Electro-optical and magneto-optical sensing apparatus and method for characterizing free-space electromagnetic radiation
AssigneeRensselaer Polytechnic Institute
InventorsXi-Cheng Zhang, Jenifer Ann Riordan, Feng-Guo Sun
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Abstract
Apparatus and methods for characterizing free-space electromagnetic energy, and in particular, apparatus/method suitable for real-time two-dimensional far-infrared imaging applications are presented. The sensing technique is based on a non-linear coupling between a low-frequency electric (or magnetic) field and a laser beam in an electro-optic (or magnetic-optic) crystal. In addition to a practical counter-propagating sensing technique, a co-linear approach is described which provides longer radiated field-optical beam interaction length, thereby making imaging applications practical.
Claims20
A magneto-optical sensor for characterizing a free-space magnetic field, said magneto-optical sensor comprising:
- means for generating said free-space magnetic field, said means for generating comprising a pump and an emitter, said pump comprising a pulsed laser which outputs an optical pulse to said emitter, said emitter responding thereto by outputting said free-space magnetic field;
- a magneto-optic crystal positionable so that the free-space magnetic field passes therethrough, thereby changing an index of refraction thereof;
- means for generating an optical probe signal to impinge the magneto-optic crystal simultaneous with the free-space magnetic field passing therethrough;
- sensing means for determining ellipticity modulation of the optical probe signal after impinging upon the magneto-optic crystal;
- and
- means for characterizing the free-space magnetic field by evaluating the ellipticity modulation of the optical probe signal.
Apparatus for characterizing magnetic components of free-space radiation, said apparatus comprising:
- means for generating said free-space radiation, said means for generating comprising a pump and an emitter, said pump comprising a pulsed laser which outputs an optical pulse to said emitter, said emitter responding thereto by outputting said free-space radiation;
- a magneto-optic crystal positionable so that at least a portion of the free-space radiation passes therethrough, said magneto-optic crystal having an index of refraction and a polarization changed by the free-space radiation passing therethrough in accordance with Faraday's effect;
- means for generating a polarized optical probe signal oriented to refract with said magneto-optic crystal simultaneous with said free space radiation passing therethrough, said optical probe signal optically sampling said change in the index of refraction and the polarization of the magneto-optic crystal;
- and
- means for processing said optical sample to characterize the magnetic components of the free-space radiation using the change in the index of refraction and the polarization of the magneto-optic crystal.
An imaging system for imaging an object, said imaging system comprising:
- means for generating a free-space radiation beam having a magnetic component, said free-space radiation beam being positionable to pass through the object to be imaged, said means for generating comprising a pump and an emitter, said pump comprising a pulsed laser which outputs an optical pulse to said emitter, said emitter responding thereto by outputting said free-space radiation beam;
- a magneto-optic crystal positionable so that the radiation beam passes through the magneto-optic crystal after passing through the object, said radiation beam changing the index of refraction of said magneto-optic crystal;
- means for generating an optical probe signal to impinge the magneto-optic crystal simultaneous with the radiation beam passing therethrough;
- sensing means for determining ellipticity modulation of the optical probe signal after impinging upon the magneto-optic crystal;
- means for evaluating the ellipticity modulation of the optical probe signal to characterize the magnetic component of the radiation beam;
- and
- means for displaying an image of the said object using said characterization of said magnetic component of the radiation beam.
Dependencies are inferred from the claim text.