Method for producing a diffraction grating

Patent metadata

Field	Value
Publication number	US-9323070-B2
Application number	US-201214124002-A
Country	US
Kind code	B2
Filing date	Jun 7, 2012
Priority date	Jun 8, 2011
Publication date	Apr 26, 2016
Grant date	Apr 26, 2016

Abstract

A manufacturing method for a grating is disclosed for the angular dispersion of light impinging the grating. The grating comprises tapered structures and cavities. A cavity width and/or corrugation amplitude is varied for achieving a desired grating efficiency according to calculation. A method is disclosed for conveniently creating gratings with variable cavity width and/or corrugation amplitude. The method comprises the step of anisotropically etching a groove pattern into a grating master. Optionally a replica is produced that is complementary to the grating master. By variation of an etching resist pattern, the cavity width of the grating may be varied allowing the optimization towards different efficiency goals.

First claim

The invention claimed is:

1. Method of manufacturing a master grating for diffracting light of a particular wavelength impinging the master grating with a particular angle of incidence, the master grating comprising an array of grooves running in parallel along a planar face of the master grating, the grooves distanced by a grating period; the grooves comprising a triangular profile with flat interfaces, wherein one of the interfaces forms a blaze angle with respect to the planar face; wherein the method comprises
providing a wafer comprising a substantially mono-crystalline material, the material having first, second, and third crystal planes, wherein the first and second crystal planes intersect each other at an intersection angle; the wafer being cut along a wafer surface having a cut angle equal to the blaze angle with respect to the first crystal plane;
applying an etching resistant material to parts of the wafer surface in a pattern of parallel strips, the centers of the strips distanced by the grating period, wherein exposed parts of the wafer surface are formed between the strips;
applying an anisotropic etching process to the wafer surface that etches faster in a direction normal to the third crystal plane than in a direction normal to the first and second crystals planes to form the grooves at the exposed parts wherein the flat interfaces of the grooves are formed along the first and second crystal planes; wherein the method further comprises
calculating a corrugation amplitude of the grooves with respect to the wafer surface as a function of a desired diffraction efficiency of the light for the given grating period and blaze angle; and
in the applying of the etching resistant material, controlling a line width of the strips such that the grooves are formed with the flat interfaces extending from exposed edges of neighboring strips into the wafer surface and intersecting each other with the intersection angle at a depth equal to the calculated corrugation amplitude.

2. Method of manufacturing a replica grating, the method comprising
manufacturing a master grating according to claim 1 ;
applying a moldable material to the master grating to form the replica grating wherein the replica grating comprises an array of ridges complementary to the array of grooves of the master grating; and
separating the replica grating from the master grating; wherein
said calculating of the corrugation amplitude is performed as a function of the desired diffraction efficiency of the replica grating.

3. Method according to claim 1 wherein the mono-crystalline material is silicon.

4. Method according to claim 1 , further comprising applying a reflective layer to the master grating or to a replica grating of the master grating.

5. Method according to claim 1 , wherein the strips of the etching resistant material are provided on the wafer using imprint lithography.

6. Method according to claim 1 wherein, prior to applying the anisotropic etching process, the width of the strips is narrowed using reactive ion etching.

7. Method according to claim 1 , wherein the corrugation amplitude is set in accordance with a desired diffraction efficiency being a maximum achievable diffraction efficiency as a function of the corrugation amplitude.

8. Method according to claim 1 , wherein the corrugation amplitude is set in accordance with a desired diffraction efficiency, wherein TE and TM polarization states of the impinging light have a maximum achievable difference in diffraction efficiency as a function of the corrugation amplitude.

9. Method according to claim 1 wherein the corrugation amplitude is set in accordance with a desired diffraction efficiency, wherein diffraction efficiency for TE and TM polarization states of the impinging light is equal.

Assignees

• Vink Henri Johannes Petrus
• Visser Huibert
• Van Amerongen Aaldert Hidde
• TNO

Inventors

• Vink Henri Johannes Petrus
• Visser Huibert
• Van Amerongen Aaldert Hidde

Classifications

• H01S3/092

  of flash lamp (H01S3/0937 takes precedence {; flash lamps per se H01J61/80; circuit arrangements for operating flash lamps in general H05B41/30}) · CPC title

• G01J3/18

  using diffraction elements, e.g. grating (gratings per se G02B) · CPC title

• G02B5/1866

  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

• G02B5/1828

  having means for producing variable diffraction (controlling the direction of light by means of one or more diffracting elements G02B26/0808; acousto-optical elements G02F1/11, G02F1/33; electro- or magneto-optical diffraction G02F1/292, G02F1/2955) · CPC title

• H01S3/1636

  Al2O3 (Sapphire) · CPC title