Single mode vertical cavity surface emitting laser using photonic crystals with a central defect

Abstract

Vertical cavity surface emitting lasers are disclosed, one example of which includes a substrate upon which a lower mirror layer is formed. An active region and upper mirror layer are disposed, in that order, on the lower mirror layer. In particular, the upper mirror layer includes a plurality of DBR layers formed on the active region. The upper mirror layer additionally includes a photonic crystal formed on the plurality of DBR layers and having a periodic structure that contributes to the definition of a central defect. As a consequence of this structure, the photonic crystal has a reflectivity that is wavelength dependent, and the central defect enables the VCSEL to propagate a single mode.

1 . A vertical cavity surface emitting laser, comprising: 
 a lower mirror layer formed on a substrate;    an active region formed on the lower mirror layer; and    an upper mirror layer formed on the active region, the upper mirror layer comprising: 
 a plurality of DBR layers; and  
 a photonic crystal formed on the plurality of DBR layers and having a periodic structure that at least partially defines a central defect.  
   
     
     
         2 . The vertical cavity surface emitting laser as recited in  claim 1 , wherein the photonic crystal cooperates with the plurality of DBR layers to facilitate substantially single mode lasing of the vertical cavity surface emitting laser.  
     
     
         3 . The vertical cavity surface emitting laser as recited in  claim 1 , wherein the central defect defines at least one hole.  
     
     
         4 . The vertical cavity surface emitting laser as recited in  claim 1 , wherein the central defect is substantially free of holes.  
     
     
         5 . The vertical cavity surface emitting laser as recited in  claim 1 , wherein the periodic structure of the photonic crystal comprises a periodic pattern of holes defined by the photonic crystal.  
     
     
         6 . The vertical cavity surface emitting laser as recited in  claim 5 , wherein at least one of the holes extends completely through the photonic crystal.  
     
     
         7 . The vertical cavity surface emitting laser as recited in  claim 5 , wherein at least one of the holes extends at least into the active region.  
     
     
         8 . The vertical cavity surface emitting laser as recited in  claim 5 , wherein at least one of the holes extends at least into the plurality of DBR layers.  
     
     
         9 . The vertical cavity surface emitting laser as recited in  claim 5 , wherein at least one of the holes extends at least into the lower mirror layer.  
     
     
         10 . The vertical cavity surface emitting laser as recited in  claim 5 , wherein the holes of the periodic structure of the photonic crystal are filled with air.  
     
     
         11 . The vertical cavity surface emitting laser as recited in  claim 5 , wherein the holes of the periodic structure of the photonic crystal have substantially the same depth.  
     
     
         12 . The vertical cavity surface emitting laser as recited in  claim 5 , wherein the depth of the holes of the periodic structure of the photonic crystal varies.  
     
     
         13 . The vertical cavity surface emitting laser as recited in  claim 1 , wherein the lower mirror layer comprises at least one of: a plurality of DBR layers; and, a photonic crystal having a periodic structure.  
     
     
         14 . The vertical cavity surface emitting laser as recited in  claim 1 , wherein the periodic structure of the photonic crystal corresponds with a particular reflectivity of the photonic crystal.  
     
     
         15 . The vertical cavity surface emitting laser as recited in  claim 1 , wherein the active region includes a plurality of quantum wells.  
     
     
         16 . The vertical cavity surface emitting laser as recited in  claim 1 , wherein the upper mirror layer comprises an additional photonic crystal having a periodic structure.  
     
     
         17 . The vertical cavity surface emitting laser as recited in  claim 1 , wherein a semi-insulating region is formed in the active region.  
     
     
         18 . The vertical cavity surface emitting laser as recited in  claim 17 , wherein a hole of the periodic structure of the photonic crystal extends through the semi-insulating region so that a semi-insulating ring is formed in the active region.  
     
     
         19 . The vertical cavity surface emitting laser as recited in  claim 1 , wherein the periodic structure is two dimensional.  
     
     
         20 . The vertical cavity surface emitting laser as recited in  claim 1 , wherein the periodic structure is three dimensional.  
     
     
         21 . The vertical cavity surface emitting laser as recited in  claim 1 , wherein the central defect facilitates propagation of a single mode from the vertical cavity surface emitting laser.  
     
     
         22 . A vertical cavity surface emitting laser, comprising: 
 a substrate;    a lower mirror layer formed on the substrate and comprising a first photonic crystal having a periodic structure;    an active region formed on the lower mirror layer; and    an upper mirror layer formed on the active region and comprising a second photonic crystal having a periodic structure that at least partially defines a central defect.    
     
     
         23 . The vertical cavity surface emitting laser as recited in  claim 22 , wherein the central defect of the second photonic crystal defines at least one hole.  
     
     
         24 . The vertical cavity surface emitting laser as recited in  claim 23 , wherein the at least one hole defined by the central defect of the second photonic crystal corresponds to a particular polarization state.  
     
     
         25 . The vertical cavity surface emitting laser as recited in  claim 22 , wherein the central defect of the second photonic crystal is substantially free of holes.  
     
     
         26 . The vertical cavity surface emitting laser as recited in  claim 22 , wherein the periodic structure of each of the first and second photonic crystals comprises a periodic pattern of holes defined by, respectively, the first and second photonic crystals.  
     
     
         27 . The vertical cavity surface emitting laser as recited in  claim 26 , wherein at least one hole of the periodic structure of the second photonic crystal extends at least part way into the second photonic crystal.  
     
     
         28 . The vertical cavity surface emitting laser as recited in  claim 26 , wherein at least one hole of the periodic structure of the second photonic crystal extends past the second photonic crystal.  
     
     
         29 . The vertical cavity surface emitting laser as recited in  claim 22 , wherein at least one of the first and second photonic crystals comprises a plurality of DBR layers.  
     
     
         30 . The vertical cavity surface emitting laser as recited in  claim 22 , wherein the periodic structure of the second photonic crystal corresponds with a particular reflectivity of the second photonic crystal.  
     
     
         31 . The vertical cavity surface emitting laser as recited in  claim 22 , wherein the active region includes a plurality of quantum wells.  
     
     
         32 . The vertical cavity surface emitting laser as recited in  claim 22 , wherein a semi-insulating region is formed in the active region.  
     
     
         33 . The vertical cavity surface emitting laser as recited in  claim 22 , wherein at least one of the following is two dimensional: the periodic structure of the first photonic crystal; and, the periodic structure of the second photonic crystal.  
     
     
         34 . The vertical cavity surface emitting laser as recited in  claim 22 , wherein at least one of the following is three dimensional: the periodic structure of the first photonic crystal; and, the periodic structure of the second photonic crystal.  
     
     
         35 . The vertical cavity surface emitting laser as recited in  claim 22 , wherein at least one of the first and second photonic crystals substantially comprises a material having a tunable refractive index.  
     
     
         36 . The vertical cavity surface emitting laser as recited in  claim 22 , wherein the upper mirror layer further comprises a plurality of DBR layers interposed between the active region and the second photonic crystal.  
     
     
         37 . The vertical cavity surface emitting laser as recited in  claim 22 , wherein the central defect of the second photonic crystal facilitates propagation of a single mode from the vertical cavity surface emitting laser.