wafer embodiments of the present invention provide a highly efficient and reliable method for burning in semiconductor devices on wafer before the wafer is cut into individual dies using the technique of thermal rollover this technique essentially involves driving the device with a current that is much higher that its maximum operating current and at an elevated ambient temperature under these conditions the internal temperature of the device being treated rises significantly above the normal operating temperature when a certain threshold is reached the elevated driving current and temperature will cause a typical vcsel device to stop lasing i e output power falls off dramatically however this is not a catastrophic effect that will induce permanent damage to the device it is simply because the significant increase of the internal temperature of the vcsel device junction temperature due to the current increase causes the cavity resonance peak to move out of the range of optical gain in the device so the optical gain for light amplification diminishes gradually as the device junction temperature increases beyond a certain limit in other words optical power output from the device will not increase with the current as it normally does when the current reaches a certain limit once the threshold.