Mirror structure for reducing the effect of feedback on a VCSEL

Abstract

An exemplary embodiment of the present invention integrates an absorbing layer into the emitting mirror of a VCSEL to reduce the reflectivity of the emitting mirror as seen by the feedback optical wave. The absorbing layer may be made of a suitable semiconductor material, such as a GaAs layer in a laser emitting near 850 nm or highly doped p-layer, and may disposed epitaxially in a semiconductor or metamorphic mirror. Alternatively, a metal layer may be disposed in the dielectric portion of a hybrid mirror or all-dielectric mirror.

1 - 24 . (canceled)  
     
     
         25 . A method for reducing external feedback in a vertical cavity surface emitting laser (VCSEL), comprising: 
 determining optimum thickness of at least one of a plurality of high index layers in a first emitting mirror of a first VCSEL in accordance with air side reflectivity of said first VCSEL;    determining optimum thickness of an absorbing layer in a second emission mirror of a second VCSEL in accordance with air side reflectivity of said second VCSEL using said optimum thickness of said high index layers; and    determining optimum thickness of at least one of a plurality of low index of refraction layers in a third emission mirror of a third VCSEL in accordance with air side reflectivity of said third VCSEL using said optimum thickness of said high index layers and said optimum thickness of said absorbing layer.    
     
     
         26 . A method for reducing external feedback in a vertical cavity surface emitting laser (VCSEL), comprising: 
 determining optimum thickness of at least one of a plurality of high-index layers in a first emitting mirror in accordance with air-side reflectivity of the VCSEL;    determining optimum thickness of an absorbing layer in a second emission mirror in accordance with air-side reflectivity of the VCSEL using the optimum thickness of the high-index layers; and    determining optimum thickness of at least one of a plurality of low-index of refraction layers in a third emission mirror in accordance with air-side reflectivity of the VCSEL using the optimum thickness of the high-index layers and the optimum thickness of the absorbing layer.    
     
     
         27 . A method for constructing a vertical cavity surface emitting laser (VCSEL) with minimal external feedback, comprising: 
 setting the thickness of an absorbing layer to isolate external and internal cavities of the VCSEL;    reducing air-side reflectivity as a function of thickness of high-index layers at an emitting facet of the VCSEL;    reducing air-side reflectivity as a function of thickness of the absorbing layer of the VCSEL;    reducing air-side reflectivity as a function of thickness of the low-index layers at the emitting facet of the VCSEL.    
     
     
         28 . A method of constructing a vertical cavity surface emitting laser (VCSEL) comprising: 
 depositing a plurality of layers to form a first mirror;    forming a optical cavity adjacent to the first mirror;    depositing a plurality of layers to form a second mirror adjacent to the optical cavity, wherein one of the layers is an absorbing layer;    said absorbing layer is located at or near a standing optical wave pattern in closest proximity to an emission facet so as to minimally interact with transmission light in the optical cavity, and further so as to strongly interact with external light reflected back into the optical cavity.    
     
     
         29 . The method of  claim 28 , wherein the layers of the first mirror are formed of alternating layers having a low index of refraction and layers having a high index of refraction.  
     
     
         30 . The method of claims  28 , wherein the layers of the second mirror, excluding the absorbing layer, are formed of alternating layers having a low index of refraction and layers having a high index of refraction.  
     
     
         31 . The method of  claim 28 , wherein the first mirror is a semiconductor mirror.  
     
     
         32 . The method of  claim 28 , wherein the first mirror is a dielectric mirror.  
     
     
         33 . The method of  claim 28 , wherein the second mirror is a semiconductor mirror.  
     
     
         34 . The method of  claim 28 , wherein the second mirror is a dielectric mirror.  
     
     
         35 . The method of  claim 28 , further comprising the step of forming an aperture between the optical cavity and the second mirror, before the layers of the second mirror are deposited.  
     
     
         36 . The method of  claim 35 , wherein the second mirror comprises a first part and a second part; wherein the first part is formed adjacent to the aperture and the second part is formed adjacent to the first part.  
     
     
         37 . The method of  claim 36 , wherein a current constriction having a constriction aperture is formed within the first part of the second mirror.  
     
     
         38 . The method of  claim 37 , wherein the absorbing layer is deposited within the first part of the second mirror at a point within the confines of the constriction aperture.  
     
     
         39 . The method of  claim 36 , wherein the first part is a semiconductor mirror.  
     
     
         40 . The method of claims  36 , wherein the second part is a dielectric mirror.  
     
     
         41 . A method of constructing a vertical cavity surface emitting laser (VCSEL) comprising: 
 depositing a plurality of layers to form a first mirror;    forming a optical cavity adjacent to the first mirror;    forming an aperture adjacent to the optical cavity;    depositing a plurality of layers to form a second mirror adjacent to the aperture, wherein one of the layers is an absorbing layer;    said absorbing layer is located at or near a standing optical wave pattern in closest proximity to an emission facet so as to minimally interact with transmission light in the optical cavity, and further so as to strongly interact with external light reflected back into the optical cavity.    
     
     
         42 . The method of  claim 41  wherein the layers of the first mirror are formed of alternating layers having a low index of refraction and layers having a high index of refraction.  
     
     
         43 . The method of claims  41  wherein the layers of the second mirror, excluding the absorbing layer, are formed of alternating layers having a low index of refraction and layers having a high index of refraction.  
     
     
         44 . The method of  claim 41 , wherein the first mirror is a semiconductor mirror.  
     
     
         45 . The method of  claim 41 , wherein the first mirror is a dielectric mirror.  
     
     
         46 . The method of  claim 41 , wherein the second mirror is a semiconductor mirror.  
     
     
         47 . The method of  claim 41 , wherein the second mirror is a dielectric mirror.  
     
     
         48 . The method of  claim 41 , wherein the second mirror comprises a first part and a second part; wherein the first part is formed within the aperture and the second part is formed adjacent to the first part and aperture.  
     
     
         49 . The method of  claim 48 , further comprising the step of forming a current constriction having a constriction aperture with the first part of the second mirror.  
     
     
         50 . The method of  claim 49 , wherein the absorbing layer is deposited within the second mirror at a point within the first part of the second mirror and within the constriction aperture.  
     
     
         51 . The method of  claim 48 , wherein the first part is a semiconductor mirror.  
     
     
         52 . The method of claims  48 , wherein the second part is a dielectric mirror.  
     
     
         53 . A method of constructing a vertical cavity surface emitting laser (VCSEL) comprising: 
 depositing a plurality of layers to form a first mirror;    forming a optical cavity adjacent to the first mirror;    forming an aperture adjacent to the optical cavity;    forming a current constriction having a constriction aperture adjacent to the aperture;    depositing a plurality of layers to form a second mirror adjacent to the current constriction, wherein one of the layers is an absorbing layer;    said absorbing layer is located at or near a standing optical wave pattern in closest proximity to an emission facet so as to minimally interact with transmission light in the optical cavity, and further so as to strongly interact with external light reflected back into the optical cavity.    
     
     
         54 . The method of  claim 53 , wherein the layers of the first mirror alternate between layers having a low index of refraction and layers having a high index of refraction.  
     
     
         55 . The method of claims  53 , wherein the layers of the second mirror, excluding the absorbing layer, are formed of alternating layers having a low index of refraction and layers having a high index of refraction.  
     
     
         56 . The method of  claim 53 , wherein the first mirror is a semiconductor mirror.  
     
     
         57 . The method of  claim 53 , wherein the first mirror is a dielectric mirror.  
     
     
         58 . The method of  claim 53 , wherein the second mirror is a semiconductor mirror.  
     
     
         59 . The method of  claim 53 , wherein the second mirror is a dielectric mirror.  
     
     
         60 . The method of  claim 53 , wherein the second mirror comprises a first part and a second part; wherein the first part is formed within the constriction aperture and the second part is formed adjacent to the first part and current constriction.  
     
     
         61 . The method of  claim 60 , wherein the absorbing layer is deposited within the second mirror at a point within the first part of the second mirror and within the constriction aperture.  
     
     
         62 . The method of  claim 60 , wherein the first part is a semiconductor mirror.  
     
     
         63 . The method of claims  60 , wherein the second part is a dielectric mirror.