Cuong Dang Group

Non-Invasive Focusing through Scattering Media

Linear Fluorescence Signal as Feedback

The contrast and mean of incoherent speckles, produced by the linear fluorescence within the scattering media, are utilized as feedback signals to optimize the input wavefront.

While increasing speckle contrast makes the focus tighter and increasing the speckle mean enhances the intensity, fine-tuning the contribution of these two factors in our two-step optimization is essential.

A micrometer focal spot size (down to 20 μm diameter) and high intensity (more than a 100-fold enhancement) inside the scattering media are achieved.

Moving the focusing spot on the other side of scattering media

Focus anywhere on the other side of scattering media

A 4f system, creating optical conjugate planes between SLM and scattering media, allow to move the focus spot in 3D space within the memory effect region

The advantages of the optical configuration and full digital control allow us to move the focus spot with high quality at the speed of SLM frame rate.

Multiple focusing spots are achieved simultaneously by combining multiple phase patterns on a single SLM.