Kerr - June 1, 2016

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