Interferometric optical fiber

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Transcript of Interferometric optical fiber

Microsoft PowerPoint - Interferometric optical fiber biosensor.ppt [Compatibility Mode]1
Fiber probe design
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Interferometer • Interference usually refers to the interaction of
waves that are correlated or coherent with each other – either because they come from the same source – or because they have the same or nearly the same
frequency.
• Two waves that coincide with the same phase will add to each other.
• Two waves that have opposite phases will cancel each other out, assuming both have the same amplitude.
5http://en.wikipedia.org/wiki/Interferometer
Constructive and destructive condition
• If these two paths differ by a whole number (including 0) of wavelengths, there is constructive interference and a strong signal at the detector.
• If they differ by a whole number and a half wavelengths (e.g., 0.5, 1.5, 2.5 ...) there is destructive interference and a weak signal.
• Violate conservation of energy?
Constructive and destructive condition
• If these two paths differ by a whole number (including 0) of wavelengths, there is constructive interference and a strong signal at the detector.
• If they differ by a whole number and a half wavelengths (e.g., 0.5, 1.5, 2.5 ...) there is destructive interference and a weak signal.
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Constructive and destructive condition
• If these two paths differ by a whole number (including 0) of wavelengths, there is constructive interference and a strong signal at the detector.
• If they differ by a whole number and a half wavelengths (e.g., 0.5, 1.5, 2.5 ...) there is destructive interference and a weak signal.
• Violate conservation of energy?
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How does it work?
• A slight tilt of one of the beam splitters will result in a path difference and a change in the interference pattern.
• Can be very difficult to align. • Very sensitive.
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Advantages: very sensitive
• Coherent interferometry uses a coherent light source (for example, a helium-neon laser), and can make interference with large difference between the interferometer path length delays.
• The interference is capable of very accurate (nanometer) measurement by recovering the phase.
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– Coherent interferometry suffers from a 2π ambiguity problem
– If between any two measurements the interferometric phase jumps by more than 2π the phase measurement is incorrect
– Dynamic range
– Coherent interferometry suffers from a 2π ambiguity problem
– If between any two measurements the interferometric phase jumps by more than 2π the phase measurement is incorrect
– Dynamic range
• Combining interferometry results obtained using multiple wavelengths of illumination
• Ambiguity interval can be extended to indefinitely large dynamic ranges of measurement
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• Long (typically 9–20 mm) evanescent- wave/biomaterial interaction paths
• Required length for a detectable cumulative effect when using a single pass of light through the sensing arm
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• Long (typically 9–20 mm) evanescent- wave/biomaterial interaction paths
• Required length for a detectable cumulative effect when using a single pass of light through the sensing arm
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EFPI
• The required sensing length may be reduced by having the light double back through multiple reflections along its propagation path.
• The use of a single-cavity extrinsic Fabry– Pérot interferometer (EFPI) as a guided- wave/bulk-biomaterial interaction biosensor.
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J. L. Elster, M. E. Jones, M. K. Evans, S. M. Lenahan, C. A. Boyce, W. Velander, and R. VanTassell, “Optical fiber extrinsic Fabry–Pérot interferometric (EFPI)-based biosensors,” SPIE, vol. 3911, pp. 105–112,2000.
Fabry Perot Interferometer
• http://www.youtube.com/watch?v=BT675F huvuA
Schematic diagram of a PSW- FPI integrated in a uMZ
structure
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Diffraction
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Comparable in size to the wavelength Light spreads around the edges of the obstacle
Single slit diffraction
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Analysis
• Huygen's principle – Each part of the slit can be thought of as an
emitter of waves. – All these waves interfere to produce the
diffraction pattern.
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Results
• Destructive interference: 1-5; 2-6; 3-7; 4-8… • Half a wavelength out of phase
– (w/2)sinθ = λ/2 or wsinθ = λ • Other dark fringes in the diffraction pattern produced
are found at angles θ for which – wsinθ = mλ
• If the interference pattern is viewed on a screen a distance L from the slits, then the wavelength can be found from the spacing of the fringes. – λ = zw/(mL)
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Results
• Destructive interference: 1-5; 2-6; 3-7; 4-8… • Half a wavelength out of phase
– (w/2)sinθ = λ/2 or wsinθ = λ • Other dark fringes in the diffraction pattern produced
are found at angles θ for which – wsinθ = mλ
• If the interference pattern is viewed on a screen a distance L from the slits, then the wavelength can be found from the spacing of the fringes. – λ = zw/(mL)
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Exercise 1
• When a monochromatic light source shines through a 0.2mm wide slit onto a screen 3.5m away, the first dark band in the pattern appears 9.1mm from the center of the bright band. What is the wavelength of the light?
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Exercise 2
• The first order bright line appears 0.25cm from the center bright line when a double slit grating is used. The distance between the slits is 0.5mm and the screen is 2.7m from the grating. Find the wavelength.
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Exercise 3
• A diffraction grating has 420 lines per mm. The grating is used to observe light with a wavelength of 440nm. The grating is placed 1.3m from the source. Where will the first order bright line appear?
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Solution 3
• Lamda=wsin • w=1/420=2.38um • Lamda=440nm • L=1.3m • Z=Ltan~ 24.5cm
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• Identical, equally-space slits? • The bright fringes, which come from
constructive interference of the light waves from different slits, are found at the same angles they are found if there are only two slits.
• But the pattern is much sharper. • Why?
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Diffraction grating
• Each scattering center acts as a point source of spherical wavefronts;
• These wavefronts undergo constructive interference to form a number of diffracted beams.
• Many positions of completely destructive interference between the bright, constructive-interference fringes.
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biochemical assay technique • A guided mode resonance filter that, • when illuminated with white light, • is designed to reflect only a narrow band
of wavelengths • where the reflected wavelength is tuned by
the adsorption of biological material onto the sensor surface.
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Label-free
• Label-free – removes experimental uncertainty induced by the effect of
• the label on molecular conformation, • blocking of active binding epitopes, • steric hindrance, • inaccessibility of the labeling site, • or the inability to find an appropriate label that functions
equivalently for all molecules in an experiment. – Label-free detection methods greatly simplify the time and
effort required for assay development, • Removing experimental artifacts from quenching, shelf life,
and background fluorescence.
• A narrow bandwidth guided mode resonant filter structure – a sub-wavelength grating structure – produces a particular diffraction anomaly providing a surface
that, – when illuminated with white light at normal incidence, – reflects only a very narrow (resonant) band of wavelengths.
• The resonantly reflected wavelength is shifted by the attachment of biomolecules to the guided mode filter, – small changes in surface optical density can be quantified
• Equivalent sensor structures have been fabricated onto glass substrates and incorporated into sheets of plastic film.
• Incorporation of the sensor into large area disposable assay formats such as microtiter plates and microarray slides.
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Sensitivity
sensitivity • Low non-specific binding
binding of molecules
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binding of molecules
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Test
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Imaging
• To produce images of bound biomolecule patterns as applied by a microarray spotter
• An instrument is used to acquire spatial maps of the resonant reflected wavelength
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Applications
• The biosensor imaging capability is expected to yield applications in pharmaceutical compound screening, genomics, proteomics, and molecular diagnostics,
• where there is a need to screen large numbers of biochemical interactions against samples
• using low volumes of reagents. 61
Parallel detection with an array
• The ability to detect the interactions between sets of DNA probes arrayed on to glass surfaces and test samples are used for genotyping, gene expression analysis, and gene sequencing.
• Likewise, arrays of hybridized protein probes are finding applications in protein pathway analysis, and protein expression diagnostic tests.
• The concept of parallel detection of sample interaction with an array of hybridized probes is further expanding into
• Small molecule screening for pharmaceutical discovery • Environmental testing, and others.
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Advantages
• Low cost • Multi-analyte analysis in parallel • Simple setup – no coupling prisms • No electricity wiring
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Video
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References
• Optical fiber extrinsic Fabry–Pérot interferometric (EFPI)-based biosensors J. L. Elster, M. E. Jones, M. K. Evans, S. M. Lenahan, C. A. Boyce, W. Velander, and R. VanTassell SPIE, vol. 3911, pp. 105–112,2000.
• Investigation of a Periodically Segmented Waveguide Fabry–PÉrot Interferometer for Use as a Chemical/Biosensor N Kinrot, M Nathan Journal of Lightwave Technology, Volume 24, Number 5 (May 2006) Page Numbers: 2139 - 2145
• Label-free optical technique for detecting small molecule interactions Bo Lin, Jean Qiu, John Gerstenmeier, Peter Li, Homer Pien, Jane Pepper and Brian Cunningham Biosensors and Bioelectronics, Volume 17, Issue 9, September 2002, Pages 827-834
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References
• A new method for label-free imaging of biomolecular interactions Li, P.Y.; Bo Lin; Gerstenmaier, J.; Cunningham, B.T.; Sensors, 2003. Proceedings of IEEE Volume 1, 22-24 Oct. 2003 Page(s):310 - 315 Vol.1 Digital Object Identifier 10.1109/ICSENS.2003.1278948
• A plastic colorimetric resonant optical biosensor for multiparallel detection of label-free biochemical interactions Cunningham, B.; Qiu, J.; Lin, B.; Li, P.; Pepper, J.; Sensors, 2002. Proceedings of IEEE Volume 1, 12-14 June 2002 Page(s):212 - 216 vol.1 Digital Object Identifier 10.1109/ICSENS.2002.1037084
• Colorimetric resonant reflection as a direct biochemical assay technique Brian Cunningham, Peter Li, Bo Lin and Jane Pepper
Sensors and Actuators B: Chemical, Volume 81, Issues 2-3, 5 January 2002, Pages 316-328
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