Manufacturing method of optical device, optical device, manufacturing method of Faraday rotator, and optical communication system

Abstract

There are provided a manufacturing method of an optical device excellent in expediency, and a technique for stably manufacturing a high performance optical device. After a single crystal film which constitutes a Faraday rotator and can exhibit a substantially rectangular magnetic hysteresis, is obtained, the single crystal film is magnetized in a state where this single crystal film is incorporated in an optical device such as an optical isolator. By performing a magnetizing step after the Faraday rotator is incorporated in the optical device, it becomes unnecessary to discriminate between the front and back surfaces of the single crystal film, and the characteristics of the optical device are also improved.

1 . A Faraday rotator for rotating a polarization plane of incident light, comprising: 
 a flat rotator body made of a bismuth substitutional rare earth iron garnet single crystal film and including front and back surfaces opposite to each other; and    antireflection films formed on the front and back surfaces of the rotator body,    wherein formation shapes of the antireflection films are made different between the front and back surfaces.    
   
   
       2 . A Faraday rotator according to  claim 1 , wherein the formation shapes on the front and back surfaces are different from each other by not forming the antireflection film at least in the vicinity of one corner of one of the front and back surfaces.  
   
   
       3 . A Faraday rotator according to  claim 1 , wherein the formation shapes of the antireflection films on the front and back surfaces are different from each other by forming the antireflection film on the whole surface of one of the front and back surfaces and by forming the antireflection film on the other surface only in a predetermined region including a light transmission region of the Faraday rotator.  
   
   
       4 . A Faraday rotator for rotating a polarization plane of incident light, comprising: 
 a flat rotator body made of a bismuth substitutional rare earth iron garnet single crystal film and including front and back surfaces opposite to each other; and    a front/back confirmation processing part provided at a corner part or an edge part of the rotator body.    
   
   
       5 . A Faraday rotator according to  claim 4 , wherein the front/back confirmation processing part is a portion in which at least one corner part of the rotator body is chamfered.  
   
   
       6 . A Faraday rotator according to  claim 4 , wherein in the front/back confirmation processing part, all edge parts of the rotator body are subjected to round machining and a difference in the round machining is provided between the edge part belonging to the front surface of the rotator body and the edge part belonging to the back surface.  
   
   
       7 . A Faraday rotator according to  claim 4 , wherein the front/back confirmation processing part is a printed part provided in the corner part.  
   
   
       8 . A Faraday rotator according to  claim 4 , wherein the front/back confirmation processing part is a laser irradiation mark provided in the corner part.  
   
   
       9 . A Faraday rotator according to  claim 4 , wherein the front/back confirmation processing part is formed in a region other than a light transmission region of the Faraday rotator.  
   
   
       10 . A manufacturing method of a Faraday rotator for rotating a polarization plane of incident light, comprising: 
 a step (a) of obtaining a flat rotator body made of a bismuth substitutional rare earth iron garnet single crystal film and including front and back surfaces opposite to each other; and    a step (b) of forming antireflection films on the front and back surfaces of the rotator body,    wherein the antireflection films different in shape between the front and back surfaces are formed in the step (b).    
   
   
       11 . A manufacturing method of a Faraday rotator for rotating a polarization plane of incident light, comprising: 
 a step (c) of obtaining a flat rotator body made of a bismuth substitutional rare earth iron garnet single crystal film and including front and back surfaces opposite to each other; and    a step (d) of forming antireflection films on the front and back surfaces of the rotator body,    wherein after the step (c) or the step (d), a front/back confirmation processing part is formed at a corner part or an edge part of the rotator body.    
   
   
       12 . An optical isolator comprising: 
 a first polarizer on which forward direction light is incident;    a second polarizer which is disposed a predetermined distance away from the first polarizer and is opposite thereto and from which the forward direction light emerges; and    a Faraday rotator disposed between the first polarizer and the second polarizer and rotating a polarization plane of light transmitted through the first polarizer to emit the light to the second polarizer,    wherein the Faraday rotator includes:    a flat rotator body made of a bismuth substitutional rare earth iron garnet single crystal film and including front and back surfaces opposite to each other; and    antireflection films formed on the front and back surfaces of the rotator body, and    wherein formation shapes of the antireflection films are different between the front and back surfaces.    
   
   
       13 . An optical isolator comprising: 
 a first polarizer on which forward direction light is incident;    a second polarizer which is disposed a predetermined distance away from the first polarizer and is opposite thereto and from which the forward direction light emerges; and    a Faraday rotator disposed between the first polarizer and the second polarizer and rotating a polarization plane of light transmitted through the first polarizer to emit the light to the second polarizer,    wherein the Faraday rotator includes:    a flat rotator body made of a bismuth substitutional rare earth iron garnet single crystal film and including front and back surfaces opposite to each other; and    a front/back confirmation processing part provided at a corner part or an edge part of the rotator body.