Diffraction grating with reduced polarization sensitivity

• US 6,097,863 A
• Filed: 06/07/1999
• Issued: 08/01/2000
• Est. Priority Date: 07/02/1996
• Status: Expired due to Term

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Chowdhury, Dipakbin Qasem
• Primary Examiner(s): Ullah, Akm E.
• Application Number:
  US09/326,310
• Time in Patent Office: 421 Days
• Field of Search: 385/37, 385/31, 385/47, 359/566, 359/618
• US Class Current: 385/37
• CPC Class Codes: G02B 2006/12107 Grating
• CPC Class Codes: G02B 5/1809 with pitch less than or comparable to the wavelength
• CPC Class Codes: G02B 5/1861 Reflection gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• CPC Class Codes: G02B 6/124 Geodesic lenses or integrated gratings
• CPC Class Codes: G02B 6/29307 components assembled in or forming a solid transparent unitary block, e.g. for facilitating component alignment
• CPC Class Codes: G02B 6/29308 Diffractive element having focusing properties, e.g. curved gratings Rowland circle spectrometers G01J3/20
• CPC Class Codes: G02B 6/29326 Diffractive elements having focusing properties, e.g. curved gratings Rowland circle spectrometers G01J3/20
• CPC Class Codes: G02B 6/29328 Diffractive elements operating in reflection

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.

Claims

1. An optical device for routing different wavelength signals within a transmission bandwidth "Δ

λ

" 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 "Δ

λ

" between maximum and minimum values having a difference "Δ

E_max ";

said first and second diffraction efficiencies differing from each other at corresponding wavelengths through a maximum difference "Δ

P_max "; and

said reflective diffraction grating including reflective faces that are oriented for balancing the differences "Δ

E_max " in both directions of polarization and that are shaped for minimizing the difference "Δ

P_max " between the directions of polarization.

2. 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.