Focusing through dynamic scattering media

Abstract

We demonstrate steady-state focusing of coherent light through dynamic scattering media. The phase of an incident beam is controlled both spatially and temporally using a reflective, 1020-segment MEMS spatial light modulator, using a coordinate descent optimization technique. We achieve focal intensity enhancement of between 5 and 400 for dynamic media with speckle decorrelation time constants ranging from 0.4 seconds to 20 seconds. We show that this optimization approach combined with a fast spatial light modulator enables focusing through dynamic media. The capacity to enhance focal intensity despite transmission through dynamic scattering media could enable advancement in biological microscopy and imaging through turbid environments.

Adaptive control of waveguide modes in a two-mode-fiber

“…We may also define a different optimization parameter that depends on both the coupling efficiency and the correlation with the desired mode patterns. Given the fact that the algorithm described here has been widely used for optical focusing through diffusive media [19][20][21][22][23][24][25][26][27], where optical power is a critical factor, the issue of coupling efficiency should not become a major hurdle for our AO-based approach.…”

“…However, the overall framework of the AObased approach should still apply. Again, this expectation is based on the successful demonstration of AO-based focusing [19][20][21][22][23][24][25][26][27], which involves hundreds, if not tens of thousands independent scattering channels.…”

“…In future, we expect the faster algorithms and methods described in [21,22,[24][25][26][27] should significantly improve the speed of selective mode excitation.…”

“…Conceptually, the aforementioned AO-based approach is similar to those used in scattering medium focusing [19][20][21][22][23][24][25][26][27], imaging [28][29][30][31], or particle manipulation [32]. The main difference is that we are primarily interested in achieving highly selective excitation of LP modes for communication and sensing purposes, i.e., optical "focusing" in modal domain.…”

Spatiotemporal control of light in turbid media

“…Popoff et al demonstrated that the WFS approach can be parallelized to measure a significant fraction of the medium's transmission matrix [18,19]. In view of biomedical applications, several research groups have developed techniques for highspeed focusing and transmission matrix measurements through turbid media [20][21][22][23]. Van Putten et al employed WFS to create a scattering lens for high-resolution imaging [24,25].…”