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BR-102021021603-B1 - Optical Circulator

BR102021021603B1BR 102021021603 B1BR102021021603 B1BR 102021021603B1BR-102021021603-B1

Abstract

OPTICAL CIRCULATOR. The invention in question relates to an optical circulator capable of functioning without external magnetization. To this end, the said optical circulator has its structure made of a magneto-optical material based on an iron garnet with reduced saturation magnetization that does not require an external magnetizing element (permanent magnet or electromagnet) to maintain its saturated magnetization state. The said magneto-optical material comprises an alloy of iron garnet, bismuth and europium, with the molecular formula BiX(EuZHo1Z)3-XFe5-YGaYO12.

Inventors

  • GIANNI MASAKI TANAKA PORTELA
  • Miguel Levy
  • HUGO ENRIQUE HERNÁNDEZ FIGUEROA

Assignees

  • MCHIGAN TECHNOLOGICAL UNIVERSITY
  • UNIVERSIDADE ESTADUAL DE CAMPINAS - UNICAMP

Dates

Publication Date
20260317
Application Date
20211027

Claims (3)

  1. 1. Optical circulator comprising a base (5) made of magneto-optical material; said base (5) comprising a plurality of through holes (2) symmetrically arranged in a triangular network (21) provided with three waveguides (3), and a resonant cavity (7); said resonant cavity (7) being integrated by the combination of a central hole of circular area, an annular wall (42), a first circular formation of through holes (23) and a second circular formation of through holes (22), the annular wall (42) disposed inside the central hole defining, therein, an internal circular area (41) and an external ring (43); said optical circulator (1) being characterized in that: said magneto-optical material of the base (5) comprises an alloy of iron, bismuth and europium garnet, of molecular formula Bix(EuzHoi-z)3-xFe5-YGaYOi2; said wall The ring (42) is made of magneto-optical alloy of iron, bismuth and europium garnet, with molecular formula Bix(EuzHoi-z)3-xFe5-YGaYOi2; and said optical circulator (1) is applicable in optical communication systems operating at wavelengths between 1550.1137 nm and 1550.1537 nm.
  2. 2. Optical circulator, according to claim 1, characterized in that, in the molecular formula Bix(EuzHoi-z)3-xFe5-YGaYθi2, X equals 1.22; Z equals 0.45; and Y equals 0.956, achieving the composition Bi1.22(Eu0.45Ho0.55)1.78Fe4.044Ga0.956O12 with eight formula units per unit cell of the crystal.
  3. 3. Optical circulator, according to1, characterized by the base faces having at least one layer (6) of perfect material or high impedance material

Description

FIELD OF THE INVENTION [001] The invention in question relates to an externally magnetized optical circulator based on an iron garnet with reduced saturation magnetization, which comprises a compact, three-port structure built from the creation of a photonic crystal structure in an iron garnet with reduced saturation magnetization that does not require the use of an external magnetic field to maintain the saturated magnetization state. [002] The object of the present invention is situated in the area of optical communication systems and, more particularly, in the area of optical circuits with high density of component integration. Consequently, the object of the present invention is an optical signal guide structure. FUNDAMENTALS OF THE INVENTION [003] Optical circulators comprise devices capable of directing, with low insertion losses, optical signals present at one of their ports (input port) to an additional port (output port), while protecting the source of the optical signals connected to the input port against parasitic or unwanted reflections in an optical circuit composed of several components. In a 3-port optical circulator, for example, the input optical signals present at ports 1, 2, and 3 are transferred, with low insertion losses, to ports 2, 3, and 1, respectively, without these optical signals being reflected back to the source port. Optical circulators can also be used in optical communication systems to separate optical signals traveling in opposite directions in an optical fiber to achieve bidirectional transmission in a single fiber. [004] It is also known to those skilled in the art that the operation of an optical circulator is normally linked to an external magnetic field, which can be generated from a permanent magnet or electromagnet. [005] Patent document BR1020150109610, for example, describes a three-port optical circulator in the shape of a fork based on a two-dimensional photonic crystal with a triangular lattice whose operation depends on the application of an external magnetic field. In a rather particular way, the optical circulator described in this patent document is able to promote the non-reciprocal transmission of optical signals in clockwise and counterclockwise directions depending on the direction of the external magnetic field. As cited in the aforementioned patent document BR1020150109610, optical circulators whose operation is linked to an external magnetic field are also described in patent documents US20120251048, CN104101947 and US20120243844, the latter describing, in a rather particular way, a three-port optical circulator which, specially adapted to operate at a wavelength of 2,841 μm (2841 nm), is made on a dielectric substrate in which air columns are defined symmetrically arranged in the form of a triangular lattice and a centrally arranged magneto-optical cavity. [006] Although optical circulators belonging to the current state of the art are reasonably functional, it should be noted that they cannot be materialized on micrometric or nanometric scales for applications in optical circuits with very high component integration density. After all, the requirement for devices used to create the necessary external magnetic fields, which may employ permanent magnets or bulky electromagnets, implies the materialization of large-sized optical circulators. [007] On the other hand, as described in patent document US6770223, the current state of the art also describes a magneto-optical material that, especially intended for the manufacture of optical devices (optical circulators, optical switches and other non-reciprocating optical devices) operating at a wavelength of 1550 nm, provides autonomous maintenance of its saturated magnetization state without the need for an external magnetic field and, therefore, without the need for an external device integrated by a permanent magnet or electromagnet. The aforementioned magneto-optical material is fundamentally composed of an iron-bismuth garnet alloy, with the addition of europium. Thus, it is extremely important to emphasize that the object of patent document US6770223 is not immediately applicable to any design of any optical circulator. [008] However, the aforementioned patent document US6770223, in addition to specifying the limitation of application to optical devices operating at a wavelength of 1550 nm, does not reveal any specific design or set of specific constructive characteristics of optical devices made of an iron-bismuth garnet alloy with the addition of europium and, for this reason, does not present optimized and/or synergistic solutions capable of combining the autonomous maintenance of its saturated magnetization state with optical circulators whose gyrotropy of the magneto-optical material is optimized in order to maximize the bandwidth of the device. [009] It is based on this scenario that the invention in question arises. BRIEF DESCRIPTION OF THE INVENTION [0010] The invention relates to an optical