Abstract
Focusing light deep inside living tissue has not been achieved despite its promise to play a central role in biomedical imaging, optical manipulation and therapy. To address this challenge, internal-guide-star-based wavefront engineering techniques--for example, time-reversed ultrasonically encoded (TRUE) optical focusing--were developed. The speeds of these techniques, however, were limited to no greater than 1 Hz, preventing them from in vivo applications. Here we improve the speed of optical focusing deep inside scattering media by two orders of magnitude, and focus diffuse light inside a dynamic scattering medium having a speckle correlation time as short as 5.6 ms, typical of living tissue. By imaging a target, we demonstrate the first focusing of diffuse light inside a dynamic scattering medium containing living tissue. Since the achieved focusing speed approaches the tissue decorrelation rate, this work is an important step towards in vivo deep tissue noninvasive optical imaging, optogenetics and photodynamic therapy.
Highlights
Focusing light deep inside living tissue has not been achieved despite its promise to play a central role in biomedical imaging, optical manipulation and therapy
We demonstrated timereversed ultrasonically encoded (TRUE) optical focusing inside a dynamic scattering medium composed of an intralipid-gelatin phantom (IP, thickness 1⁄4 1.5 mm, reduced scattering coefficient 1⁄4 0.98 mm À 1) and a ground glass diffuser
The diffuse light passing through the diffuser and the IP was collected by a lens L, and concentrated on the photorefractive crystal (PRC)
Summary
Focusing light deep inside living tissue has not been achieved despite its promise to play a central role in biomedical imaging, optical manipulation and therapy To address this challenge, internal-guide-star-based wavefront engineering techniques—for example, timereversed ultrasonically encoded (TRUE) optical focusing—were developed. The speed of TRUE focusing has been limited to no greater than 1 Hz19,24,25, due either to the slow response of the photorefractive PCM for analogue TRUE10,19,21, or to the low speed of data acquisition, processing and transfer among the digital camera, the computer and the SLM for digital TRUE24,25 To date, these technologies have been confined to experimentation with static scattering media, such as ground glass diffusers, translucent tapes, tissue-mimicking phantoms and ex vivo biological tissue, whose speckle correlation times are greater than[24 180] s.
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