Polarization rotator with frequency shifting phase conjugate mirror and simplified interferometric output coupler
First Claim
1. An interferometer for altering the polarization of a polarized input beam, comprising:
- an anisotropic prism that is uniaxial with respect to a c axis, said prism held by said support and including front, rear and multiple side surfaces, said prism being positionable to receive said input beam at its front surface, said rear prism surface lying in a plane that is angled to said front surface so as to receive said input beam at a first location after the beam has crossed the prism from said first surface, to refract a first one of the extraordinary (e) and ordinary (o) subbeams of said input beam out of the prism, and to reflect a second of said e and o subbeams towards said side surfaces by total internal reflection (TIR), said side surfaces being oriented to reflect said second subbeam by TIR back to said rear surface at a second location that is offset from said first location and at an angle such that said second subbeam is reflected by TIR off said rear surface on an exit path that exits the prism,a first adjustment mechanism for adjusting the relative angle between the input beam and prism so that the prism'"'"'s rear surface refracts one of the input beam'"'"'s o and e subbeams and reflects the other subbeam by TIR,a beam deflector,a deflector support supporting said beam deflector in the path of said first subbeam to redirect said first subbeam back to the prism'"'"'s rear surface at said second location, at an angle such that said first subbeam recombines with said second subbeam on said exit path, anda second adjustment mechanism for adjusting the relative angle between the first subbeam and the beam deflector to correct for errors in said angle,said deflector support being adjustable to hold said beam deflector at a position at which the first subbeam travels a path whose length differs from the path traveled by said second subbeam prior to their recombination, so as to alter the recombined beam'"'"'s polarization relative to the input beam polarization.
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Accused Products
Abstract
An interferometer that is used with a frequency shifting phase conjugate mirror (PCM), to produce a 90° polarization rotation, employs only two adjustable elements: a specially shaped prism, and a beam deflector that is preferably a porro prism. The primary prism is shaped and oriented so that a linearally polarized input beam is divided into ordinary (o) and extraordinary (e) subbeams. One of the subbeams is refracted out of the prism along a controlled length path, and then returned back into the prism by the deflector. The second subbeam is retained within the prism by total internal reflection, and directed onto a exit path that coincides with the path of the first subbeam after its reentry into the prism. The recombined output beam is directed into the PCM, from which it is reflected back into the prism for a reverse pass. The difference in path lengths between the o and e subbeams is selected to produce a net 90° polarization rotation after both passes.
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Citations
22 Claims
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1. An interferometer for altering the polarization of a polarized input beam, comprising:
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an anisotropic prism that is uniaxial with respect to a c axis, said prism held by said support and including front, rear and multiple side surfaces, said prism being positionable to receive said input beam at its front surface, said rear prism surface lying in a plane that is angled to said front surface so as to receive said input beam at a first location after the beam has crossed the prism from said first surface, to refract a first one of the extraordinary (e) and ordinary (o) subbeams of said input beam out of the prism, and to reflect a second of said e and o subbeams towards said side surfaces by total internal reflection (TIR), said side surfaces being oriented to reflect said second subbeam by TIR back to said rear surface at a second location that is offset from said first location and at an angle such that said second subbeam is reflected by TIR off said rear surface on an exit path that exits the prism, a first adjustment mechanism for adjusting the relative angle between the input beam and prism so that the prism'"'"'s rear surface refracts one of the input beam'"'"'s o and e subbeams and reflects the other subbeam by TIR, a beam deflector, a deflector support supporting said beam deflector in the path of said first subbeam to redirect said first subbeam back to the prism'"'"'s rear surface at said second location, at an angle such that said first subbeam recombines with said second subbeam on said exit path, and a second adjustment mechanism for adjusting the relative angle between the first subbeam and the beam deflector to correct for errors in said angle, said deflector support being adjustable to hold said beam deflector at a position at which the first subbeam travels a path whose length differs from the path traveled by said second subbeam prior to their recombination, so as to alter the recombined beam'"'"'s polarization relative to the input beam polarization. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An apparatus for rotating the polarization of a forward directed linearly polarized input beam, comprising:
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a shaped anisotropic prism positioned in the input beam path and having a surface oriented to separate the input beam into ordinary (o) and extraordinary (e) subbeams, said prism being shaped to direct a first one said subbeams out of the prism along a first exit path, and to direct the second of said subbeams out of the prism along a second exit path that includes total internal reflection (TIR) prior to exiting the prism, said prism including a front surface for receiving said input beam, and a rear surface that is uncoated and is oriented at an angle to said input beam after it has crossed the prism from the front surface, the angle of said rear surface being selected to effect said separation into said e and o subbeams, a beam deflector positioned in the path of said first subbeam after it exits said prism to redirect said first subbeam back into the prism for recombination with said second subbeam along said second exit path, said beam deflector being spaced from said prism such that the relative phase of the o and e beam polarizations after recombination is different from their relative phase immediately after being separated from the input beam, and means for shifting the frequency of said recombined beam, and for redirecting said recombined beam in the reverse direction back through said prism so that said frequency shifted beam is separated into o and e subbeams that travel in the reverse direction along the paths of the input beam'"'"'s o and e subbeams and acquire a phase differential before being recombined into an output beam, the distance between said beam deflector and said prism being selected so that, for the frequency shift imparted by said frequency shifting means, the net phase differential between the o and e subbeams in the forward and reverse directions imparts a linear polarization to the return beam that is rotated relative to the input beam polarization. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification