Achromatic phase shift device and interferometer using achromatic phase shift device
First Claim
1. Achromatic phase shift device for introducing a wavelength independent optical phase shift in a first optical beam during operation, comprising at least one dispersive element,the at least one dispersive element comprising k element pairs (55k), k being an integer between 1 and M, each element pair being formed by respective first refractive means (2k) and second refractive means (4k), the respective first refractive means (2k) having a first refractive means input plane (6) for receiving a first optical beam (40) and a first refractive means output plane (8), the first refractive means input plane (6) and the first refractive means output plane (8) being at a predetermined angle β
-
k to each other, 0<
β
k<
π
/2, the respective second refractive means (4k) having a second refractive means input plane (10) and a second refractive means output plane (12), said second refractive means input plane (10) being positioned equidistant to the first refractive means output plane (8) and the second refractive means output plane (12) being positioned parallel to the first refractive means input plane (6), characterised in that the device (1) introduces a predetermined phase shift ψ
0 between the first optical beam (40) and a second optical beam (41), the second optical beam (41) running substantially parallel to the first optical beam (40) over an optical path length w0, a first optical axis (50) being defined from a device input surface (51) to a device output surface (52), the first refractive means (2k) having a first distance dk′
along the first optical axis (50) and the second refractive means having a second distance dk″
along the first optical axis (50), the first optical beam (40) being at an angle θ
k with the first optical axis (50) and a modified refractive index ak being defined as ak=nk cos θ
k, in which the sum dk of the first and second distance of the first and second refractive means (2k, 4k), respectively and the required optical path w0 are determined by solving the following equations for the wavelengths (λ
0 . . . λ
M) at which the predetermined phase shift ψ
0 should be obtained exactly;
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Abstract
The present invention relates to an achromatic phase shift device (1) for introducing a wavelength independent optical phase shift in a first optical beam (40) during operation, comprising at least one dispersive element (55k) formed by first refractive means (2k) and second refractive means (4k), the first refractive means (2k) having a first refractive means input plane (6) for receiving the first optical beam (40) and a first refractive means output plane (8) being at a predetermined angle (β) to each other, the second refractive means (4k) having a second refractive means input plane (10) and a second refractive means output plane (12) being positioned parallel to the first refractive means input plane (6). The device may comprise further pairs (55k) of respective first and second refractive means (2k, 4k). The present invention also relates to an interferometer comprising at least one achromatic phase shift device.
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Citations
14 Claims
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1. Achromatic phase shift device for introducing a wavelength independent optical phase shift in a first optical beam during operation, comprising at least one dispersive element,
the at least one dispersive element comprising k element pairs (55k), k being an integer between 1 and M, each element pair being formed by respective first refractive means (2k) and second refractive means (4k), the respective first refractive means (2k) having a first refractive means input plane (6) for receiving a first optical beam (40) and a first refractive means output plane (8), the first refractive means input plane (6) and the first refractive means output plane (8) being at a predetermined angle β -
k to each other, 0<
β
k<
π
/2,the respective second refractive means (4k) having a second refractive means input plane (10) and a second refractive means output plane (12), said second refractive means input plane (10) being positioned equidistant to the first refractive means output plane (8) and the second refractive means output plane (12) being positioned parallel to the first refractive means input plane (6), characterised in that the device (1) introduces a predetermined phase shift ψ
0 between the first optical beam (40) and a second optical beam (41), the second optical beam (41) running substantially parallel to the first optical beam (40) over an optical path length w0, a first optical axis (50) being defined from a device input surface (51) to a device output surface (52), the first refractive means (2k) having a first distance dk′
along the first optical axis (50) and the second refractive means having a second distance dk″
along the first optical axis (50), the first optical beam (40) being at an angle θ
k with the first optical axis (50) and a modified refractive index ak being defined as ak=nk cos θ
k,in which the sum dk of the first and second distance of the first and second refractive means (2k, 4k), respectively and the required optical path w0 are determined by solving the following equations for the wavelengths (λ
0 . . . λ
M) at which the predetermined phase shift ψ
0 should be obtained exactly;
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
comprising optical path delay means for introducing an optical path difference between the first optical path and the second optical path, characterized in that the interferometer further comprises at least one achromatic phase shift device according to claim 1, positioned in at least one of the first optical path and the second optical path. -
11. Interferometer according to claim 10, characterised in that an achromatic phase shift device is positioned in each optical path.
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12. Interferometer according to claim 10, characterised in that the interferometer comprises main control means for maintaining the phase shift (Ψ
- 0) between the at least first and second beam at a predetermined value, the main control means being connected to the optical path delay means (26, 27), and the first control means.
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13. Interferometer according to claim 12, characterised in that the predetermined value is equal to π
- .
-
k to each other, 0<
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14. Achromatic phase shift device for introducing a wavelength independent optical phase shift in a first optical beam during operation, comprising at least one dispersive element,
the at least one dispersive element comprising k element pairs (55k), k being an integer between 1 and M, each element pair being formed by respective first refractive means (2k) and second refractive means (4k), the first refractive means (2k) having a first refractive means input plane (6) for receiving a first optical beam (40) and a first refractive means output plane (8), the first refractive means input plane (6) and the first refractive means output plane (8) being at a predetermined angle β -
k to each other, 0<
β
k<
π
/2,the second refractive means (4k) having a second refractive means input plane (10) and a second refractive means output plane (12), said second refractive means input plane (10) being positioned equidistant to the first refractive means output plane (8) and the second refractive means output plane (12) being positioned parallel to the first refractive means input plane (6), characterised in that the device introduces a predetermined phase shift ψ
0 between the first optical beam (40) and a second optical beam (41), the second optical beam (41) running substantially parallel to the first optical beam (40) over an optical path length w0, a first optical axis (50) being defined from a device input surface (51) to a device output surface (52), the first refractive means (2k) having a first distance dk′
along the first optical axis (50) and the second refractive means having a second distance dk″
along the first optical axis (50), the first optical beam (40) being at an angle θ
k with the first optical axis (50) and a modified refractive index ak being defined as ak=nk cos θ
k,in which the sum dk of the first and second distance of the first and second refractive means (2k, 4k), respectively, and the required optical path w0 are determined by requiring constant terms and terms with λ
2, λ
3, . . . , λ
M to become zero and the term with λ
to become equal to ψ
0/2π
in the equation for the introduced optical path length difference wd(λ
) according toin which ak0, ak2, . . . =series expansion coefficients of the modified refractive index ak, according to
-
k to each other, 0<
Specification