Substrate exchanged VCSEL offers ability to integrate

6 June 2003 Ulm, Germany, Lightwave--VCSEL vendor ULM-photonics/Germany is sampling its new 850-nm "TRANSSUB VCSEL" at 3.125 Gbits/sec. This GaAs VCSEL design has been grown as a bottom emitter with topside P and N contacts; it therefore emits in the diretion of the substrate. On wafer scale a 100- to 300-micron thick transparent glass substrate can replace the GaAs.

The technology offers a VCSEL for direct flip chip bonding with a mechanical robust surface on the emitting side and contacts on the opposite side similar to an SMD device. The design enables easy assembly of single devices and arrays. It also accommodates integration of lenses and fiber alignment marks by stacking additional wafers. Fibers or connectors may touch the glass surface of the VCSEL without influencing the performance and lifetime.

The design is in step with the need to reduce the packaging costs of lasers. Two years ago the cost ratio of VCSEL chip to package was in the range of 1:1; today it approachinges 1:4, ac-cording to ULM-photonics. To company believes that to reduce overall cost, there is need for functional integration of the emitter, coupling, and fiber alignment. The TRANSSUB VCSEL enables the integration of these functions at wafer scale, allowing a full testable optical subassembly. Targeted applications are low-cost approaches in the very short reach interconnects as well as automotive datacom.