Vertically integrated electro-absorption modulated lasers and methods of fabrication

A monolithically integrated electro-absorption modulated laser (EML) comprising:

• a semi-insulating (SD) substrate;
• an epitaxial layer stack formed on the SI substrate;
• the epitaxial layer stack defining a plurality of vertically stacked waveguides, wherein the epitaxial layer stack comprises;
• a first plurality of semiconductor layers formed on the SI substrate, the first plurality of semiconductor layers providing a first optical waveguide comprising an output waveguide;
• a second plurality of semiconductor layers disposed above the first plurality of semiconductor lavers, the second plurality of semiconductor layers providing a second optical waveguide comprising an electro-absorption modulator (EAM) waveguide;
• a third plurality of semiconductor layers disposed above the second plurality of semiconductor lavers, the third plurality of semiconductor layers providing a third optical waveguide comprising a laser waveguide;
• the third optical waveguide is structured to define a distributed feedback (DFB) laser comprising a laser cavity and a first laterally tapered vertical optical coupler extending from an optical output of the laser cavity;
• the second optical waveguide is structured to define a mesa of the EAM and a second laterally tapered vertical optical coupler extending from an optical output of the EAM;
• the laser cavity is spaced from the EAM along a direction of optical propagation, the first laterally tapered vertical optical coupler being structured to couple an emitted optical mode from the laser an input of the EAM;
• and
• the second laterally tapered vertical optical coupler is structured to vertically couple a modulated output from the EAM to the output waveguide;
• and
• the DFB laser having first electrical contacts for operating the DFB laser in CW mode;
• and
• the EAM having second electrical contacts for driving the BAM, and wherein,
• the epitaxial layer stack comprises an other plurality of semiconductor layers comprising heterojunction bipolar transistors (HBTs) of electronic circuitry underlying the plurality of vertically stacked optical waveguides, said other plurality semiconductor layers of the electronic circuitry being vertically separated from the plurality of vertically stacked optical waveguides by at least one spacer layer;
• the electronic circuitry comprising a laser driver and EAM driver and control circuitry;
• and
• interconnect metallization providing electrically conductive interconnect tracks between the laser driver and the first electrical contacts of the laser and between EAM driver and control circuitry and the second electrical contacts of the EAM.

A monolithically integrated electro-absorption modulated laser (EML) comprising:

• a semi-insulating (SI) substrate;
• an epitaxial layer stack formed on the SI substrate;
• the epitaxial layer stack defining layers comprising electronic circuitry and a plurality of vertically stacked optical waveguides, wherein the epitaxial layer stack comprises:
• a first plurality of semiconductor layers of the electronic circuitry formed on the SI substrate comprising heterojunction bipolar transistors;
• a second plurality of semiconductor layers disposed above the first plurality of semiconductor layers, the second plurality of semiconductor layers providing a first optical waveguide comprising an output waveguide;
• a third plurality of semiconductor layers disposed above the second plurality of semiconductor layers, the third plurality of semiconductor layers providing a second optical waveguide comprising an electro-absorption modulator (EAM) waveguide;
• a fourth plurality of semiconductor layers disposed above the third plurality of semiconductor layers, the fourth plurality of semiconductor layers providing a third optical waveguide comprising a laser waveguide;
• the third optical waveguide is structured to define a distributed feedback (DFB) laser comprising a laser cavity and a first laterally tapered vertical optical coupler extending from an optical output of the laser cavity;
• the second optical waveguide is structured to define the EAM and a second laterally tapered vertical optical coupler extending from an optical output of the EAM;
• the laser cavity is spaced from the EAM along a direction of optical propagation, the first laterally tapered vertical optical coupler being structured to couple an emitted optical mode from the laser to an input of the EAM;
• and
• the second laterally tapered vertical optical coupler being structured to vertically couple modulated output from the EAM to the output waveguide;
• and
• the electronic circuitry comprising a laser driver and EAM driver and control circuitry;
• and
• first electrical connections comprising conductive tracks between the laser driver and the DFB laser, and second electric connections comprising conductive tracks between the EAM driver and control circuitry and the EAM.