Patent US4744272A successfully refreshed from Google Patents.
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EP0390604A2
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EP
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Quasi-achromatic optical isolators and circulators
Assignee: Verizon Laboratories Inc
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Filing: 1990-03-30
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Granted: —
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Expires: 2010-03-30
Abstract
Abstract A quasi-achromatic configuration of two Faraday elements (85, 87) and five birefringent plates (86, 88) which when suitably oriented between two linearly polarizing elements (84, 89) would constitute an optical isolator or circulator. The nominal Faraday rotations of the two elements are 45° and 90° at a center design wavelength about which the devices are to operate. Changes in these rotations due to either wavelength or temperature variations compensate one another because of their coupling by the birefringent plates. In this way a higher degree of isolation is obtained over a wider optical bandwidth than would be possible in a device using a single 45° Faraday element. A group of three plates (86) is used between the two Faraday elements (85, 87) and two more (88) follow them to give the required polarization transformations which must themselves be quasi-achromatic over the desired wavelength range.
Inventors
- 👤 Carl F. Buhrer
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 16:22
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/01; G02F1/09; G02F1/093; G02F2201/00; G02F2201/16; G02F2203/00; G02F2203/04
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
132 words
A quasi-achromatic optical isolator through which a light beam within a wavelength range about a nominal wavelength may propagate and comprising in sequence: a first plane polarizer accepting said light beam as input; a first Faraday rotator receiving the light beam which has passed through said first plane polarizer; a first linearly birefringent plate receiving the light beam which has passed through said first Faraday rotator; a second Faraday rotator receiving the light beam which has passed through said first linearly birefringent plate; a second linearly birefringent plate receiving the light beam which has passed through said second Faraday rotator; and a second plane polarizer receiving the light beam which has passed through said second linearly birefringent plate, transmitting said light beam undiminished in intensity, and exiting said light beam as output.
Claim 2
Dependent Claim
132 words
A quasi-achromatic optical isolator through which a light beam within a wavelength range about a nominal wavelength may propagate and comprising in sequence: a first plane polarizer accepting said light beam as input; a first Faraday rotator receiving the light beam which has passed through said first plane polarizer; a first linearly birefringent plate receiving the light beam which has passed through said first Faraday rotator; a second Faraday rotator receiving the light beam which has passed through said first linearly birefringent plate; a second linearly birefringent plate receiving the light beam which has passed through said second Faraday rotator; and a second plane polarizer receiving the light beam which has passed through said second linearly birefringent plate, transmitting said light beam undiminished in intensity, and exiting said light beam as output.
Claim 3
Dependent Claim
34 words
The optical isolator of claim 1 wherein a light beam propagating along the +z axis through said optical isolator is plane polarized at zero degrees to the x axis by said first plane polarizer.
Claim 4
Dependent Claim
30 words
The optical isolator of claim 2 wherein: said first Faraday rotator has a rotation angle of +n degrees; and said second Faraday rotator has a rotation angle of +2n degrees.
Claim 5
Dependent Claim
32 words
The optical isolator of claim 3 wherein said first and said second linearly birefringent plates have +120 degrees of retardation with their fast axes oriented at zero degrees to the x axis.
Claim 6
Dependent Claim
32 words
The optical isolator of claim 3 wherein said first and said second linearly birefringent plates have -120 degrees of retardation with their fast axes oriented at zero degrees to the x axis.
Claim 7
Dependent Claim
30 words
The optical isolator of claim 2 wherein: said first Faraday rotator has a rotation angle of +n degrees; and said second Faraday rotator has a rotation angle of -2n degrees.
Claim 8
Dependent Claim
32 words
The optical isolator of claim 6 wherein said first and said second linearly birefringent plates have +60 degrees of retardation with their fast axes oriented at zero degrees to the x axis.
Claim 9
Dependent Claim
32 words
The optical isolator of claim 6 wherein said first and said second linearly birefringent plates have -60 degrees of retardation with their fast axes oriented at zero degrees to the x axis.
Claim 10
Dependent Claim
34 words
The optical isolator of claim 3 or 6 wherein: n = +45 degrees at said nominal wavelength; and the orientation of the polarization axis of said second plane polarizer is equal to -45 degrees.
Claim 11
Dependent Claim
34 words
The optical isolator of claim 3 or 6 wherein: n = -45 degrees at said nominal wavelength; and the orientation of the polarization axis of said second plane polarizer is equal to +45 degrees.
Claim 12
Dependent Claim
34 words
The optical isolator of claim 1 wherein said Faraday rotators are composed of the same material such that they have exactly proportional wavelength and temperature dependencies, thereby compensating for wavelength changes and temperature variations.
Claim 13
Dependent Claim
16 words
The optical isolator of claim 11 wherein the Faraday rotators comprise crystals of yttrium iron garnet.
Claim 14
Dependent Claim
20 words
The optical isolator of claim 1 wherein said birefringent plates are constructed for said nominal wavelength equal to 1.4 µm.
Claim 15
Dependent Claim
167 words
A quasi-achromatic optical circulator having first, second, third, and fourth ports that may accept a light beam within a wavelength range about a nominal wavelength and direct it to a succeeding port and comprising: a first polarizing beam splitter adjacent said first and said third ports of said circulator; a first Faraday rotator receiving a light beam which has passed through said first polarizing beam splitter; a first plurality of linearly birefringent plates receiving the light beam which has passed through said first Faraday rotator; a second Faraday rotator receiving the light beam which has passed through said first plurality of linearly birefringent plates; a second plurality of linearly birefringent plates receiving the light beam which has passed through said second Faraday rotator; and a second polarizing beam splitter adjacent said second and said fourth ports of said circulator for receiving the light beam which has passed through said second plurality of linearly birefringent plates and directing said light beam undiminished in intensity to said succeeding port.
Claim 16
Dependent Claim
167 words
A quasi-achromatic optical circulator having first, second, third, and fourth ports that may accept a light beam within a wavelength range about a nominal wavelength and direct it to a succeeding port and comprising: a first polarizing beam splitter adjacent said first and said third ports of said circulator; a first Faraday rotator receiving a light beam which has passed through said first polarizing beam splitter; a first plurality of linearly birefringent plates receiving the light beam which has passed through said first Faraday rotator; a second Faraday rotator receiving the light beam which has passed through said first plurality of linearly birefringent plates; a second plurality of linearly birefringent plates receiving the light beam which has passed through said second Faraday rotator; and a second polarizing beam splitter adjacent said second and said fourth ports of said circulator for receiving the light beam which has passed through said second plurality of linearly birefringent plates and directing said light beam undiminished in intensity to said succeeding port.
Claim 17
Dependent Claim
26 words
The optical circulator of claim 14 wherein the orientations of the polarization axes of said first polarizing beam splitter are equal to 0 and 90 degrees.
Claim 18
Dependent Claim
30 words
The optical circulator of claim 15 wherein: said first Faraday rotator has a rotation angle of +n degrees; and said second Faraday rotator has a rotation angle of +2n degrees.
Claim 19
Dependent Claim
39 words
The optical circulator of claim 16 wherein said first plurality of linearly birefringent plates constitutes a combination plate quasi-achromatic about said nominal wavelength and equivalent to an optical rotator followed by a linear retardation between +116 and +120 degrees.
Claim 20
Dependent Claim
39 words
The optical circulator of claim 16 wherein said first plurality of linearly birefringent plates constitutes a combination plate quasi-achromatic about said nominal wavelength and equivalent to an optical rotator followed by a linear retardation between -116 and -120 degrees.
Claim 21
Dependent Claim
30 words
The optical circulator of claim 15 wherein: said first Faraday rotator has a rotation angle of +n degrees; and said second Faraday rotator has a rotation angle of -2n degrees.
Claim 22
Dependent Claim
39 words
The optical circulator of claim 19 wherein said first plurality of linearly birefringent plates constitutes a combination plate quasi-achromatic about said nominal wavelength and equivalent to an optical rotator followed by a linear retardation between +60 and +64 degrees.
Claim 23
Dependent Claim
39 words
The optical circulator of claim 19 wherein said first plurality of linearly birefringent plates constitutes a combination plate quasi-achromatic about said nominal wavelength and equivalent to an optical rotator followed by a linear retardation between -60 and -64 degrees.
Claim 24
Dependent Claim
17 words
The optical circulator of claim 16 or 19 wherein n = +45 degrees at said nominal wavelength.
Claim 25
Dependent Claim
17 words
The optical circulator of claim 16 or 19 wherein n = -45 degrees at said nominal wavelength.
Claim 26
Dependent Claim
26 words
The optical circulator of claim 15 wherein the orientations of the polarization axes of said second polarizing beam splitter are equal to 0 and 90 degrees.
Claim 27
Dependent Claim
34 words
The optical circulator of claim 14 wherein the transmission in the forward direction between succeeding ports and the isolations between non succeeding ports are optimized at two wavelengths symmetrically displaced from said nominal wavelength.
Claim 28
Dependent Claim
43 words
The optical circulator of claim 14 wherein said second plurality of linearly birefringent plates constitutes a combination plate quasi-achromatic about said nominal wavelength for converting elliptically polarized light from said second Faraday rotator to plane polarized, light for transmission by said second polarizer.
References Cited (Backward Citations)
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