Another, probably the best solution is an integrated reset-free high-speed rotator based on lithium niobate (LiNbO3).
Such a controller comprises three waveguide sections, two of which simulate a QWP, and one of which simulates an HWP.
However, instead of rotating the wave plates, two voltages and the electro-optic effect determine the relative orientation (effective optical axis) of each. Proper voltage adjustments can achieve endless rotation of each wave plate.
Such devices are fast, small, broadband, temperature insensitive and highly reliable. By using an x-cut, z-propagating waveguide and the changes in both, the ordinary and the extraordinary refractive indices due to the electro-optical effect through the off-diagonal r61 coefficient, an electrically tuned wave-plate can be constructed.
The orientation of each wave-plate is determined by two voltages, which can be simplified to an equation only having one variable, the angular orientation of the wave-plate to be adjusted by the control circuit.
Photoline technologies offer such a high speed rotator, the PL-LN series with rotation frequencies from 500 MHz up to 15 GHz, which extends the magnetic field sensor concept to a large bandwidth measurement system.
- Polarization rotators – Manuel polarization rotator (free-space)
- Polarization rotators – Piezo based polarization rotator