Optical multilayer disk, multiwavelength light source, and optical system using them

Abstract

When a wavelength of a first laser beam with which a first recording medium including a first recording layer is recorded and reproduced is indicated as λ1 (nm), a wavelength of a second laser beam with which a second recording medium including a second recording layer is recorded and reproduced as λ2 (nm), the relationship between the wavelength λ1 and the wavelength λ2 is set to be expressed by 10≦|λ1−λ2|≦120. The first recording layer has a light absorptance ratio of at least 1.0 with respect to the wavelength λ1. The light transmittance of the first recording medium with respect to the wavelength λ2 is set to be at least 30 in both the cases where the recording layer is in a crystal state and in an amorphous state. In order to record and reproduce the optical multilayer disk with the above-mentioned characteristics, a multiwavelength light source with the following configuration is used. Wavelengths of fundamental waves with different wavelengths from injection parts formed at one end of a plurality of optical waveguides, which satisfy phase matching conditions different from one another and are formed in the vicinity of the surface of a substrate, are converted simultaneously, and the first and second laser beams are emitted from emission parts formed at substantially the same position at the other end of the optical waveguides. This enables an optimum optical system for high density recording and reproduction to be obtained.

1 - 11 . (canceled)  
   
   
       12 . A method of recording and reproducing with respect to an optical information recording medium including at least two recording layers formed of a phase change material on a substrate from one side using laser beams, 
 wherein the recording layers include a first recording layer and a second recording layer from the side on which the laser beams are incident, the first recording layer is included in a first recording medium and the second recording layer is included in a second recording medium,    when a wavelength of a first laser beam with which recording and reproduction are performed with respect to the first recording medium is indicated as λ1 (nm), and a wavelength of a second laser beam with which the second recording medium is recorded and reproduced as λ2 (nm), the relationship between the wavelength λ1 and the wavelength λ2 is expressed by 10≦|80 1−λ2|≦120.    
   
   
       13 . The method of recording and reproducing with respect to an optical information recording medium according to  claim 12 , wherein the relationship between the wavelength λ1 and the wavelength λ2 is expressed by 10≦|λ1−λ2|≦50.  
   
   
       14 . The method of recording and reproducing with respect to an optical information recording medium according to  claim 12 , wherein with respect to an optical information recording medium in which the second recording medium, the first recording medium, and a protective layer are formed on the substrate sequentially and the protective layer has a thickness d1 (μm) in a range of 30≦d1≦200, recording and reproduction are performed with the first and second laser beams from a side of the protective layer.  
   
   
       15 . The method of recording and reproducing with respect to an optical information recording medium according to  claim 12 , wherein recording and reproduction are performed with respect to an optical information recording medium in which the first recording medium formed on a first substrate and the second recording medium formed on a second substrate are bonded to each other.  
   
   
       16 . The method of recording and reproducing with respect to an optical information recording medium according to  claim 12 , wherein recording and reproduction are performed with a first laser beam and a second laser beam emitted from a multiwavelength light source in which a part of an optical waveguide of a second harmonic generation element and an optical waveguide of a semiconductor laser are optically coupled.  
   
   
       17 . The method of recording and reproducing with respect to an optical information recording medium according to  claim 12 , wherein the wavelength λ1 (nm) of the first laser beam is in a range of 390≦λ1≦520.  
   
   
       18 . An optical waveguide device, comprising: 
 a substrate;    a plurality of optical waveguides formed in the vicinity of a surface of the substrate;    injection parts formed at one end of the optical waveguides; and    emission parts formed on the other end of the optical waveguides,    wherein the plurality of optical waveguides satisfy phase matching conditions different from one another, and    the emission parts of the plurality of optical waveguides are provided at substantially the same position.    
   
   
       19 . The optical waveguide device according to  claim 18 , wherein the optical waveguides have periodical polarization inversion structures.  
   
   
       20 . The optical waveguide device according to  claim 19 , wherein the optical waveguides are provided with the polarization inversion structures with different periods, respectively.  
   
   
       21 . The optical waveguide device according to  claim 18 , further comprising reflectors at parts of the optical waveguides.  
   
   
       22 . The optical waveguide device according to  claim 18 , wherein a line normal to a surface opposing the substrate in the emission parts of the optical waveguides and the surface of the substrate form an angle of about 45 degrees.  
   
   
       23 . The optical waveguide device according to  claim 18 , wherein the phase matching conditions are those with respect to second harmonics.  
   
   
       24 . The optical waveguide device according to  claim 18 , wherein the phase matching conditions are those with respect to a sum frequency.  
   
   
       25 . The optical waveguide device according to  claim 18 , wherein the optical waveguides are optically coupled partially to one another.  
   
   
       26 . An multiwavelength light source, comprising; 
 a plurality of coherent light sources with different wavelengths; and    an optical waveguide device, including a substrate, a plurality of optical waveguides formed in the vicinity of a surface of the substrate, injection parts formed at one end of the optical waveguides, and emission parts formed on the other end of the optical waveguides, the plurality of optical waveguides satisfying phase matching conditions different from one another, and the emission parts of the plurality of optical waveguides being provided at substantially the same position,    wherein the wavelengths of beams emitted from the coherent light sources are converted by the optical waveguide device.    
   
   
       27 . The multiwavelength light source according to  claim 26 , wherein the coherent light sources are semiconductor lasers and the injection parts of the optical waveguide device and the semiconductor lasers are coupled directly.  
   
   
       28 . The multiwavelength light source according to  claim 26 , wherein the coherent light sources with different wavelengths are multi-stripe semiconductor lasers formed on one substrate.  
   
   
       29 . The multiwavelength light source according to  claim 26 , wherein the coherent light sources have a function for varying wavelengths.  
   
   
       30 . The multiwavelength light source according to  claim 26 , wherein the optical waveguide device includes an electrode structure including electrodes and outputs are modulated by means of the electrodes.  
   
   
       31 . An optical system, comprising: 
 a multiwavelength light source, including a plurality of coherent light sources with different wavelengths and an optical waveguide device, the optical waveguide device including a substrate, a plurality of optical waveguides formed in the vicinity of a surface of the substrate, injection parts formed at one end of the optical waveguides, and emission parts formed on the other end of the optical waveguides, the plurality of optical waveguides satisfying phase matching conditions different from one another, the emission parts of the plurality of optical waveguides being provided at substantially the same position, and wavelengths of beams from the coherent light sources being converted by the optical waveguide device; and    a focusing optical system.    
   
   
       32 . The optical system according to  claim 31 , further comprising a wavelength filter, 
 wherein the wavelength filter separates beams from the multiwavelength light source.    
   
   
       33 . The optical system according to  claim 32 , wherein the wavelength filter separates detected lights.  
   
   
       34 . The optical system according to  claim 31 , wherein beams emitted from the multiwavelength light source are subjected to intensity modulations that are different according to their wavelengths.  
   
   
       35 - 50 . (canceled)