Development of broadband Er-doped fibersource

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Development of broadband Er-doped fibersource

• PHYS 492 Senior Project
• by Hasan Esat KONDAKÇI
• Department of Physics, Bilkent University,
  Bilkent, Ankara

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Outline

• Introduction
• Basics and concepts
• Amplifier Gain
• Power Source
• Gain Saturation
• Experiment
• Experimental Setup
• Meanwavelength temperature dependence
• Pump power efficiency
• Conclusion
• Brief Summary

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Introduction

• A coherent optical amplifier is a device that
  increase the amplitude of an optical field while
  maintaining its phase.
• COPs are important for various apllications
  amplification of weak optical pulses such as
  those that travel through long a long length if
  optical fiber

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Basics and Concepts

• There are three types of photon-atom
  interactions
• Absorption of photons
• Stimulated emission
• Spontaneous emission

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Amplifier Gain

• Underlying principle for achieving the coherent
  amplification of light is light amplification by
  the stimulated emission of radiation
• in the process we get clone photon with same
  frequency, direction and polarization
• two photons can serve to stimulate the emission
  two additional photons and so on
• result is coherent light amplification

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Amplifier Gain (Contd)

• Coherent light amplification is due to when
  photon energy is nearly equal to the atomic
  transition energy level
• Essential is the presence of a greater number of
  atoms in the upper energy level
• Achieving such a population inversion requires a
  source of power to excite (pump) the atoms into
  the higher energy level

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Amplifier Power Source

• Laser amplifiers require an external source of
  power to provide energy
• The pump must provide a population inversion on
  the transition of interest
• Pumping may be achieved optically, electrically,
  chemically even by nuclear expansion
• Required conditions determined by rate equations
  which depends laser gain medium

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Amplifier Power Source (Contd)

• Rare-earth-doped silica fibers cab serve as
  useful amplifying media.
• Erbium doped fibre amplifier is the most deployed
  fibre amplifier
• Pumping is achieved by transmitting laser light

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Gain Saturation

• Ideal amplifiers have linear system that
  increases the amplitude of the input signal by a
  fixed factor, called amplifier gain
• Real coherent amplifiers deliver a gain frequency
  dependent
• For sufficiently high input amplitude real
  amplifiers may exhibit saturation
• Fails to increase in proportion to input amplitude

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Experiment

• ASE source experimental setup

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Forward Port Spectrum
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Backward Port Spectrum
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Forward Port Temperature Dependence
Pump diode current 100mA m -0.813/-0.609 ppm/C
Pump diode current 75mA m -5.34/-1.11 ppm/C
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Backward Port Temperature Dependence
Pump diode current 100mA m 2.90/-0.37 ppm/C
Pump diode current 75mA m 6.30/-1.91 ppm/C
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Output power vs pump power
Forward port m0.057 Efficiency5.7 Backward
Port m0.094 Efficiency9.4 Total eff15.1
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Labview Interface
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Labview Block Diagram
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Conclusion

• Linear temperature dependence
• Without saturation pumping in the range 0-500 mW
  for 175 cm Er doped fiber silica

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References

• http//www.sp.phy.cam.ac.uk/SiGe/Stimulated20Emi
  ssion.html
• Bahaa E. A. Saleh, Malvin Carl Teich
  "Fundamentals of Photonics
• Frank L. Pedrotti, Leno S. Pedrotti, Leno M.
  Pedrotti
• Introduction to Optics
• E. Desurvire "Rare-Earth Doped Fiber Lasers and
  Amplifiers"

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• Thank you for your attention

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Questions

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