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TSOPC Brief
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TimeTime--Reversal Optical Phase Reversal Optical Phase Conjugation for Tissue Conjugation for Tissue Turbidity SuppressionTurbidity Suppression
Zahid Yaqoob1, Emily McDowell1, GuoanZheng1, Snow Tseng2, Michael S. Feld3,
Demetri Psaltis1,4, Changhuei Yang1
1California Institute of Technology2Taiwan National University
3MIT4EPFL
Caltech Biophotonics Laboratory
Caltech Biophotonics Laboratory
References:References:
Snow Tseng, Changhuei Yang, 2-D PSTD simulation of optical phase conjugation for turbidity suppression, OE 15, 16005 (2007)
Guoan Zheng, Lixin Ran, and Changhuei Yang, Electromagnetic equivalent model for phase conjugate mirror based on the utilization of left handed material, OE 15, 13877 (2007)
Zahid Yaqoob, Demetri Psaltis, Michael S. Feld, Changhuei Yang, Turbidity Suppression by Optical Phase Conjugation, Nature Photonics 2, 110 (2008).
A Key Difference between A Jellyfish And Me A Key Difference between A Jellyfish And Me
Caltech Biophotonics Laboratory
http://www.glaucus.org.uk/Moonjell.htm
Transparent Not Transparent!
- being transparent will really help with disease detection!
Phase Conjugation And ScatteringPhase Conjugation And Scattering
Caltech Biophotonics Laboratory
Scattering is a deterministic process. Scattering is at least 10x stronger than absorption in tissue.
At = 633nm,a photons average scattering length is 40 m.
average absorption length is 100 mm!average travel length to lose orientation is 1.2 mm
Caltech Biophotonics Laboratory
OPCWavefront
PCM
IncidentWavefront
PCM
Recording Ref Beam
Readout Ref Beam
scatterers scatterers
What is Phase Conjugation?What is Phase Conjugation?
What is Phase Conjugation?What is Phase Conjugation?
Caltech Biophotonics Laboratory
Reproduce the incident wavefront and propagate it back towards sourceEquivalently, reverses the phase wavefront.
mirrorphase conjugate mirror
http://www.futureworld.dk/tech/ether/phasecon/phasecon.htmhttp://en.wikipedia.org/wiki/Image:PhaseConjugationPrinciple.en.png
Phase Conjugation And ScatteringPhase Conjugation And Scattering
100 m
100 m
100 m
USAF target
photo-refractive crystal
USAF target 0.5 mm chicken tissue
photo-refractive crystal
USAF target clear agarose
Recording
Phase Conjugation And ScatteringPhase Conjugation And Scattering
100 m
100 m
100 m
100 m
photo-refractive crystal
photo-refractive crystal
USAF target 0.5 mm chicken tissue
USAF target clear agarose
With Chicken Breast Tissue (~ 250 With Chicken Breast Tissue (~ 250 m thick)m thick)
Caltech Biophotonics Laboratory
photo-refractive crystal
photo-refractive crystal
Some Surprising ResultsSome Surprising Results
Caltech Biophotonics Laboratory
TS-OPC reconstruction quality does not appear to deteriorate with increased scattering initially.
TS-OPC can be observed through tissues as thick as 5 mm at 532 nm wavelength
Potential ChallengesPotential Challenges
Caltech Biophotonics Laboratory
1. Living tissues will likely have micro-motions originating from cell agitations.
2. Blood flowDoes indeed impact on TSOPC, but deterioration rate is measured to be ~ 10s seconds.
We lose light trajectories that pass through blood, but TSOPC does not require complete wavefrontreplication.
Both are non-issues if we employ real-time optical phase conjugation approaches.
Examples: 4-wave mixing, 2D phase modulator + wavefront sensor
What is this phenomenon good for?What is this phenomenon good for?
Caltech Biophotonics Laboratory
photorefractive crystal
Probably not a good idea.
1. A means for targeting strong 1. A means for targeting strong scatterersscatterers in in tissuetissue
Caltech Biophotonics Laboratory
photorefractive crystal
photorefractive crystal
Step 1: Send in weak illumination
photorefractive crystal
Step 2: Record the backscattering
Step 3: Play back the PC wavefront
Good for:
1. Photodynamic Therapy2. Neuron Activation3. Port-wine Stain Removal4. Basically any situation where you
want to concentrate light on strong scatterers in tissue.
absorbing dyemolecules
strongscatterer
Caltech Biophotonics Laboratory
forward illumination
transmission
side scatter
back scatter
forward illumination
transmission
side scatter
back scatter
A
B
2. A means for measuring scattering site 2. A means for measuring scattering site heterogeneityheterogeneity
3. Deep tissue imaging (separation of 3. Deep tissue imaging (separation of absorption and scattering contributions)absorption and scattering contributions)
Caltech Biophotonics Laboratory
BiologicalSample
PCM1
(a)
BiologicalSample
PCM1
(b)
BiologicalSample
PCM1
(c)
PCM2 PCM2
brown = absorptive objects
Caltech Biophotonics Laboratory
References:References:
Snow Tseng, Changhuei Yang, 2-D PSTD simulation of optical phase conjugation for turbidity suppression, OE 15, 16005 (2007)
Guoan Zheng, Lixin Ran, and Changhuei Yang, Electromagnetic equivalent model for phase conjugate mirror based on the utilization of left handed material, OE 15, 13877 (2007)
Zahid Yaqoob, Demetri Psaltis, Michael S. Feld, Changhuei Yang, Turbidity Suppression by Optical Phase Conjugation, Nature Photonics 2, 110 (2008).