US 10,031,424 B2Granted

Fabrication of high efficiency, high quality, large area diffractive waveplates and arrays

AssigneesBeam Engineering for Advanced Measurements Co., The United States of America as represented by the Secretary of the Army

InventorsNelson V. Tabirian, Sarik R. Nersisyan, Brian R. Kimball, Diane M. Steeves

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Abstract

The objective of the present invention is providing a method for fabricating high quality diffractive waveplates and their arrays that exhibit high diffraction efficiency over large area, the method being capable of inexpensive large volume production. The method uses a polarization converter for converting the polarization of generally non-monochromatic and partially coherent input light beam into a pattern of periodic spatial modulation at the output of said polarization converter. A substrate carrying a photoalignment layer is exposed to said polarization modulation pattern and is coated subsequently with a liquid crystalline material. The high quality diffractive waveplates of the present invention are obtained when the exposure time of said photoalignment layer exceeds by generally an order of magnitude the time period that would be sufficient for producing homogeneous orientation of liquid crystalline materials brought in contact with said photoalignment layer. Compared to holographic techniques, the method is robust with respect to mechanical noises, ambient conditions, and allows inexpensive production via printing while also allowing to double the spatial frequency of optical axis modulation of diffractive waveplates.

Claims10

Dependent claims

A method for producing orientation modulation of an anisotropy axis of a photoresponsive material layer at a predetermined spatial period, the method comprising:

(a) emitting a light beam being at least partially coherent and having a linear polarization from a light source;
(b) using a polarization converter to periodically modulate in space the polarization of said light beam, the polarization converter having an optical axis modulation period that is twice larger than said predetermined spatial period, said polarization converter comprising at least one diffractive waveplate that is achromatic and is part of an array of diffractive waveplates, and provides diffraction efficiency greater than 95% over an area of greater than 1″ in diameter, and scattering losses less than 1%;
(c) providing a photoresponsive material layer having an absorption spectrum that comprises wavelengths of said light beam, and having an anisotropy axis that is formed according to polarization of said light beam;
and
(d) exposing at least a portion of said photoresponsive material layer by projecting a polarization modulation pattern produced by said polarization converter at an exposure energy density optimized for producing alignment of the anisotropy axis of the photoresponsive material layer at a predetermined spatial period without causing degradation of the photoresponsive material layer, said exposure energy density exceeding at least 5 times the exposure energy density sufficient for producing waveplates with homogeneous orientation of the optical axis whereby a sole result of exposing the photoresponsive material layer to the polarization modulation pattern is the alignment of the anisotropy axis in said photoresponsive material according to the polarization modulation pattern.

2 more elements

An apparatus for producing spatially periodic orientation modulation of an anisotropy axis of a photoresponsive material layer at a predetermined spatial period, the apparatus comprising:

(a) a light source emitting a linearly polarized light beam that is at least partially coherent;
(b) a polarization converter configured to periodically modulate the polarization of said light beam along a single axis to generate a polarization modulation pattern, the polarization converter having an optical axis modulation period that is twice larger than the predetermined spatial period of said spatially periodic orientation modulation of anisotropy axis of the photoresponsive material layer, said polarization converter comprises at least one diffractive waveplate that is achromatic and is part of an array of diffractive waveplates and provides diffraction efficiency greater than 95% over an area greater than 1″ in diameter, and scattering losses less than 1%;
(c) a photoresponsive material having an absorption spectrum that comprises wavelengths of said light beam and an anisotropy axis that is formed or aligned according to polarization of said light beam;
(d) means for holding and positioning a layer of said photoresponsive material;
(e) means for positioning and projecting the polarization modulation pattern onto at least a portion of said photoresponsive material layer;
(f) means for exposing different areas of said photoresponsive material layer to said polarization modulation pattern at an exposure energy density optimized for producing alignment of the anisotropy axis of the photoresponsive material layer at a predetermined spatial period without causing degradation of said photoresponsive material, said exposure energy density exceeding at least 5 times the exposure energy density sufficient for producing waveplates with homogeneous orientation of the optical axis whereby solely the anisotropy axis in said photoresponsive material is aligned according to the polarization modulation pattern of the polarization converter.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application: 14/810,569Filed 28 Jul 2015 · continuation
Priority: 21 Apr 2010
Published: US 2016/0026092 A128 Jan 2016
Granted: 24 Jul 2018
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

G03F 7/70191
Mask illumination systems: optical correction elements, filters or phase plates for controlling intensity, wavelength, polarisation, phase or the like
G02B 5/3083
Polarising elements: birefringent or phase retarding elements
G02B 5/32
Optical elements other than lenses: holograms used as optical elements
G03F 7/20
Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g.…

Family

Application12/662,525Parent of this continuation · filed 21 Apr 2010
Application13/860,934Parent of this continuation · filed 11 Apr 2013
US 2016/0026092 A1Pre-grant publication · published 28 Jan 2016
US 2011/0262844 A1Published application
US 2013/0236817 A1Published application
US 10,031,424 B2This patent

From the US filing history. Foreign family members aren’t listed.