A quick quiz about ESD and laser diodes

Question 1: Here we have a 10 cm piece of copper braid that is shorting the terminals of the laser diode. Is this laser diode safe from ESD?…


…NO! This laser diode would be destroyed by ESD (and we’ve done experiments to prove it). As noted in the ESD Protection Requirements section of our Human Body Model-related web page, in order for the laser diode to be safe from ESD, the protection means must offer an impedance less than 50 milliohms over a frequency range of 20MHz to 1GHz! Due to the “long” length of this shorting wire, the resulting inductance offers an impedance greater than 50 milliohms at 1GHz.



Question 2: Here we have reduced the length of the copper braid to 5 cm. Is this laser diode safe from ESD?…


…MAYBE… At 5 cm (round trip) there is a 50-50 chance that this laser diode would be destroyed by ESD (again, we’ve done the experiments to prove it). Basically, the inductance at 1GHz is still a bit too high to offer complete protection.

These two experiments offer an important lesson. They demonstrates that, in order to be effective, the ESD protection means must be closer than 5cm (round trip) to the laser. From a practical standpoint, this this means two leads with 2.5cm length. Ideally, the ESD protection means should be placed as close as possible to the laser diode.



Question 3: OK, this picture shows the ESD protection right at the laser diode. Is the laser diode in this picture safe?…


…NO! This is a trick question. The laser in this picture does not use LASORB so it is not safe. (The manufacturer used a resistor and capacitor, but as described here and here, this does not provide sufficient ESD protection. The manufacturer had the right instinct, but used the wrong part…)



Question 4: Now, in this picture, the ESD protection means is placed in the power supply. Is the diode still protected?…


…NO! As discussed above, the distance is far too great to prevent ESD damage.



A final question: Are your laser diodes protected by LASORB? It is the only ESD protection device specifically designed to protect laser diodes. This website has additional information about how LASORB outperforms all other methods of diode protection.