Thermal management is critical when testing vertical cavity surface emitting lasers (VCSELs) at the semiconductor wafer, bar, and chip-on-carrier production stages. As a result, pulsed testing is commonly used to minimize power dissipation. However, several sources of error remain when pulse testing VCSELs or laser diodes, including problems with coupling high current pulses to the DUT, optical detector coupling, and both slow response and inaccuracy in the detector itself. This paper explores solutions to each of these problems that can deliver shorter test times, more accurate results, and lower reject rates.
Tektronix (Keithley), April 2020