Optical element, manufacturing method thereof, and optical device

Abstract

A photoinduced refractive-index changing region is formed by irradiating while focusing a single beam of pulse laser light having an energy amount to cause a photoinduced change in refractive index onto a light guide of an optical element such as a lens, a mirror, a diffraction grating, a polarizer, or a wavelength filter. In the photoinduced refractive-index changing region, since the refractive index is periodically changed in one direction, of the light propagating through the optical element, only a polarized light penetrates through this photoinduced refractive-index changing region. Accordingly, the photoinduced refractive-index changing region can be functioned as a polarizer.

1 . An optical element which is fabricated by use of an optical substrate and in which a photoinduced refractive-index changing region is formed by irradiating a focused pulse laser light having an energy amount to cause a photoinduced change in refractive index.  
     
     
         2 . The optical element as set forth in  claim 1  having a light guide formed on the optical substrate, wherein the photoinduced refractive-index changing region exists in the light guide.  
     
     
         3 . The optical element as set forth in  claim 2 , wherein 
 the photoinduced refractive-index changing region exists at, at least, one of a light incident end portion, light exit end portion, and a middle portion of the light guide.    
     
     
         4 . The optical element as set forth in  claim 1 , wherein 
 the photoinduced refractive-index changing region exists at a boundary between a light guide formed on the optical substrate and a peripheral portion thereof.    
     
     
         5 . The optical element as set forth in  claim 1 , wherein 
 the photoinduced refractive-index changing region has a light focusing function to focus light propagating through the light guide, a refracting function to refract light propagating through the light guide, a reflecting function to reflect light propagating through the light guide, an optical diffracting function to diffract light propagating through the light guide, an optical attenuating function to attenuate light propagating through the light guide, a wavelength filter function to select a light with a specific wavelength propagating through the light guide, or a polarizing function to transmit a light in a specific polarizing direction propagating through the light guide.    
     
     
         6 . The optical element as set forth in  claim 1 , wherein 
 the optical element is an optical fiber, and the light guide is an optical fiber core.    
     
     
         7 . The optical element as set forth in  claim 2 , wherein 
 the light guide is a buried or protruded light guide formed on the optical substrate.    
     
     
         8 . The optical element as set forth in  claim 2 , wherein 
 the light guide is a plate-like light guide formed on the optical substrate.    
     
     
         9 . The optical element as set forth in  claim 7 , wherein 
 the light guide is branched on the optical substrate or inside the optical substrate.    
     
     
         10 . The optical element as set forth in  claim 9 , wherein 
 the photoinduced refractive-index changing region has been formed in the branched light guide.    
     
     
         11 . The optical element as set forth in  claim 9 , wherein 
 the photoinduced refractive-index changing region has been formed at a branching portion of the branched light guide.    
     
     
         12 . The optical element as set forth in  claim 2 , wherein modulating electrodes have been formed on the light guide.  
     
     
         13 . The optical element as get forth in  claim 6 , wherein 
 a plurality of optical fibers each provided with a photoinduced refractive-index changing region formed at a core end portion thereof are arranged while making the end portions contact with a reflecting member.    
     
     
         14 . The optical element as set forth in  claim 13 , wherein 
 a polarization-plane rotating element has been coupled between the end portions of the plurality of optical fibers.    
     
     
         15 . The optical element as set forth in  claim 4 , wherein 
 another optical element has been connected to a position where the photoinduced refractive-index changing region of the light guide has been formed.    
     
     
         16 . The optical element as set forth in  claim 5 , wherein the optical element is a lens.  
     
     
         17 . The optical element as set forth in  claim 1 , wherein the optical substrate is glass consisting mainly of SiO 2 .  
     
     
         18 . The optical element as set forth in  claim 1 , wherein 
 the optical substrate is an organic material of one or more selected from polyethylene terephthalate, polyacetal, polycarbonate, polyfluorocrbonate, polyamide, polyimide, silicone, polyphenylene oxide, polysulfone, polyphenylene sulfide, polybutylene terephthalate, polyarylate, polyamideimide, polyether sulfone, polyarylate, polyetherketone, polyetherimide, polymethyl methacrylate, polyacrylate, crosslinked acrylate, polysiloxane, norbornene, an epoxy resin, a phenoxy resin, triacetylcellulose, and fluorine-denatured substances of these or an organic material mixed with at least two or more of these.    
     
     
         19 . The optical element as set forth in  claim 1 , wherein 
 the optical substrate is a β-BaB 2 O 4  crystal, a LiNbO 3  crystal, a LiTaO 3  crystal, a KH 2 PO 4  crystal, a Bi 12 SiO 20  crystal, a Bi 4 Ge 3 O 12  crystal, or a quartz crystal.    
     
     
         20 . The optical element as set forth in  claim 1 , wherein 
 the photoinduced refractive-index changing region is provided by forming high-refractive-index changing regions and low-refractive-index changing regions repeatedly formed at pitches of 1 μm or less.    
     
     
         21 . A method for manufacturing an optical element comprising the steps of: 
 preparing an optical substrate made of an inorganic material, an organic material, or a crystalline material showing an electro-optic effect; and    forming a photoinduced refractive-index changing region by irradiating while focusing a pulse laser light having an energy amount to cause a photoinduced change in refractive index onto the optical substrate.    
     
     
         22 . The method for forming an optical element as set forth in  claim 21 , wherein 
 the pulse laser light has a pulse width of 10 −12  to 10 −15  seconds.    
     
     
         23 . The method for forming an optical element as set forth in  claim 21 , wherein 
 the pulse laser light has a power density of 10 8  W/cm 2  or more.    
     
     
         24 . The method for forming an optical element as set forth in  claim 21 , wherein 
 the pulse laser light has energy per one pulse of 0.1 μJ/pulse to 10 μJ/pulse.    
     
     
         25 . The method for forming an optical element as set forth in  claim 21 , wherein 
 the pulse laser light has a pulse repetition frequency of 1 Hz or more and 100 MHz or less.    
     
     
         26 . The method for forming an optical element as set forth in  claim 21 , wherein 
 the pulse laser light is a linearly polarized light.    
     
     
         27 . An optical device mounted with the optical element as set forth in  claim 1.