Tunable magnet structure
View Patent ↗An axially symmetric permanent magnet structure with tunable longitudinal fields is described wherein selected radial magnet sectors in a truncated Halbach array configuration are tiltable. The tunable magnet structure is particularly useful in Faraday devices, such as Faraday rotators, Faraday mirrors, optical circulators and optical isolators.
1. A permanent magnet structure comprising:
an axially symmetric housing surrounding an axial clear aperture along a central axis;
a longitudinally magnetized axial high-strength permanent magnet surrounding the axial clear aperture within the housing;
at least one set of at least two radial magnet sectors disposed adjacent said axial magnet, the magnet sectors having radially aligned magnetization wherein inner surface magnetic poles are aligned to be the same as the pole of the adjacent surface of said axial magnet;
said housing having an outwardly tapered inner section in the region of the at least one set of radial permanent magnet sectors for allowing radial tilting of the magnet sectors; and
an endplate displaceably attached in the end of the housing and disposed abutting the at least one set of radial magnet sectors, the endplate being translatable along the central axis to effect radial tilting of the abutted adjacent radial magnet sector set into the tapered section of said housing thereby tuning the strength of longitudinally directed fields in the region in and near the axial magnet inner surface.
2. The tunable magnet structure of claim 1 further comprising:
a Faraday optical element forming a tunable Faraday rotator disposed along the central axis within the axial magnet, the Faraday optical element being responsive to the longitudinally directed fields to induce Faraday rotation of the polarization state of optical energy transmitted through the Faraday optical element.
3. The tunable magnet structure of claim 2 wherein the Faraday optical element is coupled to a fiber optic structure.
4. The tunable magnet structure of claim 2 wherein the Faraday optical element is a fiber optic structure coupled to a fiber optic structure.
5. The tunable magnet structure of claim 4 the Faraday optical element being fusion spliced to adjacent all-fiber optical elements.
6. The tunable magnet structure of claim 2 wherein the Faraday optical element is a bundle of fiber optic structures coupled to a bundle of fiber optic structures.
7. A Faraday device comprising:
an axially symmetric housing surrounding an axial clear aperture along a central axis;
a longitudinally magnetized axial high-strength permanent magnet surrounding the axial clear aperture within the housing;
a nonlinear optical element disposed in the clear aperture along the central axis within the axial magnet;
at least one set of at least two radial magnet sectors disposed adjacent said axial magnet, the magnet sectors having radially aligned magnetization wherein inner surface magnetic poles are aligned to be the same as the pole of the adjacent surface of said axial magnet;
said housing having an outwardly tapered inner section in the region of the at least one set of radial permanent magnet sectors for allowing radial tilting of the magnet sectors; and
an endplate displaceably attached in the end of the housing and disposed abutting the at least one set of radial magnet sectors, the endplate being translatable along the central axis to effect radial tilting of the abutted adjacent radial magnet sector set into the tapered section of said housing thereby tuning the strength of longitudinally directed fields in the region in and near the axial magnet inner surface.
8. The Faraday device according to claim 7 configured to be a polarization maintaining optical isolator.
9. The Faraday device according to claim 7 configured to be a polarization insensitive optical isolator.
10. The Faraday device according to claim 7 configured to be a Faraday mirror.