Determination of 1'5m fluorescence lifetime in erbiumdoped glass using laserexcited fluorescence

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Determination of 1.5??m fluorescence lifetime in
erbium-doped glass using laser-excited
fluorescence

• Peter Bowyer
• School of Physics and Astronomy
• University of Southampton
• Highfield
• SO17 3JH

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Outline

• Introduction
• Why laser-excited fluorescence
• Introduction to the theory
• Experimental setup
• Experimental results
• Analysis
• Errors Conclusion

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Introduction

• Why laser-excited fluorescence?
• Widely used in telecommunications industry for
  amplification of optical signals
• When a weak optical signal passes through
  erbium-doped glass it stimulates the excited Er3
  ions to emit radiation of the same wavelength,
  amplifying the input signal
• Why Erbium?
• 4f shell incomplete and screening by outer 5s and
  5p shells
• Leads to some metastable states which emit at
  correct wavelength
• Why measure the decay time?
• The longer the lifetime, the more efficient the
  device more suited for use in an amplifier

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How fluorescence occurs
4F9/2
Excited states decay radiatively or vibrationally
to metastable state
4I9/2
4I11/2
4I13/2
Electrons in Er3 ions excited using input laser
Decays to ground state, fluorescing (1.55 ?m)
4I15/2
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Glass samples
Sample A Erbium-doped fluorozirconate glass
(ZBLAN) Soft glass, ionically bonded 2 erbium
fluoride
Peter Bowyer Sample A has more radiative decay
as loads of metastable states Sample B is with
tougher bonds more vibrational decay possible
Sample B Lead germanate glass relatively hard
oxide glass, covalent bonding 0.1 Er2O3
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Experimental setup

• Schematic diagram of equipment

Peter Bowyer Laser is square-wave
pulsedcharges crystal, which decays when laser
not on
Final measurements performed in darkroom
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Experimental Results
Sample B
Sample A
1 vertical square 500mV
1 vertical square 200mV
Horizontal time scale is identical (10ms per
square)
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Analysed Results
Decay occurs exponentially
Lifetime of sample A
Lifetime of sample B
The uncertainty was calculated using a stepwise
approach, taking pairs of points
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Errors Conclusion

• Darkroom did not cut out all light
• Method of calculating errors not best suited to
  data
• Alignment of laser through centre of crystal
  proved impossible

Conclusion Sample A (soft glass with 2 Er3) is
more suitable for use as an amplifier