Optical phased arrays for wavefront shaping in forward scattering media

Area of Science:

• Biomedical Optics
• Integrated Photonics
• Microscopy

Background:

• High-resolution optical imaging in thick tissues is limited by light scattering.
• Conventional methods struggle with reduced non-scattered photons at depth.
• Wavefront shaping offers potential for deep-tissue imaging but requires hardware advancements.

Purpose of the Study:

• To compare different optical phased array (OPA) designs for focusing light in scattering media.
• To investigate OPA design trade-offs for improved performance in thick tissue-like samples.
• To assess the suitability of integrated photonics for in vivo microscopy applications.

Main Methods:

• Fabrication of OPAs on a silicon nitride (SiN) photonics platform at 852 nm wavelength.
• Experimental comparison of OPA designs with varying array pitch, antenna count, and emission profiles.
• Testing device performance with increasing thickness of forward-scattering samples.

Main Results:

• Demonstrated OPAs' ability to refocus scattered light in tissue-like samples.
• Identified key design trade-offs influencing OPA performance at different sample thicknesses.
• Observed two distinct performance regimes based on sample scattering properties.

Conclusions:

• Integrated photonics-based OPAs offer advantages in pixel pitch, speed, and compactness over spatial light modulators.
• OPA design optimization is crucial for effective deep-tissue optical focusing.
• SiN photonics platform is suitable for developing OPAs for NIR and VIS light applications in advanced microscopy.