Vertically integrated electro-absorption modulated lasers and methods of fabrication

A method of fabricating a monolithically integrated electro-absorption modulated laser (EML), wherein a distributed feedback (DFB) laser is vertically integrated with an electro-absorption modulator (EAM) and integrated electronic circuitry, comprising:

• providing a semi-insulating (SI) substrate;
• growing a blanket epitaxial layer structure on first and second areas of the SI substrate, the first area being designated for optical components of the EML and the second area being designated for electronic circuitry;
• the blanket epitaxial layer structure comprising:
• a first plurality of semiconductor layers for fabrication of electronic circuitry;
• at least one spacer layer comprising a selective etch stop;
• and
• a plurality of vertically stacked optical waveguides, wherein:
• a first level waveguide comprises layers structured as a passive output waveguide;
• a second level waveguide comprises layers structured as an EAM waveguide;
• a third level waveguide comprises layers structured as a DFB laser waveguide;
• protecting the first area and selectively removing from the second area the plurality of vertically stacked optical waveguides and the at least one spacer layer;
• processing the first plurality of semiconductor layers to define the electronic circuitry;
• protecting the second area comprising the electronic circuitry;
• processing the plurality of vertically stacked optical waveguides comprising:
• patterning layers of the third level waveguide to define a laser mesa comprising a DFB laser cavity having a surface etched grating (SEG), and a first laterally tapered vertical optical coupler extending from an optical output of the laser cavity;
• patterning layers of the second level waveguide to define a mesa of the EAM, and a second laterally tapered vertical optical coupler extending from an optical output of the EAM;
• patterning layers of the first level waveguide to define a passive output waveguide;
• the DFB laser cavity being laterally spaced from the EAM along the direction of optical propagation, and the first laterally tapered vertical optical coupler being structured to couple an emitted optical mode from the DFB laser cavity 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 passive output waveguide;
• providing first electrical connections between the electronic circuitry and the DFB laser for operating the DFB laser in CW mode and providing second electrical connections for driving the EAM.