Method for fixing optical information in crystals and for quasi-phase matching in frequency mixing
AssigneeTechnion Research & Development Foundation Limited
InventorsBaruch Fischer, Moshe Horowitz
Life of this patent
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Abstract
A method and apparatus for fixing images, holograms and domain gratings in crystals by application of an electric field on a crystal and simultaneous illumination of it with a light pattern. The fixing procedure is based on a screening effect. The modulation of the domains may be perpendicular to the c-axis. Another application of the method is in frequency mixing such as second harmonic generation and parametric processes, by overcoming the problem of phase matching using the domain gratings. Thus, it is possible to obtain controllable broadband mixing and tailored quasi-phase matching for several wavelengths or for prespecified wavelength tuning ranges and frequency widths.
Claims16
A method for reversibly fixing optical images and holograms in a crystal having a predefined polarization, said method comprising the steps of:
- projecting on the crystal a first input light pattern comprising an image or hologram having grating vectors which are substantially perpendicular to the ferroelectric polarization direction of the crystal, said image or hologram having interference fringe planes which are substantially parallel to said ferroelectric polarization direction;
- applying, simultaneous with said projecting step, a voltage to the crystal along said polarization direction thereof, to induce an internal electric field pattern therein;
- blocking said first input light pattern;
- and
- applying a second voltage with polarity opposite to said voltage,
- such that ferroelectric domains are induced with a modulation direction substantially perpendicular to said polarization direction to provide transverse domain gratings, and said first input light pattern is permanently fixed in said crystal until erased by application of an electric field thereto simultaneous with a second input light pattern.
A method for reversibly fixing optical images and holograms in a crystal having a predefined polarization, said method comprising the steps of:
- projecting on the crystal a first input light pattern comprising an image or hologram, wherein said first input light pattern has a modulation direction perpendicular to the ferroelectric polarization direction of the crystal;
- applying, simultaneous with said projecting step, a voltage to the crystal along said polarization direction thereof, to induce an internal electric field pattern therein;
- blocking said first input light pattern;
- and
- applying a second voltage with polarity opposite to said voltage,
- such that transverse ferroelectric domain gratings are induced in the crystal and said first input light pattern is permanently fixed in said crystal until erased by application of an electric field thereto simultaneous with a second input light pattern.
Dependencies are inferred from the claim text.