Glass in Photonics

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Glass in Photonics
by Khanh Kieu
(11/10/2009)
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Outlines
1. Glass Fundamentals

• What is glass?
• How to make glass?
• Types of glass
• Physical properties
• Optical properties

2. Applications

• Fiber optics communication
• Data storage, laser-induced phase transition
• Microcavity
• Near-field optics

3. Fiber lasers and amplifiers
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Glass material of many uses
Brief History Bottles (3500 years)
Windows (2000 years) Telescope Microscope
Lenses (1590 Netherlands) Mirrors(1680
France) Light Bulbs (1926) Float Glass
(Pilkington , 1959) Glass Laser (1960)
Optical Fiber (1970)
Egypt, 1400-1360 B.C.
Telescope Mirror, College of Optical Sciences
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What is glass?
1945 American Society for Testing
Materials Glass is a an inorganic product of
fusion which has cooled to a rigid condition
without crystallization Satisfactory for
glasses most familiar to us windows, containers
But new methods other than cooling a melt were
developed sputtering, sol gels
1976 Glass is an X-ray amorphous material
which exhibits the glass transition, this is
being defined as the phenomenon in which a solid
amorphous phase exhibits with changing
temperature a more or less sudden change in the
derivative thermodynamic properties, such as heat
capacity and expansion coefficient, from
crystal-like to liquid like values.
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Glass structure
Glasses have the mechanical rigidity of crystals,
but the random disordered arrangement of
molecules that characterizes liquids
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How to determine a materials structure?
Crystals well-defined peaks Amorphous a halo is
seen
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Properties of glassy state

• Lack of long range repeatable order,
  non-crystalline
• structure
• Typically produced from the liquid state by
  continuous
• cooling
• Exhibits what is known as the glass transition
• Can be formed from most liquids, provided
  cooling
• rate is sufficiently high

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Thermal behavior of glass
Most materials Viscosity of melt water
(10-2Pas) Cooling melt ? rapid crystallization
Tm

• Glass forming materials
• Melt with considerable higher viscosity
• Significantly less crystallization below Tm
• If crystallization rate is low enough fast
  cooling below Tm w/o crystallization possible
• further cooling viscosity rising to such high
  values that the mechanical properties become
  similar to a solid

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Thermal behavior of glass viscosity
Typical dependence of viscosity of a glass on
temperature
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How to make glass?

• Mix and heat a composition of chemicals to high
  temperature
• Keep the mixture at high temperature for
  chemical reaction
• Quickly reduce the temperature to annealing
  point
• Anneal at moderate temperature to reduce
  internal stresses
• Slowly bring to room temperature

Movie ?
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Types of glass
Typically glass composes of a glass network
former and several glass network modifiers
Classification based on glass network formers

• Silica SiO2
• Fluorides ZrF4, BaF2
• Phosphates P2O5
• Chalcogenides Se, Te

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Optical properties Transmission window
Vibrational phonon absorption edge
Transmission window
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Optical properties Transmission window
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Refractive index
Fused silica 1.46 Soda-Lime glass
1.518 ZBLAN 1.5 Pb-silicate glass 2.5 Fused
quartz 2.126
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Dispersion
Dependence of refractive index on wavelength
Normal dispersion in transparent
window Anomalous dispersion at resonances
Abbe number
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Color and active glass
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Color and active glass
Nd3, Yb3
Er3
Pr3 (491nm,520nm,605nm,695nm)
Tm3, Ho3
Er3, ZBLAN
Bi3
Pr3
3?m
1?m
2?m
1.5?m
0.5?m
Movie ?
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Fiber optics telecommunication
Source telegeography.com
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Fiber optics telecommunication
Daniel Colladon first described this "light
fountain" or "light pipe" in an 1842 article
entitled On the reflections of a ray of light
inside a parabolic liquid stream. This particular
illustration comes from a later article by
Colladon, in 1884
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Fiber optics telecommunication
1. Low loss optical fiber based on fused
silica 2. Compact, low-cost diode lasers
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Fiber optics telecommunication
Predict the loss in optical fiber could be lt
20dB/km Loss was 1000dB/km at that time
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Fiber optics telecommunication
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Data storage
Recording layer is a phase change material from
the group of Chalcogenides glasses Examples
AgInSbTe, GeSbTe, GeBiTe
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Data storage Phase transition kinetics
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Data storage Phase transition kinetics
ns laser amorphization
ns laser crystalization
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Laser modification of glass ceramics
Movie ?
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Microcavity
Source http//www.vahala.caltech.edu/
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Laser fabrication of microsphere
Movie ?
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Laser fabrication of microsphere
Reflector with ultra-narrow reflection bandwidth
Next lecture
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Near-field probe, micropipette
Near-field image of a SWCNT (Prof.
Novotnys group)
Schematic diagram of a NSOM
(Laserfocusworld.com)
Near field fiber tip
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The world smallest laser gyroscope?

• Basic elements
• Micro-ring laser
• Near-field probe
• Fiber taper

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Summary
1. Glass Fundamentals

• What is glass?
• How to make glass?
• Types of glass
• Physical properties
• Optical properties

2. Applications

• Fiber optics communication
• Data storage, laser-induced phase transition
• Microcavity
• Near-field optics

3. Fiber lasers and amplifiers Lecture on this
Thursday