Claims
- 1. An optical surface grating device having a diffraction efficiency substantially independent of a light polarization direction over a preselected wavelength range comprising:
at least one first grating element having a diffraction efficiency, a grating period and a first height defining a modulation depth of a first grating relief pattern, and at least one second grating element having the grating period, and a diffraction efficiency and a second height defining a modulation depth of a second grating relief pattern, with the second height being different from the first height, wherein the at least one first and second grating elements are arranged substantially side-by-side to form the optical surface grating device and the first height and the second height are selected so that an average value formed from the diffraction efficiencies of the first and second grating elements over the preselected wavelength range is substantially identical for two orthogonal polarization directions.
- 2. The grating device of claim 1, wherein the average value is weighted according to a ratio of surface areas of the first and second grating elements exposed to optical radiation illuminating the grating device.
- 3. The grating device of claim 1, wherein the first height and the second height are selected so that a slope of the diffraction efficiency of the first grating element as a function of wavelength over the predetermined wavelength range is opposite in sign from a slope of the diffraction efficiency of the second grating element over the predetermined wavelength range, so as to provide a substantially wavelength-independent diffraction efficiency of the grating device.
- 4. The grating device of claim 1, wherein the grating elements are ruled gratings or etched gratings.
- 5. The grating device of claim 4, wherein the respective heights of the first and second grating relief patterns define respective blaze angles.
- 6. The grating device of claim 1, wherein the grating elements are holographic gratings.
- 7. The grating device of claim 1, wherein the first and second grating elements are arranged in a geometrical pattern on a common surface.
- 8. The grating device of claim 7, wherein the geometrical pattern is a checkerboard pattern.
- 9. The grating device of claim 7, wherein the geometrical pattern is a stripe pattern.
- 10. The grating device of claim 9, wherein the first an second grating relief patterns are in the form of linear stripes and the linear stripes are arranged to be parallel to the stripe pattern.
- 11. The grating device of claim 9, wherein the first an second grating relief patterns are in the form of linear stripes and the linear stripes are arranged to be at a non-zero angle with respect to the stripe pattern.
- 12. The grating device of claim 7, wherein the common surface is one of planar or curved.
- 13. The grating device of claim 1, wherein the first and second grating elements are arranged side-by-side and an area where the first and second grating elements are joined is apodized.
- 14. An optical wavelength division demultiplexer having a substantially polarization-independent response over a predetermined wavelength range, comprising:
at least one optical illumination source, a grating device receiving optical radiation from the illumination source, the grating device including
at least one first grating element having a grating period and a first height defining a modulation depth of a first grating pattern, at least one second grating element having the grating period and a second height defining a modulation depth of a second grating relief pattern, with the second height being different from the first height, and a plurality of optical receiving devices receiving wavelength-selected diffracted optical radiation from the grating device, wherein the first and second grating elements are arranged substantially side-by-side to form the optical surface grating and the first height and the second height are selected so that an average value formed from the diffraction efficiencies of the first and second grating elements over the preselected wavelength range is substantially identical for two orthogonal polarization directions and an intensity of the wavelength-selected diffracted optical radiation is substantially independent of a direction of polarization of the at least one optical illumination source.
- 15. An optical wavelength division multiplexer having a substantially polarization-independent response over a predetermined wavelength range, comprising:
a plurality of optical illumination sources, a grating device receiving optical radiation from the illumination sources, the grating device including
at least one first grating element having a grating period and a first height defining a modulation depth of a first grating relief pattern, at least one second grating element having the grating period and a second height defining a modulation depth of a second grating relief pattern, with the second height being different from the first height, and at least one optical receiving device receiving wavelength-combined diffracted optical radiation from the grating device, wherein the first and second grating elements are arranged substantially side-by-side to form the optical surface grating and the first height and the second height are selected so that an average value formed from the diffraction efficiencies of the first and second grating elements over the preselected wavelength range is substantially identical for two orthogonal polarization directions, and an intensity of the wavelength-combined diffracted optical radiation is substantially independent of a direction of polarization of the plurality of optical illumination sources.
- 16. A method of producing diffracted optical radiation that is substantially independent of a polarization direction of illuminating optical radiation over a preselected wavelength range, comprising:
diffracting a first portion of the illuminating optical radiation on at least one first grating element having a grating period and a first height defining a modulation depth of a first grating relief pattern, diffracting a second portion of the illuminating optical radiation on at least one second grating element having the grating period and a second height different from the first height, with the second height defining a modulation depth of a second grating relief pattern, and combining the diffracted first and second portions to form the diffracted optical radiation, wherein the first height and the second height, and the first portion and the second portion, respectively, are selected so that an average value formed from the diffraction efficiencies of the first and second grating elements over the preselected wavelength range is substantially identical for two orthogonal polarization directions.
- 17. The method of claim 16, wherein the first height and the second height are selected so that a slope of a diffraction efficiency of the first grating element as a function of wavelength over the predetermined wavelength range is opposite in sign from a slope of a diffraction efficiency of the second grating element over the predetermined wavelength range, so that an average value formed from the diffraction efficiencies of the first and second grating elements over the preselected wavelength range is substantially independent of wavelength.
CROSS-REFERENCE TO OTHER PATENT APPLICATIONS
[0001] This application claims the benefit of U.S. provisional Patent Application No. 60/192,396, filed Mar. 27, 2000.
Provisional Applications (1)
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Number |
Date |
Country |
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60192396 |
Mar 2000 |
US |