Towards biological media assessment using wavefront shaping techniques
As light traverses through a random medium, its refractive indices are highly inconsistently distributed, resulting in light scattering. Controlling and investigating the scattering events is of paramount importance to improve image quality through a random medium such as biological tissue. Due to the composition, focusing and imaging through biological media has issues of strong scattering resulting in an entirely lost image. This task may be accomplished by reconfiguring every portion of the incoming wavefront differently to fit specific needs. Owing to the advances in wavefront shaping techniques, optical imaging of biological media can now be used for experimental studies without following invasive procedures. In this work, a spatial light modulator (SLM) was used to control phase and amplitude to focus light and perform imaging. We illuminated the phase-only SLM by He-Ne laser, after reflection from SLM light was directed into multi-mode fiber (which was used for testing). Light from the distal end was collected using a collimator and detected on CCD. CCD only estimated intensity values, so the double phase retrieval method retrieved the phase. Transmission matrix-based wavefront shaping methodology was deployed, which best described light propagation from SLM to CCD. Transmission coefficients' complex-valued matrix-related input and output fields have amplitude and phase information. Improvements in imaging can be made via a transmission matrix. Extracting such useful information helps prepare therapeutic protocols involving light and opens avenues for deep tissue imaging, photo-genetic therapy, and optogenetics control.