90-degree independent polarization optical hybrid

Abstract

The invention relates to a 90-degree optical hybrid (1), comprising two inlets (21,22) spaced a distance D apart and adapted to receive a first light beam (S) and a second light beam (L).According to the invention, the optical hybrid comprises a first beam splitter (12) and a second combiner-splitter (13) arranged at 90 degrees to the first beam splitter. The first beam splitter (12) is adapted to angularly split an incident beam into two perpendicular subbeams, and the second combiner-splitter has a first face (131) exhibiting alternating regions with distinct optical coatings and a second reflective face. These regions are arranged to collect the light beams separated by the first beam splitter, separate them, and recombine them to form four interference light signals (S+L, SL, S+iL, S-iL) phase-shifted by 90-degree steps and each directed to one of the four outputs (31, 32, 33, 34) of the optical hybrid. Figure for the abstract: Fig. 1.

Claims

1. Demands A 90-degree optical hybrid (1), comprising a first inlet (21) adapted to receive a first light beam (S) and a second inlet (22) adapted to receive a second light beam (L), the first inlet (21) and the second inlet (22) being separated by a distance D, a first optical axis of the first light beam (S) and a second optical axis of the second light beam (L) being parallel, characterized in that the 90-degree optical hybrid (1) comprises: a first beam splitter (12) with flat, parallel faces, arranged at 45 degrees to the first optical axis and the second optical axis, a first face (121) of the first beam splitter being oriented towards the first entrance (21) and the second entrance (22), a second face (122) of the first beam splitter (12) being opposite the first face (121), the first beam splitter (12) being configured to angularly separate the first light beam (S) and the second light beam (L) into four light beams (ST, SR, LT, LR), comprising a first reflected light beam (SR), a first transmitted light beam (ST), a second reflected light beam (LR), a second transmitted light beam (LT), and a second combiner-splitter (13) with flat, parallel faces of a thickness E, and arranged at 90 degrees to the first beam splitter (12) and at -45 degrees to the first optical axis and to the second optical axis,a first face (131) of the second combiner-divider plate (13) being oriented towards the first beam splitter plate (12), a second face opposite the first face (131) of the second combiner-divider plate (13) comprising a reflective coating, at least one phase-shifting plate (141, 142) is placed on an optical path of at least one of the four light beams (ST, SR, LT, LR) between the first beam splitter plate (12) and the second combiner-divider plate (13), the first face (121) of the second combiner-divider plate is divided into a plurality of regions (1311, 1312, 1313, 1314, 1315, 1316) comprising, respectively, a first region (1311), a second region (1312), a third region (1313), arranged in series approaching the side of the second face (122) of the first separating blade (12), a fourth region, (1314), a fifth region (1315) and a sixth region (1316) arranged in series moving away from the side of the first face (121) of the first separating blade (12), where: - the second region (1312) and the fifth region (1315) include a semi-reflective treatment, - the first, third, fourth and sixth regions (1311, 1313, 1314, 316) include an anti-reflective coating, - the second region (1312) being arranged to intercept an optical axis of the first transmitted light beam (ST) and the third region (1313) being arranged to intercept an optical axis of the second transmitted light beam (LT), - the first region (1311) being arranged to receive a portion of the first transmitted light beam (ST) transmitted through the second region (1312) and reflected on the second face (132) of the second combiner-divider blade (13) and a portion of the second transmitted light beam (LT) transmitted through the third region (1313), reflected on the second region (1312) and on the second face (132) of the second combiner-divider blade (13), to form a first interference light signal (S+L) directed towards a first output (31), - the second region (1312) being arranged to receive and combine a portion of the first transmitted light beam (ST) and a portion of the second transmitted light beam (LT) transmitted through the third region (1313) and reflected on the second face (132) of the second combiner-divider blade to form a third interference light signal (SL) directed towards a third output (33), - the fourth region (1314) being arranged to intercept the optical axis of the second reflected light beam (LR) and the fifth region (1315) being arranged to intercept the optical axis of the first reflected light beam (SR), - the fifth region (1315) being arranged to receive and combine a portion of the first reflected light beam (SR), and a portion of the second reflected light beam (LR) transmitted through the fourth region (1314) and reflected on the second face (132) of the second combiner-divider blade (13) to form a second interference light signal (S+iL) directed towards a second output (32); - the sixth region (1316) being arranged to receive a portion of the first reflected light beam (SR) transmitted through the fifth region (1315) and reflected on the second face (132) of the second combiner-divider blade (13) and a portion of the second reflected light beam (LR) transmitted through the fourth region (1314), reflected on the fifth region (1315) and on the second face (132) of the second combiner-divider blade (13), to form a fourth interference light signal (S-iL) directed towards a fourth output (34); - said at least one phase-shifting blade (141, 142) being arranged and adapted to induce a phase shift between the first interference light signal (S+L) and the second interference light signal (S+iL), and between the third interference light signal (SL) and the fourth interference light signal (S-iL).

2. 90-degree optical hybrid according to claim 1, wherein the first light beam (S) and the second light beam (L) have a wavelength equal to a nominal operating wavelength 2q, the phase shift induced by at least one phase-shifting plate, between the first interfering light signal (S+L) and the second interfering light signal (S+iL), and between the third interfering light signal (SL) and the fourth interfering light signal (S-iL) is equivalent to a path difference, in absolute value, of k*(W2)+(X0 / 4), where k is an integer.

3. 90-degree optical hybrid according to claim 2, wherein k is equal to zero.

4. 90-degree optical hybrid according to any one of claims 1 to 3, wherein at least one phase-shifting blade comprises a first phase-shifting blade (141) and a second phase-shifting blade (142), the first phase-shifting blade (141) being disposed on an optical path of the first transmitted light beam (ST), the second phase-shifting blade (142) being disposed on an optical path of the first reflected light beam (SR).

5. 90-degree optical hybrid according to claim 4, wherein the first phase-shifting blade (141) has a thickness equal to El, and the second phase-shifting blade (142) of refractive index n, has an optical thickness equal to E1+ n* (Xo / (4*(nl)).

6. 90-degree optical hybrid according to any one of claims 1 to 5, wherein the first face (121) of the first beam splitter (12) comprises a semi-reflective coating adapted to angularly separate the first light beam (S) and the second light beam (L) or wherein the second face (121) of the first beam splitter (12) comprises a semi-reflective coating adapted to angularly separate the first light beam (S) and the second light beam (L)

7. 90-degree optical hybrid according to any one of claims 1 to 6, wherein the thickness E of the second combiner-divider plate (13) of refractive index n, is equal to D / (^2 * tan(arcsin(sin(45°) / n))).

8. 90-degree optical hybrid according to any one of claims 1 to 7, wherein the 90-degree optical hybrid (1) comprises at least one rotation means (144) of at least one phase-shifting blade (141, 142), an axis of rotation of at least one rotation means being perpendicular to a plane comprising the first optical axis and the second optical axis.

9. 90-degree optical hybrid according to any one of claims 1 to 8, wherein the 90-degree optical hybrid (1) comprises at least one heating means (146) for at least one phase-shifting blade (141, 142).

10. A 90-degree optical hybrid according to any one of claims 1 to 9, wherein the distance between the first region (1311) and the second region (1312), between the second region (1312) and the third region (1313), between the fourth region (1314) and the fifth region (1315), and between the fifth region (1315) and the sixth region (1316) is equal to -^2D-

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