I am trying to measure the Goos-Hanchen shift of a 632.8nm laser using the Kretschmann configuration. The polarization state is modulated by an optical chopper. The two states are coupled into a fibre optic cable and reflected off a gold film into a position sensing quadrant detector (PSD). The chopper outputs a reference signal to the lock-in. To calculate the goos-hanchen shift I need both the difference voltage output of the PSD and the sum output for each polarisation state. However, my lock-in only has 1 input, so I cannot measure all 4 variables simultaneously. When I measure them separately, my calculated GH shift is unsurprisingly completely off. How can I improve my measurements. Do I need multiple lock-ins?
Dear Thomas Knight
You may want to review following helpful information. It sounds like you are dealing with a complex setup for measuring the Goos-Hänchen (GH) shift in the Kretschmann configuration. While using multiple lock-in amplifiers is one potential solution, there are also alternative strategies to improve your measurements with a single lock-in amplifier. Here are some suggestions:
If these approaches do not yield satisfactory results, using multiple lock-in amplifiers to simultaneously measure the four variables could be a more straightforward solution, albeit at a higher cost. Each lock-in amplifier would be dedicated to a specific channel, allowing parallel measurement of the two polarization states and their respective sum and difference signals.
Whichever approach you choose, it's crucial to carefully calibrate and validate your system to ensure accurate and reliable measurements of the Goos-Hänchen shift.
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