An optical transmitter device is disclosed. The optical transmitter device includes an optical integrating device, a carrier, and a thermo-electric cooler (TEC). The carrier has a top surface and a back surface opposite to the top surface. The carrier includes an insulating slab and a metal plate attached to the insulating slab. The metal plate has thermal conductivity better than thermal conductivity of the insulating slab. The insulating slab forms the top surface of the carrier that provides an interconnection thereon. The back surface mounts the optical integrating device thereon. The TEC faces the carrier and mounts the carrier thereon. The carrier has a base overlapped with the TEC and an extension not overlapped with the TEC, the extension mounting the optical integrating device thereon.