Beam steering limitation of a Risley prism system due to total internal reflection

Area of Science:

• Optics and Photonics
• Optical Engineering
• Beam Steering Technology

Background:

• Risley prisms are widely used for beam steering applications.
• Total internal reflection (TIR) can limit the operational range of Risley prism systems.
• Understanding these limitations is crucial for designing effective wide-angle beam steering systems.

Purpose of the Study:

• To investigate the limitations imposed by total internal reflection on beam steering using Risley prisms.
• To analyze four typical Risley prism configurations.
• To provide guidance for selecting prism materials and geometries for wide-angle beam steering.

Main Methods:

• Nonparaxial ray tracing to calculate incident angles at prism exit surfaces.
• Comparison of calculated angles with the critical angle to identify TIR.
• Derivation of limitations based on opening angles, prism orientation, and deviation power.

Main Results:

• Ray deviation power reaches an extreme value at a specific limit for opening angles, dependent on prism material.
• Exceeding the limit value restricts prism relative orientation.
• Higher refractive index decreases the limit of opening angles but increases extreme deviation power.
• 21-21 and 12-21 configurations offer larger limits and extreme deviation power (up to 90°) compared to 21-12 and 12-12.

Conclusions:

• The 21-21 and 12-21 Risley prism configurations provide a greater margin for designing wide-angle beam steering systems.
• Material and geometric choices significantly impact the performance and limitations of Risley prism beam steering.
• This research guides the selection of optimal parameters for advanced beam steering applications.