Extended bandwidth semiconductor optical amplifier systems and methods

Abstract

Optical devices and associated production methods are disclosed, one example of such a device takes the form of a semiconductor optical amplifier having first and second ends that at least partially define a signal propagation path. The semiconductor optical amplifier has an active layer that includes multiple quantum well stacks disposed between the first and second ends along the signal propagation path. Finally, the multiple quantum well stacks have a thickness and a width that vary along the signal propagation path.

1 . A semiconductor optical amplifier, comprising: 
 first and second ends that lie along a signal propagation path; and    an active layer that includes multiple quantum well stacks disposed between the first and second ends and comprising at least a portion of the signal propagation path, the multiple quantum well stacks having both a thickness and a width, and the multiple quantum well stacks being constructed such that both the thickness and the width vary along the signal propagation path.    
     
     
         2 . The semiconductor optical amplifier as recited in  claim 1 , wherein the thickness of the multiple quantum well stacks varies non-linearly along the signal propagation path.  
     
     
         3 . The semiconductor optical amplifier as recited in  claim 1 , wherein at least a portion of the multiple quantum well stacks has a thickness that is substantially constant.  
     
     
         4 . The semiconductor optical amplifier as recited in  claim 1 , wherein the thickness of the multiple quantum well stacks is relatively greater at a relatively narrower portion of the multiple quantum well stacks than at a relatively wider portion of the quantum well stacks.  
     
     
         5 . The semiconductor optical amplifier as recited in  claim 1 , wherein a cross-sectional area of the multiple quantum well stacks oriented in a direction substantially perpendicular to the signal propagation path is substantially constant.  
     
     
         6 . The semiconductor optical amplifier as recited in  claim 1 , wherein the multiple quantum well stacks comprise at least a portion of a mesa structure.  
     
     
         7 . The semiconductor optical amplifier as recited in  claim 6 , wherein the mesa structure has a cross-section substantially in the form of one of: a rectangle; a trapezoid; and, an inverted trapezoid.  
     
     
         8 . The semiconductor optical amplifier as recited in  claim 1 , wherein the multiple quantum well stacks comprise alternating layers of barriers and quantum wells.  
     
     
         9 . The semiconductor optical amplifier as recited in  claim 8 , wherein a thickness of the quantum wells varies along the signal propagation path.  
     
     
         10 . The semiconductor optical amplifier as recited in  claim 1 , wherein the semiconductor optical amplifier is configured to permit light to travel in either direction along the signal propagation path.  
     
     
         11 . The semiconductor optical amplifier as recited in  claim 1 , further comprising: 
 a substrate having upper and lower surfaces, the upper surface being located proximate the active layer;    a first electrode positioned proximate the lower surface of the substrate; and    a second electrode positioned above the active layer.    
     
     
         12 . An optical device, comprising: 
 a first semiconductor optical amplifier; and    a second semiconductor optical amplifier that cooperates with the first semiconductor optical amplifier to define a signal propagation path that has a middle portion and two end portions, the middle portion having a thickness different from that of either of the end portions, and each of the first and second semiconductor optical amplifiers including an active layer, the respective active layer of each semiconductor optical amplifier including multiple quantum well stacks that form a portion of the signal propagation path, the multiple quantum well stacks of each active layer having both a thickness and a width, and the multiple quantum well stacks of each active layer being constructed such that both the thickness and the width vary along the signal propagation path.    
     
     
         13 . The optical device as recited in  claim 12 , wherein the middle portion of the signal propagation path defined by the first and second semiconductor optical amplifiers is relatively thicker than the end portions.  
     
     
         14 . The optical device as recited in  claim 12 , wherein the middle portion of the signal propagation path defined by the first and second semiconductor optical amplifiers is relatively thinner than the end portions.  
     
     
         15 . The optical device as recited in  claim 12 , wherein the thickness of the multiple quantum well stacks of at least one of the active layers varies non-linearly along the signal propagation path.  
     
     
         16 . The optical device as recited in  claim 12 , wherein at least a portion of the multiple quantum well stacks of at least one of the active layers has a thickness that is substantially constant.  
     
     
         17 . The optical device as recited in  claim 12 , wherein the optical device is configured to permit light to travel in either direction along the signal propagation path.  
     
     
         18 . The optical device as recited in  claim 12 , wherein the multiple quantum well stacks of each of the active layers comprise alternating layers of barriers and quantum wells.  
     
     
         19 . The optical device as recited in  claim 18 , wherein a thickness of the quantum wells varies along the signal propagation path.  
     
     
         20 . The optical device as recited in  claim 12 , wherein the first and second semiconductor optical amplifiers abut each other.  
     
     
         21 . The optical device as recited in  claim 12 , wherein, for each active layer, the thickness of the multiple quantum well stacks is relatively greater at a relatively narrower portion of the multiple quantum well stacks than at a relatively wider portion of the quantum well stacks.  
     
     
         22 . An optical device, comprising: 
 a laser; and    semiconductor optical amplifier configured and arranged to boost a laser output, the semiconductor optical amplifier comprising:    first and second ends that lie along a signal propagation path; and    an active layer that includes multiple quantum well stacks disposed between the first and second ends and comprising at least a portion of the signal propagation path, the multiple quantum well stacks having both a thickness and a width, and the multiple quantum well stacks being constructed such that both the thickness and the width vary along the signal propagation path.    
     
     
         23 . The optical device as recited in  claim 22 , wherein the laser comprises an electroabsorption laser.  
     
     
         24 . The optical device as recited in  claim 22 , wherein the thickness of the multiple quantum well stacks is relatively greater at a relatively narrower portion of the multiple quantum well stacks than at a relatively wider portion of the quantum well stacks.  
     
     
         25 . The optical device as recited in  claim 22 , wherein the thickness of the multiple quantum well stacks varies non-linearly along the signal propagation path.  
     
     
         26 . The optical device as recited in  claim 22 , wherein at least a portion of the multiple quantum well stacks has a thickness that is substantially constant.  
     
     
         27 . The optical device as recited in  claim 22 , wherein a cross-sectional area of the multiple quantum well stacks oriented in a direction substantially perpendicular to the signal propagation path is substantially constant.  
     
     
         28 . The optical device as recited in  claim 22 , wherein the multiple quantum well stacks comprise at least a portion of a mesa structure.  
     
     
         29 . The optical device as recited in  claim 22 , wherein the semiconductor optical amplifier is configured to permit light to travel in either direction along the signal propagation path.  
     
     
         30 . An optical device, comprising: 
 an optical receiver having an input stage; and    a semiconductor optical amplifier configured and arranged for communication with the input stage of the optical receiver, the semiconductor optical amplifier comprising: 
 first and second ends that at least partially define a signal propagation path; and  
 an active layer that includes multiple quantum well stacks disposed between the first and second ends and comprising at least a portion of the signal propagation path, the multiple quantum well stacks having both a thickness and a width, and the multiple quantum well stacks being constructed such that both the thickness and the width vary along the signal propagation path.  
   
     
     
         31 . The optical device as recited in  claim 30 , wherein the thickness of the multiple quantum well stacks is relatively greater at a relatively narrower portion of the multiple quantum well stacks than at a relatively wider portion of the quantum well stacks.  
     
     
         32 . The optical device as recited in  claim 30 , wherein the thickness of the multiple quantum well stacks varies non-linearly along the signal propagation path.  
     
     
         33 . The optical device as recited in  claim 30 , wherein at least a portion of the multiple quantum well stacks has a thickness that is substantially constant.  
     
     
         34 . The optical device as recited in  claim 30 , wherein a cross-sectional area of the multiple quantum well stacks oriented in a direction substantially perpendicular to the signal propagation path is substantially constant.  
     
     
         35 . The optical device as recited in  claim 30 , wherein the multiple quantum well stacks comprise at least a portion of a mesa structure.  
     
     
         36 . The optical device as recited in  claim 30 , wherein the semiconductor optical amplifier is configured to permit light to travel in either direction along the signal propagation path.  
     
     
         37 . An optical device, comprising: 
 a first semiconductor optical amplifier; and    a second semiconductor optical amplifier that cooperates with the first semiconductor optical amplifier to define a signal propagation path of varying thickness, and each of the first and second semiconductor optical amplifiers including an active layer, the respective active layer of each semiconductor optical amplifier including multiple quantum well stacks that form a portion of the signal propagation path, the multiple quantum well stacks of the active layer of the first semiconductor optical amplifier having a variable width and relatively constant thickness along the signal propagation path, and the multiple quantum well stacks of the active layer of the second semiconductor optical amplifier having a width and thickness that vary along the signal propagation path.    
     
     
         38 . The optical device as recited in  claim 37 , wherein the first and second semiconductor optical amplifiers abut each other.  
     
     
         39 . The optical device as recited in  claim 37 , wherein, for the active layer of the second semiconductor optical amplifier, the thickness of the multiple quantum well stacks is relatively greater at a relatively narrower portion of the multiple quantum well stacks than at a relatively wider portion of the quantum well stacks.  
     
     
         40 . A method for forming a semiconductor optical amplifier, the method comprising: 
 masking a substrate so as to define an unmasked gap having a parameter whose value varies; and    growing semiconductor materials on the unmasked gap so that an active layer including at least one multiple quantum well stack is formed, the growing of the semiconductor materials being performed such that a growth rate of the semiconductor materials in the unmasked gap varies in correspondence with variations in the value of the gap parameter.    
     
     
         41 . The method as recited in  claim 40 , wherein the gap parameter comprises a width of the gap.  
     
     
         42 . The method as recited in  claim 41 , wherein the growth rate of the semiconductor materials is relatively higher in a relatively narrower portion of the unmasked gap than in a relatively wider portion of the unmasked gap.  
     
     
         43 . The method as recited in  claim 40 , wherein an MOCVD process is used to deposit the semiconductor materials on the unmasked gap.  
     
     
         44 . The method as recited in  claim 40 , wherein masking the substrate comprises: 
 depositing, on the substrate, an amorphous material nonconductive to epitaxial growth of semiconductor materials; and    patterning the amorphous materials to expose the unmasked gap.