Equal-intensity beam splitter realization by wire grid polarizers for passive laser speckle reduction

Area of Science:

• Optics
• Photonics
• Laser Physics

Background:

• Laser speckle is a common interference pattern that degrades image quality in laser-based systems.
• Existing methods for speckle reduction often involve complex setups or active components.
• Equal-intensity beam splitters (EIBS) offer a passive approach to manipulate laser beams for improved quality.

Purpose of the Study:

• To propose and demonstrate a novel method for constructing an equal-intensity beam splitter (EIBS) using wire grid polarizers (WGPs).
• To investigate the effectiveness of the proposed EIBS in reducing laser speckle.
• To evaluate the structural simplicity of the WGP-based EIBS compared to existing technologies.

Main Methods:

• An EIBS was designed and fabricated using WGPs with specific orientations and high-reflectivity mirrors.
• Three incoherent laser sub-beams (LSBs) were generated by controlling optical path differences.
• The speckle contrast was measured in a simplified laser projection system before and after implementing the EIBS.

Main Results:

• The proposed EIBS successfully generated three LSBs with equal intensities.
• The speckle contrast was significantly reduced from 0.82 to 0.5 when using three incoherent LSBs.
• The WGP-based EIBS demonstrated a simpler structure compared to other EIBS implementations.

Conclusions:

• The WGP-based EIBS is a feasible and effective method for passive speckle reduction in laser systems.
• The proposed EIBS offers a simpler and potentially more cost-effective solution for improving laser beam quality.
• This technology has practical applications in laser projection and imaging systems where speckle is a concern.