POLARIZATION CONTROL IN VERTICAL CAVITY SURFACE EMITTING LASERS USING OFF-AXIS EPITAXY
A polarization pinned long wavelength vertical cavity surface emitting laser (VCSEL). The VCSEL includes a III V semiconductor substrate. A bottom DBR mirror is formed on the semiconductor substrate. An active region is formed in an off-axis orientation on the bottom DBR mirror. The active region includes a surfactant that suppresses unwanted three dimensional growth. A top DBR mirror formed on the active region.
1 . A method of fabricating a long wavelength VCSEL, the method comprising:
forming an off-axis orientation bottom DBR mirror on an off-axis orientation III V semiconductor substrate;
forming an active region on the off-axis orientation bottom DBR mirror, wherein forming an active region comprises forming the active region in an off-axis orientation using a surfactant to inhibit unwanted three dimensional growth; and
forming a top DBR mirror on the active region.
2 . The method of claim 1 , wherein the III V semiconductor substrate is GaAs.
3 . The method of claim 1 , wherein the surfactant is Antimony.
4 . The method of claim 1 , wherein forming an active region includes using about 1% Antimony and 2% Nitrogen.
5 . The method of claim 1 , wherein the acts recited are performed at a pressure of about 8×10 −8 torr SB beam equivalent pressure.
6 . The method of claim 1 , wherein forming an active region in an off-axis orientation comprises forming the active region in a 111 A or 111 B direction.
7 . The method of claim 1 , wherein forming an active region in an off-axis orientation comprises forming the active region in a 311 orientation.
8 . The method of claim 1 , wherein forming an active region in an off-axis orientation comprises forming the active region in a minimal off-axis orientation.
9 . The method of claim 1 , further comprising forming a layout asymmetry that includes a thermal asymmetry formed by a metal deposition pattern.
10 . The method of claim 1 , further comprising forming a layout asymmetry that includes a mechanical asymmetry formed by a trench pattern.
11 . The method of claim 1 , further comprising forming a layout asymmetry that includes an electrical asymmetry caused by a current injection method.
12 . The method of claim 1 , further comprising forming an an assembly by optically coupling a ¼ waveplate to the VCSEL.
13 . The method of claim 1 , wherein forming an active region comprises forming the active region in an off-axis orientation using migration enhanced epitaxy.
14 . The method of claim 1 , wherein forming an active region comprises using appropriate growth conditions to create sufficient step heights and densities to pin polarization.
15 . A long wavelength VCSEL comprising:
an off-axis orientation III V semiconductor substrate;
a bottom off-axis orientation DBR mirror formed on the off-axis orientation semiconductor substrate;
an active region formed in an off-axis orientation on the bottom DBR mirror, the active region comprising a surfactant that suppresses unwanted three dimensional growth; and
a top DBR mirror formed on the active region.
16 . The VCSEL of claim 15 wherein the III V semiconductor substrate is GaAs.
17 . The VCSEL of claim 15 , wherein the surfactant is Antimony.
18 . The VCSEL of claim 15 , the active region includes about 1% Antimony and 2% Nitrogen.
19 . The VCSEL of claim 15 , wherein the active region is in an off-axis orientation in a 111 A or 111 B direction.
20 . The VCSEL of claim 15 , wherein the active region in an off-axis orientation in a 311 orientation.
21 . The VCSEL of claim 15 , further comprising a thermal asymmetry formed by a metal deposition pattern.
22 . The VCSEL of claim 15 , further comprising a mechanical asymmetry formed by a trench pattern.
23 . The VCSEL of claim 15 , further comprising an electrical asymmetry caused by a current injection method.
24 . An optical assembly comprising:
a long wavelength VCSEL, wherein the VCSEL is fabricated in an off-axis orientation to pin polarization of the VCSEL, wherein the VCSEL comprises an active region, the active region comprising a surfactant to inhibit unwanted three dimensional growth cause by seeds in the active region that exist when the active region is formed in the off-axis orientation; and
a λ/4 waveplate optically coupled to the VCSEL and configured to cause light reflected back into the VCSEL to be orthogonal to the pinned polarization of the VCSEL.