How do I use THORLABS FPC030 Fiber Paddle Controllers to achieve a desired polarization state? (THORLABS FPC030 Fiber Paddle Controllers Instruction Manual)

Answer

manuals.plus

Feb 23, 2025 - 11:18 PM

To achieve a desired polarization state using the THORLABS FPC030 Fiber Paddle Controllers, follow the procedure outlined in the instruction manual. Here are the steps:

1. Measure the total power out of the polarization controller (P0) using a power meter.

2. Direct the output beam (after the polarization controller) through a polarization analyzer. The analyzer should be aligned orthogonal to the desired polarization state. For example, if you want vertical polarization, the linear polarizer transmission axis must be horizontal.

3. Rotate the half-wave fiber paddle (middle paddle) across the full range while monitoring the output power through the analyzer (Pr). Leave the paddle fixed at the location of minimum power for the remainder of the procedure.

4. Use the two adjacent quarter-wave fiber paddles individually (only one at a time) until a lower minimum power is observed at the power meter. This may require numerous iterations to reach the desired polarization extinction ratio (Pr / P0).

5. If the desired polarization extinction (PE) ratio has not been achieved, you can try adjusting the middle paddle and/or start over from the beginning to ensure you are not stuck at a local minimum. In testing, a PE ratio of 1,000:1 (-30 dB) was achieved.

6. Once the desired polarization state is achieved, the output light will have the desired polarization state orthogonal to the analyzer.

Please note that all measurements were recorded at room temperature with the fiber taped to the optical table. Environmental effects such as temperature variations and vibration can potentially change the output polarization state. Additionally, the performance of the LPNIR100 polarizer within the analyzer may affect the polarization extinction ratio, so it is important to consider the specifications of the polarizer being used.

For more detailed information and theoretical background on the THORLABS FPC030 Fiber Paddle Controllers, please refer to the instruction manual provided.