Wavelength-tunable laser module using low-temperature cofired ceramic substrates

We realized a prototype series of the 1550-nm band wavelength-tunable laser module. The edge-emitting Fabry-Perot diode laser operates in the short external cavity configuration and is tuned by a silicon surface micromachined Fabry-Peacuterot interferometer device. Low-temperature cofired ceramic (LTCC) substrate technology was used in the module packaging to enable the passive alignment of the photonic components. Low conductor resistance and dielectric loss, multilayer structures with fine-line capability, compatibility with hermetic sealing, and the ability to integrate passive electrical components (resistors, capacitors, and inductors) into the substrate make LTCC a useful technology for telecommunication applications. In addition, the fair match of the thermal expansion coefficient to optoelectronic chips reduces packaging-induced thermomechanical stresses. The precision three-dimensional (3-D) structures, such as cavities, holes, and channels manufactured in the ceramic parts, ease the packaging process via the passive assembly. The wavelength tuning range of the realized modules ranged from 8 to 19 nm and single-mode fiber-coupled output power was between 100 and 570 muW. The hybrid arrangement uses standard laser chips and, therefore, potentially provides a cost-effective and easily configurable solution for last-mile fiber optic communications.