Transsub, an 850-nm VCSEL design grown as a bottom emitter with topside P and N contacts, emits in the direction of the substrate. Available from Ulm photonics GmbH, the VCSEL for direct flip chip has a mechanical robust surface on the emitting side, and contacts on the opposite allow easy assembly of single devices and arrays. On the wafer scale, a 100- to 300-µm-thick transparent glass substrate can replace the gallium arsenide. The design accommodates integrating lenses and fiber alignment marks by stacking additional wafers. Applications include very short reach interconnects and automotive datacom.