Waveguide-coupled vertical cavity laser

Abstract

An integrated circuit includes an optical source that provides an optical signal to an optical waveguide. In particular, the optical source may be implemented by fusion-bonding a III-V semiconductor to a semiconductor layer in the integrated circuit. In conjunction with surrounding mirrors (at least one of which is other than a distributed Bragg reflector), this structure may provide a cavity with suitable optical gain at a wavelength in the optical signal along a vertical direction that is perpendicular to a plane of the semiconductor layer. For example, the optical source may include a vertical-cavity surface-emitting laser (VCSEL). Moreover, the optical waveguide, defined in the semiconductor layer, may be separated from the optical source by a horizontal gap in the plane of the semiconductor layer. During operation of the optical source, the optical signal may be optically coupled across the gap from the optical source to the optical waveguide.

What is claimed is: 
     
         1 . An integrated circuit, comprising:
 an optical source configured to provide an optical signal having a wavelength, wherein the optical source includes:
 a semiconductor layer including a region having a top surface and a bottom surface; 
 a material having a top surface and a bottom surface, wherein the bottom surface of the material is disposed on the top surface of the region, and wherein the material has an optical gain at the wavelength that is larger than that of the semiconductor layer; 
 a first mirror disposed under the bottom surface of the region, wherein the first mirror is other than a reflector that includes multiple layers with alternating indices of refraction; and 
 a second mirror disposed on the top surface of the material, wherein the first mirror, the second mirror, the region and the material define an optical cavity out of a plane of the semiconductor layer; and 
   an optical waveguide defined in the semiconductor layer.   
     
     
         2 . The integrated circuit of  claim 1 , further comprising a diffraction grating defined in the region, wherein the diffraction grating is configured to optically couple the optical signal in the plane of the semiconductor layer to the optical waveguide. 
     
     
         3 . The integrated circuit of claim  13 , wherein the diffraction grating includes an electro-optic material configured to electrically tune the wavelength of the optical source. 
     
     
         4 . The integrated circuit of  claim 1 , further comprising intra-optical-cavity electrical contacts configured to conduct charge carriers that provide a current out of the plane of the semiconductor layer in the optical source. 
     
     
         5 . The integrated circuit of  claim 1 , further comprising a layer of another material between the top surface of the region and the bottom surface of the material, wherein, during operation of the optical source, the other material restricts current out of the plane of the semiconductor layer from the semiconductor layer to the material. 
     
     
         6 . A system, comprising:
 a processor;   a memory storing a program module that is configured to be executed by the processor; and   an integrated circuit, wherein the integrated circuit includes:
 an optical source configured to provide an optical signal having a wavelength, wherein the optical source includes:
 a semiconductor layer including a region having a top surface and a bottom surface; 
 a material having a top surface and a bottom surface, wherein the bottom surface of the material is disposed on the top surface of the region, and wherein the material has an optical gain at the wavelength that is larger than that of the semiconductor layer; 
 a first mirror disposed under the bottom surface of the region, wherein the first mirror is other than a reflector that includes multiple layers with alternating indices of refraction; and 
 a second mirror disposed on the top surface of the material, wherein the first mirror, the second mirror, the region and the material define an optical cavity out of a plane of the semiconductor layer; and 
 
 an optical waveguide defined in the semiconductor layer. 
   
     
     
         7 . The system of  claim 6 , further comprising a diffraction grating defined in the region, wherein the diffraction grating is configured to optically couple the optical signal in the plane of the semiconductor layer to the optical waveguide. 
     
     
         8 . The system of  claim 7 , wherein the diffraction grating includes an electro-optic material configured to electrically tune the wavelength of the optical source. 
     
     
         9 . The integrated circuit of  claim 6 , further comprising intra-optical-cavity electrical contacts configured to conduct charge carriers that provide a current out of the plane of the semiconductor layer in the optical source. 
     
     
         10 . The integrated circuit of  claim 6 , further comprising a layer of another material between the top surface of the region and the bottom surface of the material, wherein, during operation of the optical source, the other material restricts current out of the plane of the semiconductor layer from the semiconductor layer to the material. 
     
     
         11 . A method for providing an optical signal having a wavelength, the method comprising:
 injecting charge carriers into an optical source in an integrated circuit, wherein the optical source includes an optical cavity out of a plane of a semiconductor layer in the integrated circuit, and wherein the optical cavity includes: a region in the semiconductor layer, a material disposed on a top surface of the region having an optical gain at the wavelength that is larger than that of the semiconductor layer, and mirrors below the semiconductor layer and above the material, wherein at least one of the mirrors is other than a reflector that includes multiple layers with alternating indices of refraction; and   optically coupling the optical signal produced in the optical source to an optical waveguide defined in the semiconductor layer.