Electrical – How to calculate a laser diodes amps from its wavelength


I am building a laser driver circuit.

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Every laser diode requires a different amount amps to run correctly without burning. So instead of me coming on here and asking what each laser diodes amps are, is there an equation that maybe takes the nm wavelength and the output power into hand and allows you to figure out the amps required to power it? In this circuit I use V = IR where V = 1.25 and r has to be calculated. the resistor are in series so 2×10 Ohm lasers are 5 Ohms output. 1.25/5 = 0.25A or 250mA. But that is for this red laser diode. So how do i calculate the amps needed for all different laser diodes?

Also how do i calculate what capacitance i will need based off the laser diode?

Best Answer

There is no one-to-one relationship between laser diode wavelength and maximum operating current.

The maximum operating current typically depends mainly on the physical size of the diode, and what kind of heat sink it is attached to, as these things determine how much power it can dissipate without burning up.

In some cases, it could depend on details of the cavity structure, or the type of (anti-)reflective coating on the facets, as these can affect failure modes that can occur when substantial optical power is localized in the laser cavity.

The device's structure (the geometry of the layers of semiconductor that form the diode) will both determine the wavelength and determine the power efficiency of the device (which will affect the maximum operating power), but there are many ways to make a laser of any given wavelength, so this doesn't cause a direct correlation between wavelength and power.

So the best way to find out the maximum operating current for any given laser is to consult the datasheet provided by the manufacturer.