# US 10,120,213 B2 · Temperature-compensated optical isolator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,120,213 B2 - Document ID: US10120213B2 - Status: Granted - Kind: B2 - Application number: 14/993,660 - Filed: 2016-01-12 - Published: 2017-07-13 - Granted: 2018-11-06 - Earliest claimed: 2016-01-12 - Assignees: TOPTICA Phtonics Inc. USA - Applicants: TOPTICA Photonics Inc. USA - Inventors: Frank Diedrich; Jerry Kuper - Web page: https://patentgrep.com/patent/US10120213B2 ## CPC - G02F 1/093: {used as non-reciprocal devices, e.g. optical isolators, circulators (G02F1/0955 takes precedence)} - G02F 2203/60: Temperature independent - G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS ## Abstract The invention relates to an optical isolator comprising a polarizer adapted to polarize a beam of incident light to form a beam of polarized light, an analyzer adapted to transmit said beam of polarized light and to polarize back-reflected light, a magneto-optical element disposed between the polarizer and the analyzer, which magneto-optical element rotates the polarization direction of said beam of polarized light, and a magnet generating a magnetic field penetrating said magneto-optical element. It is an object of the invention to provide a temperature-compensated optical isolator that achieves a high degree of isolation at a minimum insertion loss over a given temperature range, without any need of manual tuning. The invention proposes to make provision for an automatic actuator mechanically connected to said magneto-optical element to move said magneto-optical element relative to said magnet in response to a temperature variation or in response to a variation of the wavelength of the incident light. Alternatively, the automatic actuator may be mechanically connected to said magnet to move said magnet relative to said magneto-optical element. ## Claims ### Claim 1 An optical isolator comprising: a polarizer adapted to polarize a beam of incident light to form a beam of polarized light; an analyzer adapted to transmit said beam of polarized light and to polarize back-reflected light; a magneto-optical element disposed between the polarizer and the analyzer, which magneto-optical element rotates the polarization direction of said beam of polarized light; a magnet generating a magnetic field penetrating said magneto-optical element; and an automatic actuator mechanically connected to said magneto-optical element to move said magneto-optical element relative to said magnet in response to one or more of a temperature variation and a variation of the wavelength of said incident light, wherein said automatic actuator further comprises a thermal expansion element comprising a piston that is axially movable in a cylinder filled with a fluid having a non-zero thermal expansion coefficient. ### Claim 2 (depends on 1) The isolator of claim 1, wherein said fluid further comprises one or more of hydraulic oil, acetone, and ammonia. ### Claim 3 An optical isolator comprising: a polarizer adapted to polarize a beam of incident light to form a beam of polarized light; an analyzer adapted to transmit said beam of polarized light and to polarize back-reflected light; a magneto-optical element disposed between the polarizer and the analyzer, which magneto-optical element rotates the polarization direction of said beam of polarized light; a magnet generating a magnetic field penetrating said magneto-optical element; and an automatic actuator mechanically connected to said magneto-optical element to move said magneto-optical element relative to said magnet in response to one or more of a temperature variation and a variation of the wavelength of said incident light, wherein said automatic actuator further comprises a thermal expansion element comprising an elastically deformable closed body filled with a fluid having a non-zero thermal expansion coefficient. ### Claim 4 (depends on 3) The isolator of claim 3, wherein the interior of said body is disposed in fluid communication with a reservoir filled with said fluid. ### Claim 5 (depends on 3) The isolator of claim 3, wherein said body further comprises two concentrically arranged bellows having different diameters, wherein a ring-shaped space between said two bellows is filled with said fluid. ### Claim 6 An optical isolator comprising: a polarizer adapted to polarize a beam of incident light to form a beam of polarized light; an analyzer adapted to transmit said beam of polarized light and to polarize back-reflected light; a magneto-optical element disposed between the polarizer and the analyzer, which magneto-optical element rotates the polarization direction of said beam of polarized light; a magnet generating a magnetic field penetrating said magneto-optical element; and an automatic actuator mechanically connected to said magnet to move said magnet relative to said magneto-optical element in response to one or more of a temperature variation and a variation of the wavelength of said incident light wherein said automatic actuator further comprises a thermal expansion element comprising a piston that is axially movable in a cylinder filled with a fluid having a non-zero thermal expansion coefficient. ### Claim 7 (depends on 6) The isolator of claim 6, wherein said fluid further comprises one or more of hydraulic oil, acetone, and ammonia. ### Claim 8 An optical isolator comprising: a polarizer adapted to polarize a beam of incident light to faun a beam of polarized light; an analyzer adapted to transmit said beam of polarized light and to polarize back-reflected light; a magneto-optical element disposed between the polarizer and the analyzer, which magneto-optical element rotates the polarization direction of said beam of polarized light; a magnet generating a magnetic field penetrating said magneto-optical element; and an automatic actuator mechanically connected to said magnet to move said magnet relative to said magneto-optical element in response to one or more of a temperature variation and a variation of the wavelength of said incident light wherein said automatic actuator further comprises a thermal expansion element comprising an elastically deformable closed body filled with a fluid having a non-zero thermal expansion coefficient. ### Claim 9 (depends on 8) The isolator of claim 8, wherein the interior of said body is disposed in fluid communication with a reservoir filled with said fluid. ### Claim 10 (depends on 8) The isolator of claim 8, wherein said body further comprises two concentrically arranged bellows having different diameters, wherein a ring-shaped space between said two bellows is filled with said fluid.