Wavelength Stabilized Diode Laser

Abstract

A hybrid external cavity laser and a method for configuring the laser having a stabilized wavelength is disclosed. The laser comprises a semiconductor gain section and a volume Bragg grating, wherein a laser emission from the semiconductor gain section is based on a combination of a reflectivity of a front facet of the semiconductor gain section and a reflectivity of the volume Bragg grating and the reflectivity of the semiconductor gain section and the volume Brag grating are insufficient by themselves to support the laser emission. The hybrid cavity laser further comprises an etalon that provides further wavelength stability.

1 . A device configured to generate at least one laser emission, the device comprising:
 a semiconductor gain section generating a light emission, said semiconductor gain section comprising:   a rear facet having a first reflectivity; and   a front facet having a second reflectivity, said rear facet and said front facet forming a first resonant cavity having a first plurality of non-lasing resonance, and   a volume Bragg grating, having a known reflectivity, configured to:
 receive said light emission; and 
 reflect a portion of the received light emission back into the semiconductor gain section, wherein the rear facet of the semiconductor gain section and the volume Bragg grating form a second resonant cavity, overlapping the first resonant cavity, said second resonant cavity generating a second plurality of non-lasing resonances, wherein at least one of said first plurality of non-lasing resonances and a corresponding at least one of said second plurality of non-lasing is substantially coincident, said substantially at least one coincident resonance having a modal gain sufficient to generate corresponding ones of said at least one laser emission. 
   
     
     
         2 . The device of  claim 1 , wherein the rear facet reflectivity is fixed and the front facet reflectivity is chosen such that the modal gain of the first plurality of resonances is less than said lasing threshold. 
     
     
         3 . The device of  claim 1 , wherein the reflectivity of the front facet is fixed and the reflectivity of the volume Bragg grating is selected such that the modal gain at the substantially coincident resonance is greater than the lasing threshold. 
     
     
         4 . The device of  claim 1 , wherein the reflected portion of the light emission from the volume Bragg grating is less than 35% at said laser emission. 
     
     
         5 . The device of  claim 1 , wherein the reflectivity of the front facet is in the range from 0.1-10.0% at said at least one laser emission. 
     
     
         6 . The device of  claim 1 , wherein the reflectivity of the rear facet is selected such that the modal gain of the first plurality of resonances is less than a lasing threshold. 
     
     
         7 . The device of  claim 1 , wherein the rear facet has a reflectivity of at least 80% at the laser emission. 
     
     
         8 . The device of  claim 1 , wherein the rear facet is coated with a low reflectivity coating. 
     
     
         9 . The device of  claim 1 , wherein a length of the semiconductor gain section is selected based on said second reflectivity. 
     
     
         10 . The device of  claim 8 , wherein the length of the semiconductor gain section is in a range of 0.2-3.0 mm (millimeters). 
     
     
         11 . The device of  claim 1  further comprising:
 a discrete etalon element positioned between said front facet of said semiconductor gain section and said volume Bragg grating, wherein said etalon is tilted at an angle to the light emission, said etalon element comprising:
 a front optical surface; and 
 a rear optical surface, each of said front and rear optical surfaces coated with partially reflective coatings, said reflective coatings determining allowed resonances of the discrete etalon, wherein one of said allowed resonances is substantially coincident with said substantially coincident ones of said plurality of first resonances and said plurality of second resonances. 
 
 
     
     
         12 . The device of  claim 1 , wherein a wavelength of the laser emission is in a range of 375 nm and 3000 nm. 
     
     
         13 . The device of  claim 11 , wherein the front optical surface and rear optical surface of the discrete etalon are each coated to reflect between approximately 10% and 99% said laser emission. 
     
     
         14 . The device of  claim 1 , further comprising:
 an optics section collecting and collimating said light emission into said volume Bragg grating.   
     
     
         15 . A device configured to generate at least one laser emission, the device comprising:
 a semiconductor gain section configured to generate a light emission, said semiconductor gain section comprising:   a gain region having a known length;
 a rear facet having a first reflectivity; and 
 a front facet having a second reflectivity, said gain region, 
   rear facet and front facet forming a first resonant cavity having a first plurality of resonances; and   a volume Bragg grating, having a known reflectivity configured to:
 receive said light emission, and 
 reflect a portion of the received light emission back into the semiconductor gain section, wherein said volume Bragg grating and the rear facet of the semiconductor gain section form a second resonant cavity overlapping the first resonant cavity, said second resonant cavity generating a second plurality of resonances, wherein neither the first resonant cavity nor the second resonant cavity exhibit sufficient modal gain for either the first plurality of resonances or the second plurality of resonances to individually achieve a lasing threshold and wherein said at least one laser emission occurring at substantially coincident ones of said first plurality of resonances and said second plurality of resonances. 
   
     
     
         16 . The device of  claim 15 , wherein the reflectivity of the volume Brag grating is fixed and the length of the gain region are selected such that the modal gain at said substantially coincident resonances is greater than the lasing threshold. 
     
     
         17 . The device of  claim 15 , wherein the length of the gain region is fixed and a unit gain of the gain section is selected such that the modal gain at the substantially coincident resonances are greater than the lasing threshold. 
     
     
         18 . The device of  claim 15 , wherein said unit gain of the semiconductor gain section is increased by at least one of: increasing a modal confinement factor, increasing a number of quantum wells and employing quantum wells with one of tensile strain and compressive strain. 
     
     
         19 . The device of  claim 15 , wherein the length of the semiconductor gain section is in the range of 0.2-3.0 mm (millimeters). 
     
     
         20 . The device of  claim 15 , wherein said volume Bragg grating receives said light emission from said front facet of said gain section. 
     
     
         21 . The device of  claim 15 , wherein said volume Bragg grating receives said light emission from said rear facet of said gain section. 
     
     
         22 . The device of  claim 15 , further comprising:
 an optics section positioned between said gain section and said volume Bragg grating, said optics section configured to:
 receive said light emission; and 
 provide said light emission to said volume Bragg grating. 
   
     
     
         23 . The device of  claim 15 , further comprising:
 an etalon, positioned between said gain section and said volume Bragg grating, forming a cavity having a plurality of third resonances, at least one of said third resonances being substantially coincidence with said substantially coincident resonances.   
     
     
         24 . The device of  claim 15 , wherein said substantially coincident resonances are determined based on at least one of: a position of the VBG with respect to the gain section and a temperature of one of: the first resonant cavity and the second resonant cavity. 
     
     
         25 . The device of  claim 15 , wherein tuning a center wavelength of the reflected portion of the light emission from the volume Bragg grating by varying a temperature of the volume Bragg grating.