Matched pulse stimulated raman scattering
AssigneeThe Board of Trustees of the University of Illinois
InventorsDaniel L. Marks, Joseph B. Geddes, III, Stephen A. Boppart
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Abstract
Methods and apparatus for selectively driving the vibrations of normal modes of a target molecule into coherence using stimulated Raman scattering. In concert, many vibrations produce a larger anti-Stokes signal than a single vibration. The same illumination does not drive other molecules to have coherent vibrations, so these molecules produce a weaker signal. Target and confounder molecules can be distinguished by pulses that drive many vibrations coherently, with applications in coherent Raman microspectroscopy.
Claims20
A method for identifying the presence of a target molecular species in a sample, the molecular species characterized by a plurality of vibrational modes and a Raman impulse response, the method comprising:
- a. defining at least one feature of an exciting electromagnetic pulse on a basis of features of the Raman impulse response of the target species;
- b. exciting the sample with the electromagnetic pulse;
- c. generating coherent stimulated scattered radiation;
- d. interfering the coherent stimulated radiation with a reference pulse so as to cross-correlate the coherent stimulated radiation and the reference pulse, the reference pulse characterized by a relative timing with respect to the exciting electromagnetic radiation;
- e. shaping the reference pulse for selectively enhancing a correlation with scatter of the target species;
- f. sweeping the delay time so as to measure correlation as a function of delay time;
- and
- g. determining the presence of the target species based at least on a specified criterion applied to correlation as a function of delay time.
An apparatus for identifying the presence of a target molecular species in a sample, the apparatus comprising:
- a. a source of ultrashort electromagnetic pulses;
- b. a pulse shaper for shaping pulses generated by the source in a manner exhibiting target species specificity;
- c. an interferometer for interfering pulses traversing a sample with reference pulses traversing a reference path;
- d. at least one detector for detecting a combination of pulses traversing the sample with reference pulses traversing the reference path;
- e. a correlator for determining the presence of the target species based at least on a specified criterion applied to correlation as a function of delay time;
- and
- f. a target sample disposed within the reference path.
Dependencies are inferred from the claim text.