Partially etched phase-transforming optical element

Patent metadata

Field	Value
Publication number	US-2016306167-A1
Application number	US-201514687882-A
Country	US
Kind code	A1
Filing date	Apr 15, 2015
Priority date	Apr 15, 2015
Publication date	Oct 20, 2016
Grant date	—

Abstract

A optical element (transmissive or reflective) includes a transmissive layer comprising two different optical media arranged among discrete volumes arranged along the layer. The discrete volumes are arranged to approximate a desired phase function (typically modulo 2π) and are smaller than an operational wavelength in order to provide a range of phase delays needed to adequately approximate the desired phase function.

First claim

What is claimed is:

1 . An optical element comprising a transmissive layer comprising first and second optical media, wherein:
(a) the first and second optical media are substantially transparent over an operational wavelength range including a design vacuum wavelength λ 0 and are characterized by differing respective first and second wavelength-dependent bulk refractive indices n 1 (λ) and n 2 (λ), and the first optical medium comprises a substantially solid material; (b) the first and second optical media are arranged within the layer as a contiguous multitude of discrete volumes, including a subset of volumes of the multitude having a largest transverse dimension less than about λ 0 , wherein each discrete volume comprises either the first optical medium or the second optical medium, but not both; (c) the contiguous multitude of discrete volumes is arranged so that (i) any given simply connected sample volume of the transmissive layer, said sample volume having transverse dimensions about equal to λ 0 and extending from the first surface through the transmissive layer to a second surface of the transmissive layer, includes only the first optical medium, only the second optical medium, or both the first and second optical media of at least portions of two or more of the discrete volumes, and (ii) any straight-line path, extending substantially perpendicularly from a first surface of the transmissive layer to a second surface of the transmissive layer, passes through only the first optical medium, through only the second optical medium, or through only one discrete volume of each of the first and second optical media; (d) the discrete volumes of the multitude are distributed on the transmissive layer so that (2π/λ 0 )·(n 1 (λ 0 )·d 1 (x,y)+n 2 (λ 0 )·d 2 (x,y)), as a function of two-dimensional position coordinates x and y along the first surface of the transmissive layer, averaged over a sampling area having a largest transverse dimension about equal to λ 0 along the first surface of the transmissive layer, is substantially equal to a specified position-dependent effective phase transformation function φ eff (x,y), or substantially equal to ½·φ eff (x,y), where (i) d 1 (x,y) and d 2 (x,y) are the respective local distances through the first and second optical media along the straight-line path through a given position (x,y), and (ii) φ eff (x,y) varies with both x and y; and (e) the optical element is structurally arranged to as to receive an optical signal incident on the first surface within the transmission region and to transmit or reflect at least a portion of the incident optical signal transformed substantially according to the effective phase transformation function φ eff (x,y).

2 . A method employing the optical element of claim 1 , the method comprising (i) directing an optical signal onto the first surface of the transmissive layer of the optical element and (ii) transmitting through or reflecting from the optical element at least a portion of the optical signal transformed substantially according to the effective phase transformation function φ eff (x,y).

3 . A method for making the optical element of claim 1 , the method comprising spatially selectively processing a layer comprising the first optical medium to replace, in selected volumes of the layer, the first optical medium with the second optical medium, thereby forming the transmissive layer of the optical element.

4 . The optical element of claim 1 wherein the transmissive layer includes areal regions for which either d 1 (x,y) or d 2 (x,y), but not both, are substantially equal to zero.

5 . The optical element of claim 4 wherein the transmissive layer includes (i) areal regions for which d 1 (x,y)≠0 and d 2 (x,y)=0, and (ii) areal regions for which d 1 (x,y)=0 and d 2 (x,y)≠0.

6 . The optical element of claim 4 wherein, at any given position (x,y), either d 1 (x,y) or d 2 (x,y), but not both, are substantially equal to zero.

7 . The optical element of claim 1 wherein the transmissive layer has a substantially uniform thickness d 1 (x,y)+d 2 (x,y)=D.

8 . The optical element of claim 1 wherein the second optical medium comprises a substantially solid material.

9 . The optical element of claim 1 wherein the second optical medium comprises vacuum, a gaseous material, or a liquid material.

10 . The optical element of claim 1 further comprising a solid substrate or overlayer positioned against the first surface of the transmissive layer, wherein the substrate or overlayer against the first surface is substantially transparent over the operational wavelength range.

11 . The optical element of claim 10 wherein the transmissive layer comprises a surface relief structure on a surface of the substrate against the first surface with the second optical medium substantially filling recessed regions of the surface relief structure.

12 . The optical element of claim 11 wherein the substrate against the first surface comprises material differing from the first and second optical media, and the surface relief structure is formed in a surface layer of the first optical medium on the substrate.

13 . The optical element of claim 11 wherein the substrate against the first surface comprises the same material as the first optical medium, and the surface relief structure is formed on a surface of the substrate.

14 . The optical medium of claim 10 wherein the substrate or overlayer against the first surface comprises the same material as the first or second optical medium.

15 . The optical medium of claim 10 wherein the substrate or overlayer against the first surface comprises material differing from the first and second optical media.

16 . The optical element of claim 1 wherein the discrete volumes of the multitude are distributed on the transmissive layer so that (2π/λ 0 )·(n 1 (λ 0 )·d 1 (x,y)+n 2 (λ 0 )·d 2 (x,y)), averaged over a sampling area having a largest transverse dimension about equal to λ 0 on the first surface of the transmissive layer, is substantially equal to the effective phase transformation function φ eff (x,y), and the optical element is structurally arranged to as to receive the optical signal incident on the first surface within the transmission region and to transmit through the second surface at least a portion of the incident optical signal transformed substantially according to the effective phase transformation function φ eff (x,y).

17 . The optical element of claim 16 wherein the transmissive layer has a substantially uniform thickness d 1 (x,y)+d 2 (x,y)=D that is substantially equal to Nλ 0 /|n 1 (λ 0 )−n 2 (λ 0 )|, where N is a non-zero integer.

18 . The optical element of claim 17 wherein N=1.

19 . The optical element of claim 16 further comprising a solid substrate or overlayer positioned against the second surface of the transmissive layer, wherein the substrate or overlayer against the second surface is substantially transparent over the operational wavelength range.

20 . The optical element of claim 19 wherein the transmissive layer comprises a surface relief structure on a surface of the substrate against the second surface with the second optical medium substantially filling recessed regions of the surface relief structure.

21 . The optical element of claim 20 wherein the substrate against the second surface comprises material differing from the first and second optical media, and the surface relief structure is formed in a surface layer of the first optical medi

Assignees

• Finisar Corp

Inventors

• Mossberg Thomas W
• Greiner Christoph M
• Iazikov Dmitri

Classifications

• G02B5/1866 Primary

  Transmission 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 title

• G02B5/1861

  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 title

• G02B5/1871 Primary

  Transmissive phase gratings · CPC title

• G02B26/06 Primary

  for controlling the phase of light (G02B26/08 takes precedence {, measuring optical phase difference G01J9/00}) · CPC title