Heterogeneously integrated photonic platform with improved thermal performance

A method for making a device;

• the method comprising:
• forming a first element, comprising a dielectric material, on a substrate;
• defining a waveguide, configured to support a first optical mode, in the first element;
• forming a second element, comprising a thermal heatsink, on the substrate;
• planarizing a top surface comprising a top surface of the first element;
• attaching a third element comprising an active material to the planarized top surface;
• defining a waveguide configured to support a second optical mode in the third element where its position relative to the first element is defined by lithographic alignment marks;
• forming first electrical contacts in the third element;
• and
• forming, on the planarized top surface, a fourth element between and in contact with the first and third elements, the position of the fourth element relative to the first and third element being defined by lithographic alignment marks;
• and
• defining an intermediate waveguide in the fourth element, the intermediate waveguide element being configured to facilitate transformation between the first and second optical modes;
• and
• forming second electrical contacts in the third element and providing thermal coupling between the second and third elements.