ge etc). They exhibit many unusual, but very useful photoinduced effects. For example, band gap light can change their optical absorption, refractive index, chemical reactivity, and volume. As a result, integrated optical devices, such as waveguides, resonators, and photonic crystals, can be fabricated by direct laser writing and photolithography on the thin films of ChG. In situ X-ray absorption spectroscopy (XAS) is critical for the fundamental understanding of atomistic mechanisms of photosensitivity of these materials. It is found that a photochemical reaction is triggered locally in which the non- equilibrium homopolar bonds (e.g. As-As, S-S) are converted into heteropolar bonds (e.g. As-S). This bond switching process drives the expansion of bond length throughout the network structure of the material. The state-of-the-art time-resolved XAS provides the first-hand information about the atomistic dynamics of photostructural changes Work performed on beamlines X18B and X19A. Quartz glass substrate Laser, cw/pulse d Objective lens n’ n 0 Laser-induced material modification Refractive index: n’>n 0 Photodarkening: α ’ >α 0 Chemical reactivity Volume change Waveguide Moving stage Direct laser writing!! Photoexpansion Photolithography Fresnel lens Chalcogenide glass thin film 100 μm t R R m exp 1 Bond switching Atomistic dynamics: bond expansion A Kovalskiy et al., 2009 K Tanaka et al., 2006 X18B-X19A
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Laser, cw/pulsed. X18B-X19A. Atomistic dynamics of photoinduced effects in chalcogenide glass. Donghui Zhao and Himanshu Jain Department of Materials Science and Engineering, Lehigh University, PA 18015. - PowerPoint PPT Presentation
Transcript of Atomistic dynamics of photoinduced effects in chalcogenide glass
Atomistic dynamics of photoinduced effects in chalcogenide glassDonghui Zhao and Himanshu JainDepartment of Materials Science and Engineering, Lehigh University, PA 18015
Chalcogenide glasses (ChG) are made of Group VI element(s) (S, Se, and Te), often alloyed with Group IV and/or V elements (e.g. As, Sb, Ge etc). They exhibit many unusual, but very useful photoinduced effects. For example, band gap light can change their optical absorption, refractive index, chemical reactivity, and volume. As a result, integrated optical devices, such as waveguides, resonators, and photonic crystals, can be fabricated by direct laser writing and photolithography on the thin films of ChG.
In situ X-ray absorption spectroscopy (XAS) is critical for the fundamental understanding of atomistic mechanisms of photosensitivity of these materials. It is found that a photochemical reaction is triggered locally in which the non-equilibrium homopolar bonds (e.g. As-As, S-S) are converted into heteropolar bonds (e.g. As-S). This bond switching process drives the expansion of bond length throughout the network structure of the material.
The state-of-the-art time-resolved XAS provides the first-hand information about the atomistic dynamics of photostructural changes in ChG. It is found that the bonds expand as an exponential function of laser exposure time.
Work performed on beamlines X18B and X19A.
Quartz glass substrate
Laser, cw/pulsed
Objective lens
n’
n0
Laser-induced material modification
Refractive index: n’>n0 Photodarkening: α’>α0
Chemical reactivityVolume change
Waveguide
Moving stage
Direct laser writing!!
Photoexpansion
Photolithography Fresnel lens
Chalcogenide glass thin film
100 μm
t
RR m exp1
Bond switching Atomistic dynamics: bond expansion
A Kovalskiy et al., 2009
K Tanaka et al., 2006
X18B-X19A
