Ex parte KOMATSU - Page 7




          Appeal No. 1997-4033                                                        
          Application No. 08/589,584                                                  


               Claim 22, the only independent claim, reads as follows:                
               22.  A Mach-Zehnder optical modulator having first and                 
          second passive regions and an active region between said first              
          and second passive regions, said Mach-Zehnder optical                       
          modulator comprising:                                                       
               a semiconductor substrate extending over said first and                
          second passive regions and said active region;                              
               a bottom electrode extending on an entire part of a                    
          bottom surface of said semiconductor substrate;                             
               a first cladding layer extending on an entire part of a                
          top surface of said semiconductor substrate;                                
               a ridge-shaped optical wave-guide having: a Y-shaped                   
          branching passive wave-guide section on said first passive                  
          regions [sic, region]; a Y-coupling passive wave-guide section              
          on said second passive regions [sic, region]; and two parallel              
          straight phase modulator sections on said active region;                    
          wherein said ridge-shaped optical wave-guide comprises:                     
               a buffer layer provided on said first cladding layer;                  
               a multiple quantum well optical wave-guide layer provided              
          on said buffer layer, said multiple quantum well optical wave-              
          guide                                                                       
          layer being grown by a metal organic vapor phase epitaxy using              
          dielectric stripe masks having a large width in said active                 
          region and a small width in said first and second passive                   
          regions so that said multiple quantum well optical wave-guide               
          layer provided on said first and second passive regions has a               
          thickness larger than that provided on said active region and               
          so that said multiple quantum well optical wave-guide layer                 
          provided on said first and second passive regions has a band                
          gap wavelength smaller than that provided on said active                    
          region;                                                                     
               a second cladding layer provided on said multiple quantum              
          well optical wave-guide layer;                                              

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