Dielectric layer polarizer
First Claim
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1. A dielectric layer polarizer comprising;
- a substrate having a face which is oblique to an incident light beam to be polarized, said polarizer further comprising a stack of alternating low and high refractive index dielectric layers on said oblique face, wherein said stack is symmetrical and begins and ends with respective half-thickness layers, said half thickness layers having a same refractive index and each having the thickness of the other layers of the stack which have the same refractive index.
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Abstract
The invention relates in particular to polarizing light whose angle of incidence may vary substantially, e.g. over ±10°. A polarizing stack (22) constituted by dielectric layers (30, 31, 32, 33, 34, . . . ) is formed on an oblique face (4). It is in the form of a repetitive sucession of symmetrical sequences (30, 31, 40) each constituted by two half-thickness low refractive index layers (30, 40) on either side of a high refracture index layer (31). The invention is particularly applicable to polarizing the light emitted by a semiconductor laser.
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Citations
6 Claims
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1. A dielectric layer polarizer comprising;
- a substrate having a face which is oblique to an incident light beam to be polarized, said polarizer further comprising a stack of alternating low and high refractive index dielectric layers on said oblique face, wherein said stack is symmetrical and begins and ends with respective half-thickness layers, said half thickness layers having a same refractive index and each having the thickness of the other layers of the stack which have the same refractive index.
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2. A dielectric layer polarizer for polarizing light having a wavelength, said polarizer comprising:
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inlet means for forming or transmitting an incident beam which is constituted by said light and whose rays propagate along directions close to a predetermined direction of incidence; a transparent substrate having a face on the path of said incident beam, said face being oblique relative to said direction of incidence; and a polarizing stack formed on said oblique face and constituted by thin dielectric layers, said layers being first and second refractive index polarizing layers presenting a first refractive index and a second refractive index for said light and following one another in alternation starting from said oblique face and having different thicknesses, with the succession of said layers being in the form of a periodic succession of base sequences, each of which is constituted by a plurality of thin dielectric layers alternating between said first and second refractive indices, said sequences being identical to each other with respect to their refractive indices and the thicknesses of the layers which constitute them; said direction of incidence forming an angle of incidence with the direction perpendicular to said oblique face and to said polarizing layers, said angle of incidence being situated in a plane of incidence and having a value relative to said wavelength and to said refractive indices and thicknesses of the polarizing layers such that said polarizing stack separates said incident beam into a transmitted beam and a reflected beam with crossed polarizations; wherein said base sequence is a symmetrical sequence constituted by one of said second index polarizing layers having a second index optical thickness, and two mutually identical half-thickness first index layers situated on either side of said second index layer and each of them having a first index optical thickness which is half said second optical thickness, such that pairs of said half-thickness first index layers combine at each interface between two consecutive base sequences in order to form one of said first index polarizing layers which is of full thickness. - View Dependent Claims (3, 4, 5, 6)
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Specification