Substrate structure for photonic assemblies and the like having a low-thermal-conductivity dielectric layer on a high-thermal-conductivity substrate body

Abstract

A substrate structure useful for photonics modules comprises a high-thermal-conductivity (e.g., greater than 20 W/m°K) substrate body with a low-thermal-conductivity (e.g., less than 5 W/m°K) dielectric layer overlying at least a portion of the substrate body. Patterned metal layers for electrical circuit connections can be located on the dielectric layer, on the substrate body (under the dielectric layer, on regions of exposed substrate body, or both), or on both. Where the laser is driven at high frequencies (e.g., 2.5 Gbits/sec), the dielectric layer material and thickness can be chosen to provide desired RF behavior. For example, the electrodes and dielectric layer can be configured to provide a transmission line with the desired impedance. Further, where it is desired to solder a component to the substrate, a heater resistor can be formed on the dielectric layer, thereby facilitating soldering the component.