Method for producing optical fiber

Abstract

The method for processing an entrance face of an optical fiber, through which a light beam is to be introduced into the optical fiber. The method includes forming a negative photoresist layer on the entrance and selectively exposing the photoresist layer located substantially above a core of the optical fiber to light introduced into the optical fiber from another end face of the optical fiber. The photoresist layer is developed to selectively remove the photoresist layer from an end face of a cladding of the optical fiber, a reflection layer is formed on the entrance face to enhance the reflectivity of the entrance face and the photoresist layer remaining on the entrance face is removed.

1 . A method for processing an entrance face of an optical fiber, through which a light beam is to be introduced into the optical fiber, the method comprising: 
 forming a negative photoresist layer on the entrance face;    selectively exposing the photoresist layer located substantially above a core of the optical fiber to light introduced into the optical fiber from another end face of the optical fiber;    developing the photoresist layer to selectively remove the photoresist layer from an end face of a cladding of the optical fiber;    forming a reflection layer on the entrance face to enhance the reflectivity of the entrance face; and    removing the photoresist layer remaining on the entrance face.    
   
   
       2 . The method according to  claim 1 , further comprising selectively exposing the photoresist layer above an outer periphery of the end face of the cladding so that an area on the end face of the cladding defined in a vicinity of the core is selectively exposed when the photoresist layer is developed.  
   
   
       3 . The method according to  claim 1 , wherein the reflection layer has a mirror surface.  
   
   
       4 . The method according to  claim 1 , wherein the reflection layer comprises metal.  
   
   
       5 . The method according to  claim 1 , further comprising obliquely cutting an end of the optical fiber before forming the negative photoresist layer on the entrance face, whereby the entrance face is inclined with respect to an optical axis of the optical fiber.  
   
   
       6 . A method for processing an entrance face of an optical fiber, through which a light beam is to be introduced into the optical fiber, the method comprising: 
 forming a photoresist layer on the entrance face;    exposing the photoresist layer located substantially above a core of the optical fiber to light introduced into the optical fiber from another end face of the optical fiber;    developing the photoresist layer to selectively remove the photoresist layer from one of an end face of the core and an end face of a cladding of the optical fiber;    processing the entrance face to form a structure that diffracts the light beam reflected by the entrance face; and    removing the photoresist layer remaining on the entrance face.    
   
   
       7 . The method according to  claim 6 , 
 wherein the photoresist layer formed on the entrance face is developed so that the cladding is exposed, and    wherein processing the entrance face includes etching the cladding so that the core protrudes from the cladding with the end face of the core being parallel with the end face of the cladding.    
   
   
       8 . The method according to  claim 7 , 
 wherein the cladding is etched so that the core protrudes from the cladding by a length less than λ/(4n), where λ represents the wavelength of the light beam reflected by the end face, and n represents a refractive index of a medium transmitting the light.    
   
   
       9 . The optical fiber according to  claim 8 , 
 wherein the core protrudes from the cladding by a length equal to λ/8n.    
   
   
       10 . The method according to  claim 6 , 
 wherein the photoresist layer formed on the entrance face is developed so that the core is exposed, and    wherein processing the entrance face includes forming an additional layer on the entrance face, the additional layer being configured for transmitting the light beam.    
   
   
       11 . The method according to  claim 10 , wherein the additional layer has a same refractive index as the core.  
   
   
       12 . The method according to  claim 6 , 
 wherein the photoresist layer formed on the entrance face is developed so that the core is exposed, and    wherein processing the entrance face includes etching the core so that the core forms a recessed area on the entrance face and so that the end face of the core is parallel with the end face of the cladding.    
   
   
       13 . The method according to  claim 6 , 
 wherein the photoresist layer formed on the entrance face is developed so that the cladding is exposed, and    wherein processing the entrance face includes forming an additional layer on the entrance face so that the core becomes a recessed area on the entrance face.    
   
   
       14 . The method according to  claim 6 , further comprising obliquely cutting an end of the optical fiber before forming the photoresist layer on the entrance face, whereby the entrance face is inclined with respect to an optical axis of the optical fiber.