Kerr - June 1, 2016

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Here is an outline to get started...let's evolve as project proceeds...media:160601_Kerr_Outline.docx

Part I – Become familiar with polarized light and optical measurements

Basic Setup
  • Find low power (<20 mW) laser and parts needed to do this:
  • Send light to power meter to get familiar with power level and control
  • Add a polarizer to define plane of polarization
  • Add an analyzer to find maximum and minimum e.g. “Law of Malus”
  • Between cross polarizers vary angle of half- and quarter- wave plates
  • Compare the different configurations to Thorlabs optical polarimeter
Photodiode and Scope Setup
  • Find a photodiode and scope to see intensity signal in real time
  • Define polarization and analyzing planes of crossed polarizers
  • Convince yourself that intervening half-wave plate can leak light
  • Insert Hinds AOM and demonstrate it works as a fast wave plate
  • Use lock-in amplifier to extract the AOM amplitude using photodiode
  • Compare the configuration to the Thorlabs optical polarimeter

Part II – Test Kerr signal using a magnetized foil

Basic Setup – Analyze linear polarization angle from iron foil
  • Find iron foils, pucks and permanent magnets
  • Reflect laser off un-magnetized iron foil between cross-polarizers
  • Use (variable) waveplate to test sensitivity to linear polarization plane
  • Test signal as permanent magnets are added (measure field) to foil
  • Move magnets relative to foil, test sensitivity
  • Learn how to demagnetize the foil
Advanced Setup – Photodiode and Scope Setup
  • Try Thorlabs polarimeter or fast photodiode to measure signal
  • Repeat basic setup using the Hinds modulator; vary the foil magnetization
  • Evolve sophistication of setup to best resolve plane of polarization

Part III – Kerr measurements of magnetized puck

Setup – Integrate your diagnostic at Magnet Measurement Facility (MMF)
  • Become familiar with the new magnet coil geometry, field
  • Devise a means to add your foil and with geometry like that of photogun
  • Move or re-build your Kerr diagnostic at the MMF
Experiment
  • Measure plane of polarization vs. power supply current (magnetic field)
  • With MMF help measure magnetic field at face of iron