Light-current-voltage (LIV) testing for vertical-cavity surface-emitting laser (VCSEL) devices requires precise control of the injection current (I) and light output power (L) measurement. The test process involves systematically varying the current, measuring the corresponding light output, and recording the voltage (V) applied. Test engineers can use the source / measure units (SMUs) to provide programmable current sourcing to apply a wide range of currents to the VCSEL. They also need high-speed photodetectors to capture the emitted light, measuring its power precisely. Engineers can plot these data points to create the LIV curve, which provides a detailed understanding of the VCSEL's performance characteristics under different operating conditions.
The key challenge lies in conducting tests that mitigate the impact of self-heating on the diode and ensure accurate measurement results. Temperature variations significantly influence the behavior of laser diodes. As the temperature rises, laser efficiency tends to decrease. Test engineers require a narrower pulsed output capability to suppress the self-heating effect and a high-speed sampling rate to capture the fast and extremely narrow current / voltage pulses to validate the dynamic characteristics. It is also necessary to synchronously measure the photodetector (PD) current during the pulsed light emission from the laser diode (LD). This requires precise timing control between the LD and PD within the measurement software and SMU.
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Additional resources for narrow-pulsed LIV testing
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