High Efficiency, Wavelength Stabilized Laser Diode Using AWG's And Architecture For Combining Same With Brightness Conservation

Abstract

The invention relates to high power semiconductor lasers based on a laser diode array waveguide grating (DAWG) in which the wavelength is stabilized using an array waveguide grating (AWG) in an external cavity configuration. Another aspect of the present invention relates to techniques for efficiently coupling optical gain element arrays to an AWG. Another feature provides for the efficient and brightness-conserving combination of multiple high power DAWG lasers into a single output.

1 . A high power laser source comprising: 
 a first chip including a multi-mode semiconductor waveguide for providing gain in a predetermined wavelength band, wherein each semiconductor waveguide has a first reflector at one end;    a second chip including an array waveguide grating having an input port coupled to the semiconductor waveguide, and an output port;    a second reflector disposed to receive light from the array waveguide grating output port and to reflect a portion of the light back into the array waveguide grating, thereby defining a laser cavity with the first reflector;    wherein:    the semiconductor waveguide is dimensioned to support propagation of multiple transverse modes of light having wavelengths in the predetermined wavelength band; and the multiple transverse modes on the first chip are optically coupled to the input port of the array waveguide grating on the second chip.    
     
     
         2 . The high power laser source in  claim 1 , further comprising additional semiconductor waveguides, wherein spaces between the semiconductor waveguides are not uniform in order to obtain a prescribed temperature gradient across the first chip.  
     
     
         3 . The high power laser source in  claim 2 , wherein the prescribed temperature gradient is constant.  
     
     
         4 . The high power laser source in  claim 2 , wherein the prescribed temperature gradient is approximately zero.  
     
     
         5 . The high power laser source in  claim 1 , further comprising coupling means for coupling the semiconductor waveguide to the array waveguide grating, wherein the coupling means is selected from the group consisting of a planar lens, a cylindrical lens, a two-dimensional lens, a multi-mode interference region, an integrated fast-axis lens etched into the first chip, and an integrated fast-axis lens etched into the second chip.  
     
     
         6 . The high power laser source in  claim 1 , wherein the second reflector is located proximate to the output port of the array waveguide grating.  
     
     
         7 . The high power laser source in  claim 1 , wherein the second reflector is located in an output optical fiber which is coupled to the output port of the array waveguide grating.  
     
     
         8 . The high power laser source in  claim 1 , further comprising coupling means for coupling the semiconductor waveguide to the array waveguide grating, wherein the coupling means comprises a planar grin lens integrated in the input port of the array waveguide grating.  
     
     
         9 . The high power laser source in  claim 1 , wherein the semiconductor waveguide has a flare increasing in width toward the input port of the array waveguide grating.  
     
     
         10 . The high power laser source in  claim 9 , wherein the flares overlap to form a contiguous region at the input port of the array waveguide grating.  
     
     
         11 . The high power laser source in  claim 1 , wherein the semiconductor waveguide is optically coupled to a star-coupler region of the input port of the array waveguide grating.  
     
     
         12 . The high power laser source in  claim 1 , wherein the output port of the array waveguide grating comprises a single-mode output waveguide.  
     
     
         13 . The high power laser source in  claim 1 , wherein the input port of the array waveguide grating comprises a slab waveguide.  
     
     
         14 . The high power laser source in  claim 1 , wherein the input port of the array waveguide grating comprises a star-coupler region of an array waveguide grating.  
     
     
         15 . The high power laser source in  claim 5 , wherein the multi-mode interference region supports multiple wavelengths.  
     
     
         16 . The high power laser source in  claim 1 , wherein the output port of the array waveguide grating has a focus outside an edge of the second chip to reduce optical field intensity within the second chip and to provide optical coupling to an optical fiber.  
     
     
         17 . The high power laser source according to  claim 12 , further comprising additional array waveguide gratings, wherein each array waveguide grating transmits therethrough a different wavelength band and the single-mode output waveguides are combined in a wavelength combiner into a single-mode combined output waveguide which is coupled to a single-mode fiber.  
     
     
         18 . The high power laser source according to  claim 12 , further comprising additional array waveguide gratings, wherein each single-mode output waveguide is terminated at an edge of the second chip for coupling to a multi-mode core of a single output fiber.  
     
     
         19 . The high power laser source according to  claim 18 , wherein the single-mode output waveguides form a two-dimensional array at the edge of the second chip.  
     
     
         20 . The high power laser source according to  claim 18 , wherein each single-mode output waveguide is terminated at the edge of the second chip for coupling to a rectangular multi-mode core of a single output fiber.  
     
     
         21 . The high power laser source according to  claim 12 , wherein the single-mode output waveguides are terminated at an edge of the second chip to align with single-mode fibers at a first end of a single-mode fiber array.  
     
     
         22 . The high power laser source according to  claim 21 , wherein a second end of the single-mode fiber array is configured so that the single mode fibers form a two-dimensional array for coupling into a multi-mode core of a single optical fiber.