Diffraction grating with reduced polarization sensitivity
AssigneeCorning Incorporated
InventorDipakbin Qasem Chowdhury
Life of this patent
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Abstract
A multiplexer/demultiplexer for routing different wavelength signals between a common pathway for conveying a plurality of the signals, and individual pathways for separately conveying the signals includes a reflective diffraction grating with reduced polarization sensitivity for dispersing the signals. The grating includes facets that are oriented for reducing efficiency variations within a transmission bandwidth and that are shaped for reducing differences between the diffraction efficiencies in two orthogonal directions of differentiation.
Claims2
An optical device for routing different wavelength signals within a transmission bandwidth ".DELTA..lambda." comprising:
- a common pathway for conveying a plurality of the different wavelength signals;
- individual pathways for separately conveying the different wavelength signals;
- a diffraction grating interconnecting said common and individual pathways with a first diffraction efficiency in one of two orthogonal directions of polarization and a second diffraction efficiency in the other orthogonal direction of polarization;
- said first and second diffraction efficiencies varying as a function of wavelength within the transmission bandwidth ".DELTA..lambda." between maximum and minimum values having a difference ".DELTA.E.sub.max ";
- said first and second diffraction efficiencies differing from each other at corresponding wavelengths through a maximum difference ".DELTA.P.sub.max ";
- and
- said reflective diffraction grating including reflective faces that are oriented for balancing the differences ".DELTA.E.sub.max " in both directions of polarization and that are shaped for minimizing the difference ".DELTA.P.sub.max " between the directions of polarization.
A method of making an optical device that routes different wavelength optical signals of unpolarized light between a common pathway that conveys a plurality of the different wavelength signals and individual pathways that separately convey the different wavelength signals comprising the steps of:
- interconnecting the common and individual pathways with a diffraction grating exhibiting a first diffraction efficiency in one of two orthogonal directions of polarization and a second diffraction efficiency in the other orthogonal direction of polarization;
- forming the diffraction grating with a plurality of reflective faces joined by side walls;
- arranging the reflective faces for converting an angular dispersion of the different wavelength signals into a predetermined linear dispersion of the different wavelength signals along a focal line;
- aligning inner ends of the individual pathways along the focal line for receiving the different wavelength signals;
- joining a first end of the reflective faces to the side walls with rounded corners having convex reflective profiles;
- joining a second end of the reflective faces to the side walls with rounded corners having concave reflective profiles;
- and
- sizing the rounded corners having the concave reflective profiles for minimizing differences between the diffraction efficiencies in the two orthogonal directions of polarization.
Dependencies are inferred from the claim text.