title: Focusing through dynamic tissue with millisecond digital optical phase conjugation.
abstract: Digital optical phase conjugation (DOPC) is a new technique employed in wavefront shaping and phase conjugation for focusing light through or within scattering media such as biological tissues. DOPC is particularly attractive as it intrinsically achieves a high fluence reflectivity in comparison to nonlinear optical approaches. However, the slow refresh rate of liquid crystal spatial light modulators and limitations imposed by computer data transfer speeds have thus far made it difficult for DOPC to achieve a playback latency of shorter than ~200 ms and, therefore, prevented DOPC from being practically applied to thick living samples. In this paper, we report a novel DOPC system that is capable of 5.3 ms playback latency. This speed improvement of almost 2 orders of magnitude is achieved by using a digital micromirror device, field programmable gate array (FPGA) processing, and a single-shot binary phase retrieval technique. With this system, we are able to focus through 2.3 mm living mouse skin with blood flowing through it (decorrelation time ~30 ms) and demonstrate that the focus can be maintained indefinitely-an important technological milestone that has not been previously reported, to the best of our knowledge.
authors.affiliation: Departments of Electrical Engineering and Bioengineering, California Institute of Technology, Pasadena, California 91125, USA ; Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing, China.
authors.forename: Daifa
authors.initials: D
authors.lastname: Wang
authors.affiliation: Departments of Electrical Engineering and Bioengineering, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Edward Haojiang
authors.initials: EH
authors.lastname: Zhou
authors.affiliation: Departments of Electrical Engineering and Bioengineering, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Joshua
authors.initials: J
authors.lastname: Brake
authors.affiliation: Departments of Electrical Engineering and Bioengineering, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Haowen
authors.initials: H
authors.lastname: Ruan
authors.affiliation: Departments of Electrical Engineering and Bioengineering, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Mooseok
authors.initials: M
authors.lastname: Jang
authors.affiliation: Departments of Electrical Engineering and Bioengineering, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Changhuei
authors.initials: C
authors.lastname: Yang