Modified phase synthesis for a tunable vortex phase plate working on the Alvarez-Lohmann concept

Area of Science:

• Optics and Photonics
• Metamaterials and Nanophotonics

Background:

• The Alvarez-Lohmann (AL) concept describes a tunable element as two combined elements with transmittance matching a plane parallel plate.
• Vortex phase plates (VPPs) with tunable topological charge can be realized using the AL concept by shearing elements.
• Standard AL designs assume zero separation between elements, which is impractical due to finite element thickness and shearing space.

Purpose of the Study:

• To develop a method for designing the phase transmittance of the second element in an AL combination to accommodate finite separation.
• To enable the realization of VPPs with tunable topological charge despite inevitable element separation.
• To create additional space within the AL combination for potential future integration of a third element for polarization control.

Main Methods:

• The study proposes a modified phase distribution for the second element of the AL combination.
• This method corrects the phase transmittance to compensate for the non-zero separation distance.
• The design accounts for the physical constraints of element thickness and the space required for shearing.

Main Results:

• A design method is provided for a two-element tunable optical element that functions correctly with finite separation.
• The proposed phase correction allows for a practical realization of AL-based VPPs.
• The design inherently creates space for a potential third element, enhancing future device versatility.

Conclusions:

• The presented method offers a practical approach to realizing tunable vortex phase plates using the Alvarez-Lohmann concept.
• Accommodating finite element separation is crucial for the performance of such tunable optical elements.
• The design paves the way for advanced optical elements with integrated polarization manipulation capabilities.