wavefrontshaping

Wavefront shaping refers to techniques for controlling the phase and amplitude of an optical wavefront to compensate for distortions caused by scattering media. By using a spatial light modulator (SLM) to sculpt the input field, one can focus light through opaque structures.

In scattering media, multiple scattering scrambles phase, so a tight focus cannot be achieved with a conventional beam. Wavefront shaping relies on feedback from a detector or on a measured transmission matrix to optimize the input so that scattered waves interfere constructively at a target, creating a bright focus.

Common approaches use phase-only or amplitude-modulating SLMs. Methods include iterative optimization (sequential, partitioning, or genetic algorithms) and model-based techniques that estimate the transmission matrix T to compute the ideal input. Digital optical phase conjugation and time-reversal methods are related alternatives.

Limitations include the need for a quasi-static medium during optimization, limited spectral bandwidth, and finite degrees of freedom on the SLM. Performance degrades in dynamic tissues and off-axis fields; spatial resolution improves with more modes and higher signal-to-noise ratio.

Applications span biomedical imaging and therapy, deep-tissue fluorescence, endoscopic imaging, and communications through turbid media. Wavefront shaping can enable sharper imaging and targeted light delivery inside scattering samples.

The field originated in the mid-2000s with demonstrations by Vellekoop and Mosk showing focusing through opaque layers using feedback-based wavefront control. Since then, the approach has expanded to rapid pulse shaping, broadband control, and integration with computational imaging.