Time-Reversed Ultrasonically Encoded (TRUE) optical focusing in reflection mode: Demonstrations in tissue mimicking phantoms and ex vivo tissue

Puxiang Lai, Xiao Xu, Honglin Liu, Yuta Suzuki, Lihong V. Wang

Research output: Chapter in book / Conference proceedingConference article published in proceeding or bookAcademic researchpeer-review

1 Citation (Scopus)


The problem of how to effectively deliver light dynamically to a small volume inside turbid media has been intensively investigated for imaging and therapeutic purposes. Most recently, a new modality termed Time-Reversed Ultrasonically Encoded (TRUE) optical focusing was proposed by integrating the concepts of ultrasound modulation of diffused light with optical phase conjugation. In this work, the diffused photons that travel through the ultrasound focal region are "tagged" with a frequency shift due to the ultrasound modulation. Part of the tagged light is collected in reflection mode and transmitted to a photorefractive crystal, forming there a stationary hologram through interference with a coherent reference optical beam. The hologram is later read by a conjugated optical beam, generating a phase conjugated wavefront of the tagged light. It is conveyed back to the turbid medium in reflection mode, and eventually converges to the ultrasound focal zone. Optical focusing effects from this system are demonstrated experimentally in tissue-mimicking phantoms and ex vivo chicken breast tissue, achieving effective round-trip optical penetration pathlength (extinction coefficient multiplied by round-trip focusing depth) exceeding 160 and 100, respectively. Examples of imaging optical inclusions with this system are also reported.
Original languageEnglish
Title of host publicationPhotons Plus Ultrasound
Subtitle of host publicationImaging and Sensing 2012
Publication statusPublished - 9 Apr 2012
Externally publishedYes
EventPhotons Plus Ultrasound: Imaging and Sensing 2012 - San Francisco, CA, United States
Duration: 22 Jan 201224 Jan 2012


ConferencePhotons Plus Ultrasound: Imaging and Sensing 2012
Country/TerritoryUnited States
CitySan Francisco, CA


  • Biological tissue
  • Optical fiber bundle
  • Optical focusing
  • Optical imaging
  • Optical phase conjugation
  • Phase conjugation mirror
  • Photorefractive crystal
  • Reflection mode
  • Time reversal
  • Tissue-mimicking phantom
  • Ultrasound modulation

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Radiology Nuclear Medicine and imaging


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