Single mode vertical cavity surface emitting laser

Abstract

Optoelectronic devices are disclosed, an example of which is a vertical cavity surface emitting lasers (“VCSEL”) configured to emit in a single transverse mode. One exemplary VCSEL includes a substrate with upper and lower surfaces, where a lower mirror portion is disposed upon the upper surface of the substrate. An active region of the VCSEL is bounded on one side by the lower mirror portion, and on the other side by an upper mirror portion that substantially comprises an electrically isotropic material. In addition, the VCSEL includes a substantially equipotential layer disposed on the upper mirror portion, and an insulating layer arranged between the upper mirror portion and the substantially equipotential layer and defining an aperture. Among other things, such configurations enable single, lowest order, mode operation over a range of operating currents, while also providing for suppression or elimination of higher order modes.

What is claimed is:  
     
         1 . An optoelectronic device, comprising: 
 a substrate having upper and lower surfaces;    a lower mirror portion disposed upon the upper surface of the substrate;    an active region disposed proximate the lower mirror portion;    an upper mirror portion disposed proximate the active region and substantially comprising an electrically isotropic material;    a substantially equipotential layer disposed proximate the upper mirror portion; and    an insulating layer arranged between the upper mirror portion and the substantially equipotential layer and at least partially defining an aperture.    
     
     
         2 . The optoelectronic device as recited in  claim 1 , wherein the insulating layer substantially comprises one of: an oxide; air.  
     
     
         3 . The optoelectronic device as recited in  claim 1 , wherein the substantially equipotential layer has a conductivity that is substantially greater than that of the upper mirror portion.  
     
     
         4 . The optoelectronic device as recited in  claim 1 , wherein the upper mirror portion is doped such that a product of hole concentration and mobility is substantially constant for at least part of the upper mirror portion.  
     
     
         5 . The optoelectronic device as recited in  claim 1 , wherein a thickness of the insulating layer is based at least in part upon a reflectance of the upper mirror portion as measured from the active region.  
     
     
         6 . The optoelectronic device as recited in  claim 5 , wherein the thickness of the insulating layer is substantially optimal when reflectance of the upper mirror portion, as measured from the active region, is substantially minimized.  
     
     
         7 . The optoelectronic device as recited in  claim 1 , wherein a geometry and positioning of the insulating layer are such that a nominal cavity resonance outside the aperture has a relatively longer wavelength than inside the aperture.  
     
     
         8 . The optoelectronic device as recited in  claim 1 , wherein the insulating layer comprises at least two discrete portions that cooperate to at least partially define the aperture.  
     
     
         9 . The optoelectronic device as recited in  claim 1 , wherein the insulating layer is located immediately adjacent the substantially equipotential layer.  
     
     
         10 . The optoelectronic device as recited in  claim 1 , wherein the insulating layer is spaced apart from the substantially equipotential layer.  
     
     
         11 . The optoelectronic device as recited in  claim 1 , wherein a conductivity and sheet conductance of the substantially equipotential layer are at least about an order of magnitude greater than, respectively, a conductivity and sheet conductance of the upper mirror portion.  
     
     
         12 . The optoelectronic device as recited in  claim 1 , wherein at least one of the mirror portions comprises a mirror stack.  
     
     
         13 . The optoelectronic device as recited in  claim 1 , wherein the substantially equipotential layer comprises one of: a DBR mirror; or, a doped semiconductor.  
     
     
         14 . The optoelectronic device as recited in  claim 1 , further comprising: 
 first and second upper contact portions disposed on the substantially equipotential layer and collectively defining a span; and    a bottom contact portion disposed on the lower surface of the substrate.    
     
     
         15 . The optoelectronic device as recited in  claim 14 , wherein a relationship of the span to the aperture is one of: the span is larger than the aperture; or, the span is smaller than the aperture.  
     
     
         16 . The optoelectronic device as recited in  claim 1 , further comprising a dielectric stack mode control structure disposed upon the substantially equipotential layer.  
     
     
         17 . The optoelectronic device as recited in  claim 1 , wherein the dielectric stack mode control structure comprises: 
 a first dielectric layer disposed on the substantially equipotential layer; and    a second dielectric layer disposed on the first dielectric layer, a combined thickness of the first and second dielectric layers being a multiple of one quarter of a wavelength of light sourced by the optoelectronic device.    
     
     
         18 . The optoelectronic device as recited in  claim 1 , wherein the lower mirror portion is substantially formed of an n-type material and the upper mirror portion is substantially formed of a p-type material.  
     
     
         19 . The optoelectronic device as recited in  claim 1 , wherein the lower mirror portion is substantially formed of a p-type material and the upper mirror portion is substantially formed of an n-type material.  
     
     
         20 . The optoelectronic device as recited in  claim 1 , wherein both the lower mirror portion and the upper mirror portion are substantially formed of one of: an n-type material; or, a p-type material.  
     
     
         21 . The optoelectronic device as recited in  claim 1 , wherein the active region includes a plurality of p-n junctions separated from each other by a tunnel junction.  
     
     
         22 . The optoelectronic device as recited in  claim 1 , wherein the upper mirror portion includes regions of relatively higher and lower mobility, the regions of relatively higher mobility being more heavily doped than the regions of relatively lower mobility.  
     
     
         23 . The optoelectronic device as recited in  claim 1 , wherein the upper mirror portion includes a plurality of semiconductor layers having interfaces therebetween, the interfaces being relatively more heavily doped than selected non-interface regions.  
     
     
         24 . The optoelectronic device as recited in  claim 1 , further comprising at least one heat conduction layer arranged between the substrate and the substantially equipotential layer.  
     
     
         25 . The optoelectronic device as recited in  claim 24 , wherein the at least one heat conduction layer comprises: 
 a first heat conduction layer disposed on one side of the active region; and    a second heat conduction layer disposed on another side of the active region.    
     
     
         26 . A vertical cavity surface emitting laser (VCSEL), comprising: 
 a substrate having upper and lower surfaces;    a lower mirror portion disposed upon the substrate;    an active region disposed above the lower mirror portion;    an upper mirror portion disposed above the active region and substantially comprising an electrically isotropic material;    a substantially equipotential layer disposed upon the upper mirror portion;    at least one heat conduction layer arranged between the substrate and the substantially equipotential layer; and    an insulating layer arranged between the upper mirror portion and the substantially equipotential layer and at least partially defining an aperture.    
     
     
         27 . The VCSEL as recited in  claim 26 , wherein the at least one heat conduction layer comprises: 
 a first heat conduction layer situated on one side of the active region; and    a second heat conduction layer situated on another side of the active region.    
     
     
         28 . The VCSEL as recited in  claim 26 , wherein the at least one heat conduction layer is periodically doped.  
     
     
         29 . The VCSEL as recited in  claim 26 , wherein periodic doping of the at least one heat conduction layer comprises doping relatively more heavily in nulls of an electric field than in peaks of the electric field.  
     
     
         30 . The VCSEL as recited in  claim 26 , wherein the active region comprises: 
 a lower p-n junction layer proximate the lower mirror portion;    a first tunnel junction disposed upon the lower p-n junction layer;    an upper p-n junction layer disposed upon the first tunnel junction; and    a second tunnel junction disposed upon the upper p-n junction layer.    
     
     
         31 . The VCSEL as recited in  claim 30 , wherein at least one of the following comprises a plurality of quantum wells: the lower p-n junction layer; and, the upper p-n junction layer.  
     
     
         32 . The VCSEL as recited in  claim 26 , wherein the insulating layer comprises at least two discrete portions that cooperate to at least partially define the aperture.  
     
     
         33 . The VCSEL as recited in  claim 26 , wherein the lower mirror portion comprises a semiconductor mirror stack having a plurality of mirror pairs of alternating high and low, relative to each other, refractive indexed material.  
     
     
         34 . The VCSEL as recited in  claim 33 , wherein the mirrors of the semiconductor mirror stack comprise DBR mirrors substantially comprising one of: AlGaAs; or, AlInGaAsPSb lattice matched to InP.  
     
     
         35 . The VCSEL as recited in  claim 26 , wherein at least a portion of an edge of the aperture is tapered at an electric field null.  
     
     
         36 . The VCSEL as recited in  claim 26 , wherein the at least one heat conduction layer substantially comprises an n-type material.  
     
     
         37 . The VCSEL as recited in  claim 26 , wherein the substantially equipotential layer substantially comprises AlGaAs.  
     
     
         38 . The VCSEL as recited in  claim 26 , further comprising: 
 first and second upper contact portions disposed on the substantially equipotential layer and collectively defining a span; and    a bottom contact portion disposed on the lower surface of the substrate.