VCSEL with vertical offset operating region providing a lateral waveguide and current limiting and method of fabrication

A vertical cavity surface emitting laser having an operating wavelength at which light emission occurs, the laser comprising:

• first and second mirror stacks with an active region sandwiched therebetween, the active region including an active layer;
• a preferred operating region defined in the first and second mirror stacks and the active region with portions of the second mirror stack outside of the preferred operating region being removed, the preferred operating region defining therein a volume with a generally circular cross-section having a diameter approximately equal to a mode size for a lowest order of operating mode for the vertical cavity surface emitting laser;
• and
• the operating region being vertically offset from portions of the first and second mirror stack and the active region which are outside of the operating region approximately an odd multiple of a quarter wavelength of the operating frequency so that the preferred operating region in the first mirror stack and at least the active layer of the active region are surrounded with portions of the first mirror stack and the active region outside of the preferred operating region having a different index of refraction so as to define a lateral waveguide in the preferred operating region.

A method of manufacturing a vertical cavity surface emitting laser having an operating wavelength at which light emission occurs, the method comprising the steps of:

• providing a supporting substrate having a substantially planar surface;
• forming an offset in the substrate and substantially centrally located in the surface, the offset defining a surface lying in a first plane and an outer edge lying in a second plane parallel to the first plane and spaced therefrom with the first and second planes being parallel to the planar surface, the offset surface defining therein a generally circular area with a diameter approximately equal to a mode size for a lowest order of operating mode for the vertical cavity emitting laser, and the first and second planes being spaced apart approximately an odd multiple of a quarter wavelength of the operating frequency;
• positioning a first mirror stack on the surface of the substrate so as to overlie the offset in the substrate and a portion of the surface surrounding the offset;
• positioning an active region including at least a layer parallel and in overlying abutting engagement with the first mirror stack and substantially coextensive therewith;
• positioning a second mirror stack parallel and in overlying abutting engagement with the active region and substantially coextensive therewith;
• further positioning the first and second mirror stacks and the active region so that first portions of the active region and the first and second mirror stacks are offset from second surrounding portions of the active region and the first and second mirror stacks, respectively, by the offset in the substrate so as to define a lateral waveguide;
• and
• removing portions of the second mirror stack overlying the portions of the surface surrounding the offset in the substrate.

A method of manufacturing a vertical cavity surface emitting laser having an operating wavelength at which light emission occurs, the method comprising the steps of:

• providing a supporting substrate having a substantially planar surface;
• forming an offset in the substrate and substantially centrally located in the surface of the substrate, the offset in the substrate defining an offset surface lying in a first plane and an outer edge lying in a second plane parallel to the first plane and spaced therefrom with the first and second planes being parallel to the planar surface, the offset surface defining therein a generally circular area with a diameter approximately equal to a mode size for a lowest order of operating mode for the vertical cavity surface emitting laser, and the first and second planes being spaced apart approximately an odd multiple of a quarter wavelength of the operating frequency;
• positioning a first mirror stack on the surface of the substrate so as to overlie the offset in the substrate and a portion of the surface surrounding the offset;
• positioning an active region including at least a layer parallel and in overlying abutting engagement with the first mirror stack and substantially coextensive therewith;
• positioning a second mirror stack parallel and in overlying abutting engagement with the active region and substantially coextensive therewith;
• further positioning the first and second mirror stacks and the active region so that first portions of the active region and the first and second mirror stacks are offset from second surrounding portions of the active region and the first and second mirror stacks, respectively, by the offset in the surface of the substrate so as to define a lateral waveguide;
• and
• removing portions of the second mirror stack overlying the portions of the surface surrounding the offset in the substrate using the steps of forming a mask on the second mirror stack to define portions of the second mirror stack to be removed by depositing a layer including TiWNx on the second mirror stack and removing all of the layer except a portion overlying the offset in the substrate and plasma etching unmasked portions of the second mirror stack.

A method of manufacturing a vertical cavity surface emitting laser having an operating wavelength at which light emission occurs, the method comprising the steps of:

• providing a supporting substrate having a substantially planar surface;
• forming an offset in the substrate and substantially centrally located in the surface of the substrate, the offset in the substrate defining an offset surface lying in a first plane and an outer edge lying in a second plane parallel to the first plane and spaced therefrom with the first and second planes being parallel to the planar surface, the offset surface defining therein a generally circular area with a diameter approximately equal to a mode size for a lowest order of operating mode for the vertical cavity surface emitting laser, and the first and second planes being spaced apart approximately an odd multiple of a quarter wavelength of the operating frequency;
• positioning a first mirror stack on the surface of the substrate so as to overlie the offset in the substrate and a portion of the surface surrounding the offset;
• positioning an active region including at least a layer parallel and in overlying abutting engagement with the first mirror stack and substantially coextensive therewith;
• positioning a second mirror stack parallel and in overlying abutting engagement with the active region and substantially coextensive therewith;
• further positioning the first and second mirror stacks and the active region so that first portions of the active region and the first and second mirror stacks are offset from second surrounding portions of the active region and the first and second mirror stacks, respectively, by the offset in the surface of the substrate so as to define a lateral waveguide;
• removing portions of the second mirror stack overlying the portions of the surface surrounding the offset in the substrate using the steps of forming a mask on the second mirror stack to define portions of the second mirror stack to be removed by depositing a layer including TiWNx on the second mirror stack and removing all of the layer except a portion overlying the offset in the substrate;
• and
• forming a dielectric layer over all exposed portions of the second mirror stack.