Method for auto-alignment of digital optical phase conjugation systems based on digital propagation

Area of Science:

• Optics and Photonics
• Biomedical Optics
• Digital Optical Systems

Background:

• Optical phase conjugation (OPC) is vital for applications like aberration correction.
• Digital optical phase conjugation (DOPC) offers enhanced reflectivity and wavefront manipulation for biomedical optics.
• Practical DOPC use is hindered by precise sensor-SLM alignment requirements.

Purpose of the Study:

• To develop an auto-alignment method for DOPC systems.
• To overcome the limitations imposed by sensor-SLM misalignment.
• To enhance the practical usability and robustness of DOPC systems.

Main Methods:

• Implemented digital light propagation for auto-correction of sensor-SLM misalignment.
• Tested the method with significant axial, rotational, and in-plane displacements.
• Quantified performance using peak-to-background ratio (PBR).

Main Results:

• Successfully achieved auto-alignment for DOPC systems with substantial sensor-SLM misalignment (axial ~1.5 cm, rotation/tip/tilt ~5°, in-plane ~5 mm).
• Attained a PBR exceeding 30% of the theoretical maximum.
• Demonstrated robustness against mechanical drifts.

Conclusions:

• The auto-alignment method significantly improves DOPC system robustness and practical utility.
• This technique enables reliable operation despite considerable sensor-SLM misalignment.
• The findings pave the way for broader applications of DOPC in fields like deep-tissue optical focusing.