Thermally isolating optical devices

Abstract

A thermo-optic device may be formed with trenches that undercut the substrate beneath the thermo-optic device. Through the removal of the underlying substrate, the heat dissipation of the thermo-optic device may be reduced. This may reduce the thermal budget of the device, reducing the power requirements for operating the device in some embodiments.

1 . A method comprising: 
 forming a thermo-optic device on a semiconductor substrate; and    removing a portion of the semiconductor substrate underneath the thermo-optic device.    
   
   
       2 . The method of  claim 1  wherein removing a portion includes using an isotropic etch.  
   
   
       3 . The method of  claim 2  including using an isotropic etch to form a first opening and forming a second opening through the first opening.  
   
   
       4 . The method of  claim 3  including forming the second opening using an anisotropic etch.  
   
   
       5 . The method of  claim 1  including forming a waveguide core on the semiconductor substrate and covering said core with an upper cladding.  
   
   
       6 . The method of  claim 5  including forming an opening through said upper cladding on either side of said core.  
   
   
       7 . The method of  claim 6  including leaving a portion of said upper cladding surrounding said core.  
   
   
       8 . The method of  claim 6  including forming a resistance heater over said upper cladding over said core.  
   
   
       9 . The method of  claim 1  including removing a portion of the semiconductor substrate on two opposed sides of said thermo-optic device.