Diode Laser Power Supplies

This includes immunity to power line transients as well as those that may occur during power-on and power-off cycling. The parameters of many electronic components like ICs are rarely specified during periods of changing input power. Special laser diode drive chips are available which meet these requirements but a common
Diode Laser Power Supplies - schematic

op-amp may not be suitable without extreme care in circuit design - if at all. Current regulation. Efficiency and optical power output of a laser diode goes up with decreasing temperature. This means that without optical feedback, a laser diode switched on and adjusted at room temperature will have reduced output once it warms up. Conversely, if the current is set up after the laser diode has warmed up, it will likely blow out the next time it is switched on at room temperature if there is no optical feedback based regulation. Note that the damage from improper drive is not only due to thermal effects (though overheating is also possible) but due to exceeding the maximum optical power density (E/M field gradients ) at one of the end facets (mirrors) - and thus the nearly instantaneous nature of the risk. The optical output of a laser diode also declines as it heats up. This is reversible as long as no actual thermal damage has taken place. However, facet damage due to exceeding the optical output specifications is permanent. The result may be an expensive LED or (possibly greatly) reduced laser emission. I accidentally blew one visible laser diode by neglecting to monitor the current but it wasn`t the sudden effect some people describe - the current really had to be cranked up well beyond the point where the brightness of the laser beam stopped increasing. It did indeed turn into a poor excuse for an LED. One data point...

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