A testing device may include a stage associated with holding an emitter wafer during testing of an emitter. The stage may be arranged such that light emitted by the emitter passes through the stage. The testing device may include a heat sink arranged such that the light emitted by the emitter during the testing is emitted in a direction away from the heat sink, and such that a first surface of the heat sink is near a surface of the emitter wafer during the testing but does not contact the surface of the emitter wafer. The testing device may include a probe card, associated with performing the testing of the emitter, that is arranged over a second surface of the heat sink such that, during the testing of the emitter, a probe of the probe card contacts a probe pad for the emitter through an opening in the heat sink.