DBR laser with improved thermal tuning efficiency
View Patent ↗A distributed Bragg reflector (DBR) includes a base substrate and a gain medium formed on the base substrate. A waveguide positioned above the base substrate in optical communication with the gain medium and defines a gap extending between the base substrate and the waveguide along a substantial portion of the length thereof. The waveguide may have a grating formed therein. A heating element is in thermal contact with the waveguide and electrically coupled to a controller configured to adjust optical properties of the waveguide by controlling power supplied to the heating element.
1. A method for forming an optical device comprising:
forming a first layer formed of a first material;
forming a second layer formed of a second material different from the first material;
selectively etching the second layer to form at least one discrete area;
forming one or more additional layers of at least a third material different from the second material;
forming a waveguide in the at least one additional layers;
removing a portion of the at least one additional layers adjacent the waveguide such that at least one surface of the at least one discrete area is exposed;
forming a support layer extending across the at least one surface of the at least one discrete area;
forming an opening in the support layer such that a portion of the at least one surface is exposed;
exposing the at least one discrete area through the opening in the support layer to an etchant that removes the second material faster than the first and third materials; and
wherein the first and third materials include InP and wherein the second material includes InGaAs or InGaAsP.
2. The method of claim 1 , further comprising forming a grating in the waveguide, the at least one discrete area being coextensive with at least a portion of the grating.
3. The method of claim 1 , wherein the first and third materials are InP and the second material is InGaAsP, the method further comprising, prior to performing the step of removing a portion of the at least one additional layers adjacent the waveguide:
forming a contact layer comprising InGaAsP over the at least one additional layers;
forming a first SiO 2 layer over the InGaAsP layer;
etching away at least one edge of the contact layer; and
growing a second SiO 2 layer having a portion extending entirely across the at least one edge of the InGaAsP layer.
4. The method of claim 1 , comprising creating an air gap between a raised substrate and a base substrate.
5. The method of claim 1 , comprising:
forming the first layer as a substrate with n-InP as the first material;
forming the second layer on the first layer with InGaAsP as the second material;
forming a first n-InP layer on the second layer;
forming at least one additional layer of n-InP as the third material on the at least one discrete area that was selectively etched; and
forming the waveguide on the at least one additional layer of n-InP, wherein the waveguide includes at least one multi-quantum well (MQW) portion and at least one distributed Bragg reflector (DBR) portion coupled together with at least one butt joint.
6. The method of claim 5 , comprising:
forming Fe—InP blocking portions along the at least one MWQ portion and at least one DBR portion;
removing a portion of the Fe—InP blocking portions and the at least one additional layer of n-InP adjacent the DBR portion by selectively etching on both sides of the such that the at least a portion of each of the at least two discrete areas is exposed; and
exposing, by wet etching, the at least two discrete areas to a wet etchant that removes the InGaAsP of the second layer faster than the n-InP of the first and third layers such that portions of the third layer of n-InP become pillars.
7. The method of claim 5 comprising forming a multi-quantum well (MQW) layer on the additional layer of n-InP.
8. The method of claim 7 , comprising optionally forming a second n-InP layer on the multi-quantum well (MQW) layer.
9. The method of claim 6 , wherein the pillars include InGaAsP and InP.
10. The method of claim 6 , wherein the pillars include InP and are substantially devoid of InGaAsP.
11. The method of claim 6 , wherein the removed InGaAsP become air gaps.
12. A method for forming an optical device comprising:
forming a first layer formed of a first material;
forming a second layer formed of a second material different from the first material;
selectively etching the second layer to form at least one discrete area;
forming one or more additional layers of at least a third material different from the second material;
forming a waveguide in the at least one additional layers;
forming a grating in the waveguide, the at least one discrete area being coextensive with at least a portion of the grating;
removing a portion of the at least one additional layers adjacent the waveguide such that at least one surface of the at least one discrete area is exposed;
forming a support layer extending across the at least one surface of the at least one discrete area;
forming an opening in the support layer such that a portion of the at least one surface is exposed;
exposing the at least one discrete area through the opening in the support layer to an etchant that removes the second material faster than the first and third materials; and
wherein the first and third materials include InP and wherein the second material includes InGaAs or InGaAsP.
13. The method of claim 12 , wherein the first and third materials are InP and the second material is InGaAsP, the method further comprising, prior to performing the step of removing a portion of the at least one additional layers adjacent the waveguide:
forming a contact layer comprising InGaAsP over the at least one additional layers;
forming a first SiO 2 layer over the InGaAsP layer;
etching away at least one edge of the contact layer; and
growing a second SiO 2 layer having a portion extending entirely across the at least one edge of the InGaAsP layer.
14. The method of claim 12 , comprising creating an air gap between a raised substrate and a base substrate.
15. The method of claim 12 , comprising:
forming the first layer as a substrate with n-InP as the first material;
forming the second layer on the first layer with InGaAsP as the second material;
forming a first n-InP layer on the second layer;
forming at least one additional layer of n-InP as the third material on the at least one discrete area that was selectively etched; and
forming the waveguide on the at least one additional layer of n-InP, wherein the waveguide includes at least one multi-quantum well (MQW) portion and at least one distributed Bragg reflector (DBR) portion coupled together with at least one butt joint.
16. The method of claim 15 , comprising:
forming Fe—InP blocking portions along the at least one MWQ portion and at least one DBR portion;
removing a portion of the Fe—InP blocking portions and the at least one additional layer of n-InP adjacent the DBR portion by selectively etching on both sides of the such that the at least a portion of each of the at least two discrete areas is exposed; and
exposing, by wet etching, the at least two discrete areas to a wet etchant that removes the InGaAsP of the second layer faster than the n-InP of the first and third layers such that portions of the third layer of n-InP become pillars.
17. The method of claim 15 , wherein the pillars include InGaAsP and InP and the removed InGaAsP become air gaps.
18. The method of claim 15 , wherein the pillars include InP and are substantially devoid of InGaAsP.
19. The method of claim 12 , comprising configuring the grating for use as a distributed Bragg reflector.