Tunable optical Active Elements

• US 20090310209A1
• Filed: 02/06/2007
• Published: 12/17/2009
• Est. Priority Date: 02/07/2006
• Status: Active Grant

• Current Assignee: ETH Transfer (ETH Zurich), ETH Zurich
• Original Assignee: ETH Transfer (ETH Zurich), ETH Zurich
• Inventors: Beck, Markus Daniel, Aschwanden, Manuel, Belyaev, Yury, Stemmer, Andreas
• Granted Patent: US 7,920,330 B2
• Time in Patent Office: Days
• US Class Current: 359/291
• CPC Class Codes: G02B 26/0808 by means of one or more diffracting elements
• CPC Class Codes: G02B 5/1828 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 Class Codes: G02B 5/1847 Manufacturing methods

Abstract

The invention is directed to different optical active elements (1, 20, 22) such as tunable diffraction gratings and tunable phase shifters having in general a similar setup. The optical active elements (1, 20, 22) comprise an intermediate layer (4) made out of a deformable material which is mechanically interconnected to a driving means. The driving means comprises a first and a second driving plate (2, 3) arranged in general opposite to each other on opposite sides of and at least partially covering the intermediate layer (4) such that a local compression of the intermediate layer (4) by the driving plates (2, 3) causes a local reduction of the thickness in a first direction. This reduction in a first direction causes a secondary deformation of the intermediate layer in a second direction which results in a change of the optical behavior of the optical active element.

Claims

1. An optical active element (1, 20, 21) comprising:

an intermediate layer (4) made out of a deformable material and mechanically interconnected to a first and a second driving plate (2, 3) arranged in general opposite to each other on opposite sides of and partially covering the intermediate layer (4) such that a local compression of the intermediate layer (4) by the driving plates (2, 3) causes a local reduction of the thickness (B) of the intermediate layer (4) in a first direction (x) and at least one thereto by the poisson'"'"'s ratio of the material of the intermediate layer (4) related secondary deformation of the intermediate layer (4) in a second direction (y, z, dr) whereby the secondary deformation causes a change in the optical behavior of the optical active area (5).

2. The optical active element (1, 20, 21) according to claim 1 wherein the first and the second driving plates (2, 3) are a first and a second electrode (2, 3) arranged such that when a voltage (V) is applied between the first and the second electrode (2, 3), the first and the second electrode (2, 3) attract each other due to coulomb forces (Fc).

3. The optical active element (1, 20, 21) according to claim 2, wherein at least one of the electrodes (2, 3) consists of carbon black.

4. The optical active element (1, 20, 21) according to claim 1 wherein the intermediate layer (4) is attached to a holding means (6) in a prestretched manner such that the intermediate layer (4) does not deform out of plane (y, z) during operation.

5. The optical active element (1, 20, 21) according to claim 4 wherein the holding means (6) has one of a circular and a square opening in which the intermediate layer (4) is arranged.

6. The optical active element (1, 20, 21) according to claim 2 wherein the electrodes (2, 3) are arranged laterally to the optical active area (5).

7. The optical active element (1, 20, 21) according to claim 1 wherein the intermediate layer (4) has a thickness (B) in the range of 100 nm to 150 μ

m.

8. The optical active element (1, 20, 21) according to claim 1 wherein the intermediate layer (4) has a diameter in the range of 10 μ

m to 500 mm.

9. The optical active element (1, 20, 21) according to claim 1 wherein an area of the intermediate layer (4) not covered by the driving plates (2, 3) has an adjustable diameter which is related to the compression of the intermediate layer (4) in the first direction (x) by the poisson'"'"'s ratio of the material.

10. The optical active element (1, 20, 21) according to claim 9 wherein the area with the adjustable diameter comprises a diffraction grating (5) with an adjustable grating period (d).

11. The optical active element (1, 20, 21) according to claim 10 wherein the diffraction grating (5) is a Fresnel-Lens.

12. The optical active element (1, 20, 21) according to claim 10 wherein the diffraction grating (5) comprises one of an injection molded, or spin-coated and stamped material.

13. The optical active element (1, 20, 21) according to claim 1 wherein an optical active area (5) of the intermediate layer (4) not covered by the driving plates is transparent and has an adjustable thickness (B) which is related to the compression of the intermediate layer (4) in the first direction (x) by the poisson'"'"'s ratio of the material.

14. The optical active element (1, 20, 21) according to claim 13 wherein the optical active area (5) acts as phase shifting element.

15. The optical active element (1, 20, 21) according to claim 13 wherein the optical active area (5) acts as a lens having a variable focus.

16. The optical active element (1, 20, 21) according to claim 15 wherein the lens comprises a lens-shaped chamber (16) delimited by two foil-like areas (14).

17. The optical active element (1, 20, 21) according to claim 16 wherein the lens-shaped chamber (16) is filled with a material having a higher refractive index then the surrounding environment.

18. The optical active element (1,20, 21) according to claim 16 wherein the lens-shaped chamber (16) is filled with a liquid.

19. The optical active element (1,20, 21) according to claim 9 wherein the diffraction grating (5) is implemented in the surface of the intermediate layer (4) or attached to the surface of the intermediate layer (4) as a separate element.

20. A microscope comprising at least one optical element (1, 20, 21) according to claim 1.

21. The microscope (50) according to claim 20 wherein the microscope (50) comprises a laser beam (47) by which a laser (51) is directed onto a diffraction grating (1) by which the laser beam (47) is decomposed in several deviated diffraction maxima (48, 49) to provide a structured illumination of a specimen.

22. The microscope (50) according to claim 21 wherein four of the several decomposed laser beams (48, 49) are arranged rotationally symmetric around an optical axis (46).

23. The microscope (50) according to claim 20 wherein the microscope is a telecentric (50) beam system.

24. The microscope (50) according to claim 20 wherein the optical illumination path of the microscope (50) comprises a first lens (65) to shape the laser beam (47), a diffraction grating (1) to decompose the shaped laser beam after the first lens (65), a second lens (63) to converge the decomposed laser beams (48, 49) after the diffraction grating (1) and a third lens (59) to arrange the decomposed laser beams (48, 49) parallel to the optical axis (46).

25. The microscope (50) according to claim 24 wherein the optical illumination path of the microscope (50) comprises a lambda half wave plate (52) and a phase shifter (53).

26. A method for making of an optical element (1, 20, 21) according to claim 1 comprising the following steps:

a) stretching the intermediate layer (4) by 200% to 300% resulting in a prestretched intermediate layer (4);

b) attaching the prestretched intermediate layer (4) to a holding means (6); and

c) applying on each side of the intermediate layer (4) an electrode (2, 3) at least partially covering the intermediate layer (4).

27. The method for making of the optical element (1, 20, 21) according to claim 26 further comprising:

applying a grating (5) to the intermediate layer (4).

28. The method for making the optical element (1, 20, 21) according to claim 27 wherein the grating (5) is made by one of spin coating, injection molding, and thermal forming.

29. The method according to claim 26 wherein the electrode (2, 3) consists of carbon black powder which is stamped and/or sprayed and/or coating and/or contact printed.