High-speed alignment optimization of digital optical phase conjugation systems based on autocovariance analysis in...

Area of Science:

• Optics and Photonics
• Biomedical Optics
• Wavefront Engineering

Background:

• Digital optical phase conjugation (DOPC) is crucial for focusing light through scattering media, enabling various optical applications.
• Accurate wavefront recording and playback in DOPC systems depend on precise alignment of optical components, especially the spatial light modulator (SLM) and camera.
• Imprecise alignment limits the effectiveness of DOPC, particularly in thick scattering media.

Purpose of the Study:

• To present a novel digital compensation technique for optimizing SLM alignment in DOPC systems.
• To demonstrate improved focusing capabilities through thick scattering media using the developed technique.
• To quantify the enhancement in focal quality achieved by the optimized alignment.

Main Methods:

• Implementation of a digital compensation technique to optimize SLM alignment in five degrees of freedom.
• Utilizing time-reversal symmetry for wavefront playback after SLM optimization.
• Characterization of focusing through scattering media with a thickness of 5 mm and a transport scattering coefficient of 2.5 mm⁻¹.

Main Results:

• Successful focusing of light through 5 mm thick scattering media with a transport scattering coefficient of 2.5 mm⁻¹.
• Significant improvement in focal quality, measured by peak-to-background ratio, by several orders of magnitude compared to unoptimized alignment.
• Demonstration of the technique's efficacy in overcoming alignment challenges in DOPC systems.

Conclusions:

• The presented digital compensation technique effectively optimizes SLM alignment for DOPC.
• This optimization enables robust focusing through challenging scattering media.
• The method substantially enhances focal quality, broadening the applicability of DOPC in demanding optical scenarios.