345 Senior Design Project

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345 Senior Design Project

• Lasing Rare-earth doped microspheres

Lawrence Tai
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Introduction

• Under the direction of Professor Gary Eden, and
  those in the Laboratory of Optical Physics and
  Engineering, I attempted to create my own
  microspheres and to get them to lase

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Goals

• Etch fiber
• Create microsphere
• Pump sphere in attempt to get it to lase
• Test array of microspheres

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Background - Fiber

• ZBLAN Fiber (Zirconium, Barium, Lanthanum,
  Aluminum, and Sodium)
• Transmits better than Silica glass, and wider
  spectrum
• Fiber consists of coating, 125 µm cladding, and
  2 µm core.

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Background - Microspheres

• Good resonators with low losses
• High Q (quality) value
• Possibly uses in many different devices
• Optical communication devices
• Lasers
• High resolution spectroscopy

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Review of original design

• Hydrogen Torch
• Dye Laser
• Lens
• Fiber Holder

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Etching process

• Tetrahydrofuran (THF) Remove Coating
• Solution of 0.3M HCl and small amounts of Boric
  acid etch cladding
• Use DI water and Isopropynal to clean and dry
  fiber
• Also tested solutions such as HF, H2SO4, and
  another solution with HCl and ZrOCl2

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Etching Process
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Microsphere creation

• Used Hydrogen torch to create the microspheres

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Microspheres

• Holmium (Ho) doped ZBLAN
• Pump 645 nm Lase 550 nm
• Erbium (Er) doped ZBLAN
• Pump 800 nm Lase 540 nm

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Microspheres

• Whispering Gallery Modes
• Light traveling within surface boundary reflected
  at small angles
• Best way of achieving low losses

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Pump Laser

• Argon ion pumping a dye laser
• Unable to get dye laser to lase
• Pumps at 645 nm
• Argon ion pumping Tisapphire laser
• Pumps at 800 nm

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Pump Laser
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Possible tests

• Visual test should see green
• Spectrum with spectroscope to confirm visual test
• Power in/out

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Results

• Unfortunately not able to get microsphere to
  lase.
• Measured wavelength of pump laser -gt 800.6 nm
• Measured power of pump laser -gt 240 mW

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Results
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Possible explanations

• Unable to correctly couple the laser into the
  microsphere
• Hitting sphere head on possibly canceling out
  photons inside of microsphere
• Created a bad microsphere

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Challenges

• Finding correct etching process
• Dye Laser
• Size of fibers

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Successes

• Refined process of etching fibers
• Creation of microspheres

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Future work

• Get microsphere to lase
• Couple multiple microspheres and collect data.
• Creating an array of microspheres and getting
  them to lase.