1
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Ding C, Shao R, He Q, Li LS, Yang J. Wavefront shaping improves the transparency of the scattering media: a review. JOURNAL OF BIOMEDICAL OPTICS 2024; 29:S11507. [PMID: 38089445 PMCID: PMC10711682 DOI: 10.1117/1.jbo.29.s1.s11507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/14/2023] [Revised: 11/21/2023] [Accepted: 11/22/2023] [Indexed: 12/18/2023]
Abstract
Significance Wavefront shaping (WFS) can compensate for distortions by optimizing the wavefront of the input light or reversing the transmission matrix of the media. It is a promising field of research. A thorough understanding of principles and developments of WFS is important for optical research. Aim To provide insight into WFS for researchers who deal with scattering in biomedicine, imaging, and optical communication, our study summarizes the basic principles and methods of WFS and reviews recent progress. Approach The basic principles, methods of WFS, and the latest applications of WFS in focusing, imaging, and multimode fiber (MMF) endoscopy are described. The practical challenges and prospects of future development are also discussed. Results Data-driven learning-based methods are opening up new possibilities for WFS. High-resolution imaging through MMFs can support small-diameter endoscopy in the future. Conclusion The rapid development of WFS over the past decade has shown that the best solution is not to avoid scattering but to find ways to correct it or even use it. WFS with faster speed, more optical modes, and more modulation degrees of freedom will continue to drive exciting developments in various fields.
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Affiliation(s)
- Chunxu Ding
- Shanghai Jiao Tong University, School of Electronic Information and Electrical Engineering, Shanghai, China
| | - Rongjun Shao
- Shanghai Jiao Tong University, School of Electronic Information and Electrical Engineering, Shanghai, China
| | - Qiaozhi He
- Shanghai Jiao Tong University, Institute of Marine Equipment, Shanghai, China
| | - Lei S. Li
- Rice University, Department of Electrical and Computer Engineering, Houston, Texas, United States
| | - Jiamiao Yang
- Shanghai Jiao Tong University, School of Electronic Information and Electrical Engineering, Shanghai, China
- Shanghai Jiao Tong University, Institute of Marine Equipment, Shanghai, China
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2
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Liang H, Li TJ, Luo J, Zhao J, Wang J, Wu D, Luo ZC, Shen Y. Optical focusing inside scattering media with iterative time-reversed ultrasonically encoded near-infrared light. OPTICS EXPRESS 2023; 31:18365-18378. [PMID: 37381549 DOI: 10.1364/oe.491462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Accepted: 05/03/2023] [Indexed: 06/30/2023]
Abstract
Focusing light inside scattering media is a long-sought goal in optics. Time-reversed ultrasonically encoded (TRUE) focusing, which combines the advantages of biological transparency of the ultrasound and the high efficiency of digital optical phase conjugation (DOPC) based wavefront shaping, has been proposed to tackle this problem. By invoking repeated acousto-optic interactions, iterative TRUE (iTRUE) focusing can further break the resolution barrier imposed by the acoustic diffraction limit, showing great potential for deep-tissue biomedical applications. However, stringent requirements on system alignment prohibit the practical use of iTRUE focusing, especially for biomedical applications at the near-infrared spectral window. In this work, we fill this blank by developing an alignment protocol that is suitable for iTRUE focusing with a near-infrared light source. This protocol mainly contains three steps, including rough alignment with manual adjustment, fine-tuning with a high-precision motorized stage, and digital compensation through Zernike polynomials. Using this protocol, an optical focus with a peak-to-background ratio (PBR) of up to 70% of the theoretical value can be achieved. By using a 5-MHz ultrasonic transducer, we demonstrated the first iTRUE focusing using near-infrared light at 1053 nm, enabling the formation of an optical focus inside a scattering medium composed of stacked scattering films and a mirror. Quantitatively, the size of the focus decreased from roughly 1 mm to 160 µm within a few consecutive iterations and a PBR up to 70 was finally achieved. We anticipate that the capability of focusing near-infrared light inside scattering media, along with the reported alignment protocol, can be beneficial to a variety of applications in biomedical optics.
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3
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Luo J, Liu Y, Wu D, Xu X, Shao L, Feng Y, Pan J, Zhao J, Shen Y, Li Z. High-speed single-exposure time-reversed ultrasonically encoded optical focusing against dynamic scattering. SCIENCE ADVANCES 2022; 8:eadd9158. [PMID: 36525498 DOI: 10.1126/sciadv.add9158] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Focusing light deep inside live scattering tissue promises to revolutionize biophotonics by enabling deep tissue noninvasive optical imaging, manipulation, and therapy. By combining with guide stars, wavefront shaping is emerging as a powerful tool to make scattering media optically transparent. However, for in vivo biomedical applications, the speeds of existing techniques are still too slow to accommodate the fast speckle decorrelation of live tissue. To address this key bottleneck, we develop a quaternary phase encoding scheme to enable single-exposure time-reversed ultrasonically encode optical focusing with full-phase modulations. Specifically, we focus light inside dynamic scattering media with an average mode time down to 29 ns, which indicates that more than 104 effective spatial modes can be controlled within 1 millisecond. With this technique, we demonstrate in vivo light focusing in between a highly opaque adult zebrafish of 5.1 millimeters in thickness and a ground glass diffuser. Our work presents an important step toward in vivo deep tissue applications of wavefront shaping.
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Affiliation(s)
- Jiawei Luo
- School of Electronics and Information Technology, Guangdong Provincial Key Laboratory of Optoelectronic Information Processing Chips and Systems, Sun Yat-sen University, Guangzhou, China
| | - Yan Liu
- School of Optometry, Indiana University, Bloomington, IN, USA
| | - Daixuan Wu
- School of Electronics and Information Technology, Guangdong Provincial Key Laboratory of Optoelectronic Information Processing Chips and Systems, Sun Yat-sen University, Guangzhou, China
| | - Xiao Xu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
- Department of Biomedical Engineering, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Lijie Shao
- Department of Geriatrics, The First Affiliated Hospital of University of Science and Technology of China, Hefei, China
| | - Yuanhua Feng
- Department of Electronic Engineering, College of Information Science and Technology, Jinan University, Guangzhou, China
| | - Jingshun Pan
- School of Electronics and Information Technology, Guangdong Provincial Key Laboratory of Optoelectronic Information Processing Chips and Systems, Sun Yat-sen University, Guangzhou, China
| | - Jiayu Zhao
- School of Electronics and Information Technology, Guangdong Provincial Key Laboratory of Optoelectronic Information Processing Chips and Systems, Sun Yat-sen University, Guangzhou, China
| | - Yuecheng Shen
- School of Electronics and Information Technology, Guangdong Provincial Key Laboratory of Optoelectronic Information Processing Chips and Systems, Sun Yat-sen University, Guangzhou, China
- State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou, China
| | - Zhaohui Li
- School of Electronics and Information Technology, Guangdong Provincial Key Laboratory of Optoelectronic Information Processing Chips and Systems, Sun Yat-sen University, Guangzhou, China
- State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou, China
- Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai, China
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4
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Liu L, Liang W, Qu Y, He Q, Shao R, Ding C, Yang J. Anti-scattering light focusing with full-polarization digital optical phase conjugation based on digital micromirror devices. OPTICS EXPRESS 2022; 30:31614-31622. [PMID: 36242240 DOI: 10.1364/oe.467444] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Accepted: 08/09/2022] [Indexed: 06/16/2023]
Abstract
The high resolution of optical imaging and optogenetic stimulation in the deep tissue requires focusing light against strong scattering with high contrast. Digital optical phase conjugation (DOPC) has emerged recently as a promising solution for this requirement, because of its short latency. A digital micromirror device (DMD) in the implementation of DOPC enables a large number of modulation modes and a high speed of modulation both of which are important when dealing with a highly dynamic scattering medium. Here, we propose full-polarization DOPC (fpDOPC) in which two DMDs simultaneously modulate the two orthogonally polarized components of the optical field, respectively, to mitigate the effect of depolarization caused by strong scattering. We designed a simple system to overcome the difficulty of alignment encountered when modulating two polarized components independently. Our simulation and experiment showed that fpDOPC could generate a high-contrast focal spot, even though the polarization of light had been highly randomized by scattering. In comparison with the conventional method of modulating the polarization along a particular direction, fpDOPC can improve the peak to background ratio of the focal spot by a factor of two. This new technique has good potential in applications such as high-contrast light focusing in vivo.
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5
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Dou J, Ma C, Wang K, Di J, Zhang J, Zhao J. Light-field focusing and modulation through scattering media based on dual-polarization-encoded digital optical phase conjugation. OPTICS LETTERS 2022; 47:2738-2741. [PMID: 35648918 DOI: 10.1364/ol.461029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 05/08/2022] [Indexed: 06/15/2023]
Abstract
Digital optical phase conjugation (DOPC) can be applied for light-field focusing and imaging through or within scattering media. Traditional DOPC only recovers the phase but loses the polarization information of the original incident beam. In this Letter, we propose a dual-polarization-encoded DOPC to recover the full information (both phase and polarization) of the incident beam. The phase distributions of two orthogonal polarization components of the speckle field coming from a multimode fiber are first measured by using digital holography. Then, the phase distributions are separately modulated on two beams and their conjugations are superposed to recover the incident beam through the fiber. By changing the phase difference or amplitude ratio between the two conjugate beams, light fields with complex polarization distribution can also be generated. This method will broaden the application scope of DOPC in imaging through scattering media.
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6
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Focusing of a Laser Beam Passed through a Moderately Scattering Medium Using Phase-Only Spatial Light Modulator. PHOTONICS 2022. [DOI: 10.3390/photonics9050296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The rarely considered case of laser beam propagation and focusaing through the moderately scattering medium was researched. A phase-only spatial light modulator (SLM) with 1920×1080 pixel resolution was used to increase the efficiency of focusing of laser radiation propagated through the 5 mm layer of the scattering suspension of 1 µm polystyrene microbeads in distilled water with the concentration values ranging from 105 to 106 mm−3. A CCD camera with micro-objective was used to estimate the intensity distribution of the far-field focal spot. A Shack-Hartmann sensor was used to measure wavefront distortions. The conducted experimental research demonstrated the 8% increase in integral intensity and 16% decrease in diameter of the far-field focal spot due to the use of the SLM for laser beam focusing.
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7
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Zhou Y, Braverman B, Fyffe A, Zhang R, Zhao J, Willner AE, Shi Z, Boyd RW. High-fidelity spatial mode transmission through a 1-km-long multimode fiber via vectorial time reversal. Nat Commun 2021; 12:1866. [PMID: 33767150 PMCID: PMC7994418 DOI: 10.1038/s41467-021-22071-w] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 02/24/2021] [Indexed: 11/30/2022] Open
Abstract
The large number of spatial modes supported by standard multimode fibers is a promising platform for boosting the channel capacity of quantum and classical communications by orders of magnitude. However, the practical use of long multimode fibers is severely hampered by modal crosstalk and polarization mixing. To overcome these challenges, we develop and experimentally demonstrate a vectorial time reversal technique, which is accomplished by digitally pre-shaping the wavefront and polarization of the forward-propagating signal beam to be the phase conjugate of an auxiliary, backward-propagating probe beam. Here, we report an average modal fidelity above 80% for 210 Laguerre-Gauss and Hermite-Gauss modes by using vectorial time reversal over an unstabilized 1-km-long fiber. We also propose a practical and scalable spatial-mode-multiplexed quantum communication protocol over long multimode fibers to illustrate potential applications that can be enabled by our technique. The use of long multimode fibers for multiplexed quantum communication is hindered by modal crosstalk and polarisation mixing. Here, the authors use an auxiliary laser beam sent backwards from Bob to Alice, allowing her to pre-compensate for the spatial distortions and polarisation scrambling.
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Affiliation(s)
- Yiyu Zhou
- The Institute of Optics, University of Rochester, Rochester, NY, USA.
| | - Boris Braverman
- Department of Physics, University of Ottawa, Ottawa, ON, Canada
| | - Alexander Fyffe
- Department of Physics, University of South Florida, Tampa, FL, USA
| | - Runzhou Zhang
- Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, USA
| | - Jiapeng Zhao
- The Institute of Optics, University of Rochester, Rochester, NY, USA
| | - Alan E Willner
- Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, USA
| | - Zhimin Shi
- Department of Physics, University of South Florida, Tampa, FL, USA
| | - Robert W Boyd
- The Institute of Optics, University of Rochester, Rochester, NY, USA.,Department of Physics, University of Ottawa, Ottawa, ON, Canada
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8
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Galaktionov I, Sheldakova J, Nikitin A, Samarkin V, Parfenov V, Kudryashov A. Laser beam focusing through a moderately scattering medium using a bimorph mirror. OPTICS EXPRESS 2020; 28:38061-38075. [PMID: 33379626 DOI: 10.1364/oe.408899] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 11/18/2020] [Indexed: 06/12/2023]
Abstract
The rarely considered case when the optical radiation passes through the weakly scattering medium, e.g. mid-density atmospheric fog with the number of scattering events up to 10 was investigated in this paper. We demonstrated an improvement of focusing of a laser beam (λ=0.65 µm) passed through the 5 mm-thick layer of scattering suspension of 1 µm polystyrene microbeads diluted in a distilled water. For the first time the low-order aberration corrector - wide aperture bimorph deformable mirror with 48 electrodes configured in 6 rings was used to optimize a far-field focal spot. We compared efficiencies of the algorithm that optimized the positions of the focal spots on Shack-Hartmann type sensor and the algorithm that optimized the peak brightness and the diameter of the far-field focal spot registered with a CCD. We experimentally demonstrated the increase of the peak brightness of the far-field focal spot by up to 60% due to the use of the bimorph deformable mirror for beam focusing through the scattering medium with concentration values of scatterers ranged from 105 to 106 mm-3.
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9
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Mididoddi CK, Lennon RA, Li S, Phillips DB. High-fidelity off-axis digital optical phase conjugation with transmission matrix assisted calibration. OPTICS EXPRESS 2020; 28:34692-34705. [PMID: 33182931 DOI: 10.1364/oe.409226] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 10/12/2020] [Indexed: 06/11/2023]
Abstract
The spatial information carried by light is scrambled when it propagates through a scattering medium, such as frosted glass, biological tissue, turbulent air, or multimode optical fibres. Digital optical phase conjugation (DOPC) is a technique that 'pre-aberrates' an illuminating wavefront to compensate for scatterer induced distortion. DOPC systems act as phase-conjugate mirrors: they require a camera to holographically record a distorted wavefront emanating from the scatterer and a spatial light modulator (SLM) to synthesize a phase conjugate of the measured wavefront, which is sent back through the scatterer thus creating a time-reversed copy of the original optical field. High-fidelity DOPC can be technically challenging to achieve as it typically requires pixel-perfect alignment between the camera and SLM. Here we describe a DOPC system in which the normally stringent alignment criteria are relaxed. In our system the SLM and camera are placed in-line in the same optical path from the sample, and the SLM is used in an off-axis configuration. This means high-precision alignment can be achieved by measurement of the transmission matrix (TM) mapping optical fields from the SLM to the camera and vice-versa, irrespective of their relative position. The TM also absorbs and removes other aberrations in the optical system, such as the curvature of the SLM and camera chips. Using our system we demonstrate high-fidelity focussing of light through two ground glass diffusers with a peak-intensity to mean-background ratio of ∼700. We provide a step-by-step guide detailing how to align this system and discuss the trade-offs with alternative configurations. We also describe how our setup can be used as a 'single-pixel camera' based DOPC system, offering potential for DOPC at wavelengths in which cameras are not available or are prohibitively expensive.
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10
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Cheng Z, Yang J, Wang LV. Single-shot time-reversed optical focusing into and through scattering media. ACS PHOTONICS 2020; 7:2871-2877. [PMID: 34337103 PMCID: PMC8317964 DOI: 10.1021/acsphotonics.0c01154] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Optical time reversal can focus light through or into scattering media, which raises a new possibility for conquering optical diffusion. Because optical time reversal must be completed within the correlation time of speckles, enhancing the speed of time-reversed optical focusing is important for practical applications. Although employing faster digital devices for time-reversal helps, more efficient methodologies are also desired. Here, we report a single-shot time-reversed optical focusing method to minimize the wavefront measurement time. In our approach, all information requisite for optical time reversal is extracted from a single-shot hologram, and hence no other preconditions or measurements are required. In particular, we demonstrate the first realization of single-shot time-reversed ultrasonically encoded (TRUE) optical focusing into scattering media. By using the minimum amount of measurement, this work breaks the fundamental speed limit of digitally based time reversal for focusing into and through scattering media, and constitutes an important step toward high-speed wavefront shaping applications.
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11
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Li R, Peng T, Zhou M, Yu X, Min J, Yang Y, Yao B. Full-polarization wavefront shaping for imaging through scattering media. APPLIED OPTICS 2020; 59:5131-5135. [PMID: 32543531 DOI: 10.1364/ao.391909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 05/11/2020] [Indexed: 06/11/2023]
Abstract
The scattering effect occurring when light passes through inhomogeneous-refractive-index media such as atmosphere or biological tissues will scramble the light wavefront into speckles and impede optical imaging. Wavefront shaping is an emerging technique for imaging through scattering media that works by addressing correction of the disturbed wavefront. In addition to the phase and amplitude, the polarization of the output scattered light will also become spatially randomized in some cases. The recovered image quality and fidelity benefit from correcting as much distortion of the scattered light as possible. Liquid-crystal spatial light modulators (LC-SLMs) are widely used in the wavefront shaping technique, since they can provide a great number of controlled modes and thereby high-precision wavefront correction. However, due to the working principle of LC-SLMs, the wavefront correction is restricted to only one certain linear polarization state, resulting in retrieved image information in only the right polarization, while the information in the orthogonal polarization is lost. In this paper, we describe a full-polarization wavefront correction system for shaping the scattered light wavefront in two orthogonal polarizations with a single LC-SLM. The light speckles in both polarizations are corrected for retrieval of the full polarization information and faithful images of objects. As demonstrated in the experiments, the focusing intensity can be increased by full-polarization wavefront correction, images of objects in arbitrary polarization states can be retrieved, and the polarization state of the object's light can also be recognized.
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12
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Cheng Z, Yang J, Wang LV. Intelligently optimized digital optical phase conjugation with particle swarm optimization. OPTICS LETTERS 2020; 45:431-434. [PMID: 32747844 PMCID: PMC7398265 DOI: 10.1364/ol.381930] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Accepted: 12/08/2019] [Indexed: 05/24/2023]
Abstract
Wavefront shaping (WFS) based on digital optical phase conjugation (DOPC) has gained major interest in focusing light through or inside scattering media. However, the quality of DOPC is greatly limited by imperfections of the system in a complicated and coupled way. In this Letter, we incorporate the concept of global optimization to solve this problem comprehensively for the first time, to the best of our knowledge. An automatic and intelligent optimization framework for DOPC techniques is proposed, leveraging the global optimization ability of particle swarm optimization (PSO). We demonstrate the general and powerful ability of the proposed approach in a series of DOPC-related experiments for focusing through and inside scattering media. This novel work can improve the OPC quality greatly and simplify the development of a high-performance DOPC system, which may open up a new avenue for the general scientific community to benefit from DOPC-based WFS in their potential applications.
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13
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Feng Q, Yang F, Xu X, Zhang B, Ding Y, Liu Q. Multi-objective optimization genetic algorithm for multi-point light focusing in wavefront shaping. OPTICS EXPRESS 2019; 27:36459-36473. [PMID: 31873425 DOI: 10.1364/oe.27.036459] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 11/18/2019] [Indexed: 06/10/2023]
Abstract
We introduce a new multi-objective genetic algorithm for wavefront shaping and realize controllable multi-point light focusing through scattering medium. Different from previous single-objective optimization genetic algorithms, our algorithm named Non-dominated Sorting Genetic Algorithm II based on hybrid optimization scheme (NSGA2-H) can make all focus points have uniform intensity while ensuring that their enhancement is as high as possible. We demonstrate the characteristics of NSGA2-H through simulations and experiments in amplitude optimization, analyze its optimization mechanisms and show its powerful optical control capability in uniform intensity focusing and even in customizable intensity focusing. This research will be expected to further promote future practical applications based on multi-point focusing of wavefront shaping, especially in optical trapping and optogenetics.
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14
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Yang J, Li L, Shemetov AA, Lee S, Zhao Y, Liu Y, Shen Y, Li J, Oka Y, Verkhusha VV, Wang LV. Focusing light inside live tissue using reversibly switchable bacterial phytochrome as a genetically encoded photochromic guide star. SCIENCE ADVANCES 2019; 5:eaay1211. [PMID: 31844671 PMCID: PMC6905864 DOI: 10.1126/sciadv.aay1211] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Accepted: 10/09/2019] [Indexed: 05/14/2023]
Abstract
Focusing light deep by engineering wavefronts toward guide stars inside scattering media has potential biomedical applications in imaging, manipulation, stimulation, and therapy. However, the lack of endogenous guide stars in biological tissue hinders its translations to in vivo applications. Here, we use a reversibly switchable bacterial phytochrome protein as a genetically encoded photochromic guide star (GePGS) in living tissue to tag photons at targeted locations, achieving light focusing inside the tissue by wavefront shaping. As bacterial phytochrome-based GePGS absorbs light differently upon far-red and near-infrared illumination, a large dynamic absorption contrast can be created to tag photons inside tissue. By modulating the GePGS at a distinctive frequency, we suppressed the competition between GePGS and tissue motions and formed tight foci inside mouse tumors in vivo and acute mouse brain tissue, thus improving light delivery efficiency and specificity. Spectral multiplexing of GePGS proteins with different colors is an attractive possibility.
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Affiliation(s)
- Jiamiao Yang
- Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering, Department of Electrical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Lei Li
- Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering, Department of Electrical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Anton A. Shemetov
- Department of Anatomy and Structural Biology, and Gruss Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Sangjun Lee
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Yuan Zhao
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Yan Liu
- Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering, Department of Electrical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Yuecheng Shen
- Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering, Department of Electrical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Jingwei Li
- Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering, Department of Electrical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Yuki Oka
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Vladislav V. Verkhusha
- Department of Anatomy and Structural Biology, and Gruss Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Lihong V. Wang
- Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering, Department of Electrical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
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15
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Li J, Wei H, Li Y. Beam drift reduction by straightness measurement based on a digital optical phase conjugation. APPLIED OPTICS 2019; 58:7636-7642. [PMID: 31674420 DOI: 10.1364/ao.58.007636] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Accepted: 08/26/2019] [Indexed: 06/10/2023]
Abstract
One of the greatest challenges of long distance measurement is the beam drift caused by the air refractive index gradient. It has been established in many researches that optical phase conjugation (OPC) can be used to compensate for the beam bending. However, this method is limited to responding speed, phase conjugate reflectivity, flexibility, and specific source and medium. To reduce beam drift, instead of OPC, this study applies a digital OPC (DOPC) method, which is also creatively applied to collimation and flatness measurements. The main devices in the wavefront correction unit are the spatial light modulator and the Shack-Hartmann wavefront sensor. For the straightness measurement unit, the collimation and flatness of the optical rail are measured through the prism system and a position-sensing detector. After wavefront compensation, the root mean square is decreased from 0.0029λ to 0.0005λ. The beam drift is decreased from 1.22 mm to 0.70 mm in the x direction and from 2.49 mm to 1.55 mm in the y direction. The experimental data indicate that the straightness measurement system based on DOPC can effectively decrease the beam drift.
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16
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Cheng Z, Yang J, Wang LV. Dual-polarization analog optical phase conjugation for focusing light through scattering media. APPLIED PHYSICS LETTERS 2019; 114:231104. [PMID: 31312071 PMCID: PMC6565428 DOI: 10.1063/1.5097181] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 05/25/2019] [Indexed: 05/16/2023]
Abstract
Focusing light through or inside scattering media by the analog optical phase conjugation (AOPC) technique based on photorefractive crystals (PRCs) has been intensively investigated due to its high controlled degrees of freedom and short response time. However, the existing AOPC systems only phase-conjugate the scattered light in one polarization direction, while the polarization state of light scattered through a thick scattering medium is spatially random in general, which means that half of the scattering information is lost. Here, we propose dual-polarization AOPC for focusing light through scattering media to improve the efficiency and fidelity in the phase conjugation. The motivations of the dual-polarization AOPC are illustrated by theoretical analysis and numerical simulation, and then an experimental system is established to realize the dual-polarization AOPC. By separating and rotating the two orthogonal polarization components of the randomly polarized scattered light, light in all polarization states is recorded and phase-conjugated using the same PRC. Experimental results for focusing through a thick biological tissue show that the intensity of the time-reversed focus from the dual-polarization AOPC can be enhanced by a factor of approximate four compared with the existing single-polarization AOPC.
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17
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Yang J, Li J, He S, Wang LV. Angular-spectrum modeling of focusing light inside scattering media by optical phase conjugation. OPTICA 2019; 6:250-256. [PMID: 32025534 PMCID: PMC7002031 DOI: 10.1364/optica.6.000250] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Accepted: 01/29/2019] [Indexed: 05/24/2023]
Abstract
Focusing light inside scattering media by optical phase conjugation has been intensively investigated due to its potential applications, such as in deep tissue imaging. However, no existing physical models explain the impact of the various factors on the focusing performance inside a dynamic scattering medium. Here, we establish an angular- spectrum model to trace the field propagation during the entire optical phase conjugation process in the presence of scattering media. By incorporating fast decorrelation components, the model enables us to investigate the com- petition between the guide star and fast tissue motions for photon tagging. Other factors affecting the focusing performance are also analyzed via the model. As a proof of concept, we experimentally verify our model in the case of focusing light through dynamic scattering media. This angular-spectrum model allows analysis of a series of scattering events in highly scattering media and benefits related applications.
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Affiliation(s)
- Jiamiao Yang
- Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering, Department of Electrical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Jingwei Li
- Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering, Department of Electrical Engineering, California Institute of Technology, Pasadena, California 91125, USA
- Centre for Optical and Electromagnetic Research, Chinese National Engineering Research Center for Optical Instruments, Zhejiang University, Hangzhou 310058, China
| | - Sailing He
- Centre for Optical and Electromagnetic Research, Chinese National Engineering Research Center for Optical Instruments, Zhejiang University, Hangzhou 310058, China
| | - Lihong V. Wang
- Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering, Department of Electrical Engineering, California Institute of Technology, Pasadena, California 91125, USA
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18
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Yu Z, Xia M, Li H, Zhong T, Zhao F, Deng H, Li Z, Li D, Wang D, Lai P. Implementation of digital optical phase conjugation with embedded calibration and phase rectification. Sci Rep 2019; 9:1537. [PMID: 30733574 PMCID: PMC6367509 DOI: 10.1038/s41598-018-38326-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Accepted: 12/13/2018] [Indexed: 11/16/2022] Open
Abstract
Focused and controllable optical delivery beyond the optical diffusion limit in biological tissue has been desired for long yet considered challenging. Digital optical phase conjugation (DOPC) has been proven promising to tackle this challenge. Its broad applications, however, have been hindered by the system’s complexity and rigorous requirements, such as the optical beam quality, the pixel match between the wavefront sensor and wavefront modulator, as well as the flatness of the modulator’s active region. In this paper, we present a plain yet reliable DOPC setup with an embedded four-phase, non-iterative approach that can rapidly compensate for the wavefront modulator’s surface curvature, together with a non-phase-shifting in-line holography method for optical phase conjugation in the absence of an electro-optic modulator (EOM). In experiment, with the proposed setup the peak-to-background ratio (PBR) of optical focusing through a standard ground glass in experiment can be improved from 460 up to 23,000, while the full width at half maximum (FWHM) of the focal spot can be reduced from 50 down to 10 μm. The focusing efficiency, as measured by the value of PBR, reaches nearly 56.5% of the theoretical value. Such a plain yet efficient implementation, if further engineered, may potentially boost DOPC suitable for broader applications.
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Affiliation(s)
- Zhipeng Yu
- Department of Biomedical Engineering, Hong Kong Polytechnic University, Hong Kong, Hong Kong.,Shenzhen Research Institute, Hong Kong Polytechnic University, Shenzhen, 518057, China
| | - Meiyun Xia
- School of Biological Science and Medical Engineering, Beihang University, Beijing, 100083, China.,Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing, 100083, China
| | - Huanhao Li
- Department of Biomedical Engineering, Hong Kong Polytechnic University, Hong Kong, Hong Kong.,Shenzhen Research Institute, Hong Kong Polytechnic University, Shenzhen, 518057, China
| | - Tianting Zhong
- Department of Biomedical Engineering, Hong Kong Polytechnic University, Hong Kong, Hong Kong.,Shenzhen Research Institute, Hong Kong Polytechnic University, Shenzhen, 518057, China
| | - Fangyuan Zhao
- School of Biological Science and Medical Engineering, Beihang University, Beijing, 100083, China.,Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing, 100083, China
| | - Hao Deng
- School of Biological Science and Medical Engineering, Beihang University, Beijing, 100083, China
| | - Zihao Li
- Department of Biomedical Engineering, Hong Kong Polytechnic University, Hong Kong, Hong Kong
| | - Deyu Li
- School of Biological Science and Medical Engineering, Beihang University, Beijing, 100083, China.,Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing, 100083, China
| | - Daifa Wang
- School of Biological Science and Medical Engineering, Beihang University, Beijing, 100083, China.,Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing, 100083, China
| | - Puxiang Lai
- Department of Biomedical Engineering, Hong Kong Polytechnic University, Hong Kong, Hong Kong. .,Shenzhen Research Institute, Hong Kong Polytechnic University, Shenzhen, 518057, China.
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19
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Ma C, Di J, Zhang Y, Li P, Xiao F, Liu K, Bai X, Zhao J. Reconstruction of structured laser beams through a multimode fiber based on digital optical phase conjugation. OPTICS LETTERS 2018; 43:3333-3336. [PMID: 30004499 DOI: 10.1364/ol.43.003333] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2018] [Accepted: 06/16/2018] [Indexed: 06/08/2023]
Abstract
The digital optical phase conjugation (DOPC) technique is being actively developed for optical focusing and imaging through or inside complex media. Due to its time-reversal nature, DOPC has been exploited to regenerate different intensity targets. However, whether the targets with three-dimensional information through complex media could be recovered has not been experimentally demonstrated, to the best of our knowledge. Here, we present a method to regenerate structured laser beams based on DOPC. Although only the phase of the original scattered wave is time reversed, the reconstruction of a quasi-Bessel beam and vortex beams through a multimode fiber (MMF) is demonstrated. The regenerated quasi-Bessel beam shows the features of sub-diffraction focusing and a longer depth of field with respect to a Gaussian beam. Moreover, the reconstruction of vortex beams shows the fidelity of DOPC both in amplitude and phase, which is demonstrated for the first time, to the best of our knowledge. We also prove that the reconstruction results of DOPC through the MMF are indeed phase conjugate to the original targets. We expect that these results could be useful in super-resolution imaging and optical micromanipulation through complex media, and further pave the way for achieving three-dimensional imaging based on DOPC.
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20
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Qu Y, Li L, Shen Y, Wei X, Wong TT, Hu P, Yao J, Maslov K, Wang LV. Dichroism-sensitive photoacoustic computed tomography. OPTICA 2018; 5:495-501. [PMID: 30820444 PMCID: PMC6388697 DOI: 10.1364/optica.5.000495] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Photoacoustic computed tomography (PACT), a fast-developing modality for deep tissue imaging, images the spatial distribution of optical absorption. PACT usually treats the absorption coefficient as a scalar. However, the absorption coefficients of many biological tissues exhibit an anisotropic property, known as dichroism or diattenuation, which depends on molecular conformation and structural alignment. Here we present a novel imaging method called dichroism-sensitive PACT (DS-PACT), which measures both the amplitude of tissue's dichroism and the orientation of the optic axis of uniaxial dichroic tissue. By modulating the polarization of linearly polarized light and measuring the alternating signals through lock-in detection, DS-PACT can boost dichroic signals from biological tissues. To validate the proposed approach, we experimentally demonstrated the performance of DS-PACT by imaging plastic polarizers and ex vivo bovine tendons deep inside scattering media. We successfully detected the orientation of the optic axis of uniaxial dichroic materials, even at a depth of 4.5 transport mean free paths. We anticipate that the proposed method will extend the capability of PACT to imaging tissue absorption anisotropy.
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Affiliation(s)
- Yuan Qu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, USA
| | - Lei Li
- Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering and Department of Electrical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Yuecheng Shen
- Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering and Department of Electrical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Xiaoming Wei
- Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering and Department of Electrical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Terence T.W. Wong
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, USA
- Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering and Department of Electrical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Peng Hu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, USA
| | - Junjie Yao
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, USA
| | - Konstantin Maslov
- Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering and Department of Electrical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Lihong V. Wang
- Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering and Department of Electrical Engineering, California Institute of Technology, Pasadena, California 91125, USA
- Corresponding author:
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21
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Liu Y, Shen Y, Ruan H, Brodie FL, Wong TTW, Yang C, Wang LV. Time-reversed ultrasonically encoded optical focusing through highly scattering ex vivo human cataractous lenses. JOURNAL OF BIOMEDICAL OPTICS 2018; 23:1-4. [PMID: 29322749 PMCID: PMC5762002 DOI: 10.1117/1.jbo.23.1.010501] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 12/01/2017] [Indexed: 06/07/2023]
Abstract
Normal development of the visual system in infants relies on clear images being projected onto the retina, which can be disrupted by lens opacity caused by congenital cataract. This disruption, if uncorrected in early life, results in amblyopia (permanently decreased vision even after removal of the cataract). Doctors are able to prevent amblyopia by removing the cataract during the first several weeks of life, but this surgery risks a host of complications, which can be equally visually disabling. Here, we investigated the feasibility of focusing light noninvasively through highly scattering cataractous lenses to stimulate the retina, thereby preventing amblyopia. This approach would allow the cataractous lens removal surgery to be delayed and hence greatly reduce the risk of complications from early surgery. Employing a wavefront shaping technique named time-reversed ultrasonically encoded optical focusing in reflection mode, we focused 532-nm light through a highly scattering ex vivo adult human cataractous lens. This work demonstrates a potential clinical application of wavefront shaping techniques.
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Affiliation(s)
- Yan Liu
- California Institute of Technology, Department of Electrical Engineering, Pasadena, California, United States
| | - Yuecheng Shen
- California Institute of Technology, Andrew and Peggy Cherng Department of Medical Engineering, Pasadena, California, United States
| | - Haowen Ruan
- California Institute of Technology, Department of Electrical Engineering, Pasadena, California, United States
| | - Frank L. Brodie
- University of California, San Francisco, Department of Ophthalmology, San Francisco, California, United States
| | - Terence T. W. Wong
- California Institute of Technology, Andrew and Peggy Cherng Department of Medical Engineering, Pasadena, California, United States
| | - Changhuei Yang
- California Institute of Technology, Department of Electrical Engineering, Pasadena, California, United States
- California Institute of Technology, Andrew and Peggy Cherng Department of Medical Engineering, Pasadena, California, United States
| | - Lihong V. Wang
- California Institute of Technology, Department of Electrical Engineering, Pasadena, California, United States
- California Institute of Technology, Andrew and Peggy Cherng Department of Medical Engineering, Pasadena, California, United States
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22
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Yang J, Shen Y, Liu Y, Hemphill AS, Wang LV. Focusing light through scattering media by polarization modulation based generalized digital optical phase conjugation. APPLIED PHYSICS LETTERS 2017; 111:201108. [PMID: 29203931 PMCID: PMC5690666 DOI: 10.1063/1.5005831] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 10/27/2017] [Indexed: 05/13/2023]
Abstract
Optical scattering prevents light from being focused through thick biological tissue at depths greater than ∼1 mm. To break this optical diffusion limit, digital optical phase conjugation (DOPC) based wavefront shaping techniques are being actively developed. Previous DOPC systems employed spatial light modulators that modulated either the phase or the amplitude of the conjugate light field. Here, we achieve optical focusing through scattering media by using polarization modulation based generalized DOPC. First, we describe an algorithm to extract the polarization map from the measured scattered field. Then, we validate the algorithm through numerical simulations and find that the focusing contrast achieved by polarization modulation is similar to that achieved by phase modulation. Finally, we build a system using an inexpensive twisted nematic liquid crystal based spatial light modulator (SLM) and experimentally demonstrate light focusing through 3-mm thick chicken breast tissue. Since the polarization modulation based SLMs are widely used in displays and are having more and more pixel counts with the prevalence of 4 K displays, these SLMs are inexpensive and valuable devices for wavefront shaping.
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Affiliation(s)
| | | | - Yan Liu
- Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St Louis, Campus Box 1097, One Brookings Drive, St Louis, Missouri 63130, USA
| | - Ashton S Hemphill
- Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St Louis, Campus Box 1097, One Brookings Drive, St Louis, Missouri 63130, USA
| | - Lihong V Wang
- Caltech Optical Imaging Laboratory, Andrew and Peggy Cherng Department of Medical Engineering, Department of Electrical Engineering, California Institute of Technology, Pasadena, California 91125, USA
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23
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Liu Y, Ma C, Shen Y, Shi J, Wang LV. Focusing light inside dynamic scattering media with millisecond digital optical phase conjugation. OPTICA 2017; 4:280-288. [PMID: 28815194 PMCID: PMC5555171 DOI: 10.1364/optica.4.000280] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Wavefront shaping based on digital optical phase conjugation (DOPC) focuses light through or inside scattering media, but the low speed of DOPC prevents it from being applied to thick, living biological tissue. Although a fast DOPC approach was recently developed, the reported single-shot wavefront measurement method does not work when the goal is to focus light inside, instead of through, highly scattering media. Here, using a ferroelectric liquid crystal based spatial light modulator, we develop a simpler but faster DOPC system that focuses light not only through, but also inside scattering media. By controlling 2.6 × 105 optical degrees of freedom, our system focused light through 3 mm thick moving chicken tissue, with a system latency of 3.0 ms. Using ultrasound-guided DOPC, along with a binary wavefront measurement method, our system focused light inside a scattering medium comprising moving tissue with a latency of 6.0 ms, which is one to two orders of magnitude shorter than those of previous digital wavefront shaping systems. Since the demonstrated speed approaches tissue decorrelation rates, this work is an important step toward in vivo deep-tissue non-invasive optical imaging, manipulation, and therapy.
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Affiliation(s)
- Yan Liu
- Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri 63130, USA
| | - Cheng Ma
- Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri 63130, USA
| | - Yuecheng Shen
- Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri 63130, USA
| | - Junhui Shi
- Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri 63130, USA
| | - Lihong V. Wang
- Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri 63130, USA
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24
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Shen Y, Liu Y, Ma C, Wang LV. Sub-Nyquist sampling boosts targeted light transport through opaque scattering media. OPTICA 2017; 4:97-102. [PMID: 28670607 PMCID: PMC5493046 DOI: 10.1364/optica.4.000097] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Optical time-reversal techniques are being actively developed to focus light through or inside opaque scattering media. When applied to biological tissue, these techniques promise to revolutionize biophotonics by enabling deep-tissue non-invasive optical imaging, optogenetics, optical tweezing, and phototherapy. In all previous optical time-reversal experiments, the scattered light field was well-sampled during wavefront measurement and wavefront reconstruction, following the Nyquist sampling criterion. Here, we overturn this conventional practice by demonstrating that even when the scattered field is under-sampled, light can still be focused through or inside scattering media. Even more surprisingly, we show both theoretically and experimentally that the focus achieved by under-sampling can be one order of magnitude brighter than that achieved under the well-sampling conditions used in previous works, where 3×3 to 5×5 pixels were used to sample one speckle grain on average. Moreover, sub-Nyquist sampling improves the signal-to-noise ratio and the collection efficiency of the scattered light. We anticipate that this newly explored under-sampling scheme will transform the understanding of optical time reversal and boost the performance of optical imaging, manipulation, and communication through opaque scattering media.
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Affiliation(s)
- Yuecheng Shen
- Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri, USA, 63130
| | - Yan Liu
- Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri, USA, 63130
| | - Cheng Ma
- Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri, USA, 63130
| | - Lihong V Wang
- Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri, USA, 63130
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25
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Koukourakis N, Fregin B, König J, Büttner L, Czarske JW. Wavefront shaping for imaging-based flow velocity measurements through distortions using a Fresnel guide star. OPTICS EXPRESS 2016; 24:22074-87. [PMID: 27661942 DOI: 10.1364/oe.24.022074] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Imaging-based flow measurement techniques, like particle image velocimetry (PIV), are vulnerable to time-varying distortions like refractive index inhomogeneities or fluctuating phase boundaries. Such distortions strongly increase the velocity error, as the position assignment of the tracer particles and the decrease of image contrast exhibit significant uncertainties. We demonstrate that wavefront shaping based on spatially distributed guide stars has the potential to significantly reduce the measurement uncertainty. Proof of concept experiments show an improvement by more than one order of magnitude. Possible applications for the wavefront shaping PIV range from measurements in jets and film flows to biomedical applications.
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26
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Shen Y, Liu Y, Ma C, Wang LV. Focusing light through biological tissue and tissue-mimicking phantoms up to 9.6 cm in thickness with digital optical phase conjugation. JOURNAL OF BIOMEDICAL OPTICS 2016; 21:85001. [PMID: 27533439 PMCID: PMC4982119 DOI: 10.1117/1.jbo.21.8.085001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 07/25/2016] [Indexed: 05/19/2023]
Abstract
Optical phase conjugation (OPC)-based wavefront shaping techniques focus light through or within scattering media, which is critically important for deep-tissue optical imaging, manipulation, and therapy. However, to date, the sample thickness in OPC experiments has been limited to only a few millimeters. Here, by using a laser with a long coherence length and an optimized digital OPC system that can safely deliver more light power, we focused 532-nm light through tissue-mimicking phantoms up to 9.6 cm thick, as well as through ex vivo chicken breast tissue up to 2.5 cm thick. Our results demonstrate that OPC can be achieved even when photons have experienced on average 1000 scattering events. The demonstrated penetration of nearly 10 cm (∼100 transport mean free paths) has never been achieved before by any optical focusing technique, and it shows the promise of OPC for deep-tissue noninvasive optical imaging, manipulation, and therapy.
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Affiliation(s)
- Yuecheng Shen
- Washington University in St. Louis, Optical Imaging Laboratory, Department of Biomedical Engineering, One Brookings Drive, St. Louis, Missouri 63130, United States
| | - Yan Liu
- Washington University in St. Louis, Optical Imaging Laboratory, Department of Biomedical Engineering, One Brookings Drive, St. Louis, Missouri 63130, United States
| | - Cheng Ma
- Washington University in St. Louis, Optical Imaging Laboratory, Department of Biomedical Engineering, One Brookings Drive, St. Louis, Missouri 63130, United States
| | - Lihong V. Wang
- Washington University in St. Louis, Optical Imaging Laboratory, Department of Biomedical Engineering, One Brookings Drive, St. Louis, Missouri 63130, United States
- Address all correspondence to: Lihong V. Wang, E-mail:
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