We all know that laser diodes are widely used in daily life. Many people will ask how to solve the unstable power of laser diodes. Let's take a look at it together.

The output power of laser diode is unstable, 99% of which is caused by the problems of driving/temperature control/reflection (or coupling). The problems can be basically solved by checking in sequence and adding monitoring loop/protection.

Use power meter and oscilloscope to observe the output waveform and noise, and visually/range to see if the average power has obvious drift; Oscilloscope to see if there is high-frequency jitter, pulse or periodic fluctuation. Check the driving power supply (constant current source) and grounding, whether the constant current source is stable, and whether the output has ripple or transient. Whether there is virtual welding on cables, connectors and solder joints, and whether the grounding is good.

Check the temperature control (TEC) and thermal path, and whether the TEC current is in the working area; Whether the heat sink/hot glue/thermal paste is aged or badly extruded. See if there is any optical feedback or coupling problem (especially fiber core or optical cavity). The reflected light will lead to mode jump or power oscillation. Whether the optical fiber interface, collimating lens and optical isolator are installed correctly. Checking the aging of laser body (facet damage, aging, mode jump) will increase the threshold current, decrease the efficiency and become unstable. Check the environment (vibration, electromagnetic interference, air flow), vibration will affect the coupling; Strong winds or the rhythm of cooling fans can cause temperature cycling.

The method introduced above is how to solve the problem when the output power of laser diode is unstable. I hope it will be helpful to you.