What is the rating on a laser diode?

Searching both this forum and google somehow didn't result in an answer.

If I have a 300mw laser diode what does that mean? It can handle 300mw of power? The data sheet says it has a 2.2V operating voltage and a max operating current of 400mA thats 880mw! So what does this rating represent?

kaminsknator said:

Searching both this forum and google somehow didn't result in an answer.

If I have a 300mw laser diode what does that mean? It can handle 300mw of power? The data sheet says it has a 2.2V operating voltage and a max operating current of 400mA thats 880mw! So what does this rating represent?

Click to expand...

That's how much power the laser outputs. A veteran can give you a much better description if needs be.

Have fun :beer:

It's called "efficiency" while it would be nice if 100% of the input power made it to the output power, that doesn't happen in the real world.

In this case, 300mW / 800mW x 100 = 37.5% of the input energy goes to the light output.


Bob Diaz

It wouldn't be 880mw. The efficency of things in real world will never be 100%. Just like a transformer, you can never get a 100% efficiency transformer. For this, the efficency is around 37.5% although it would vary depending on the type of lense you use.
Edit: I would recommend you to use a 808nm diode to built a laser. They are almost invisible to human eyes and it might give you a false sense of safety.

Input would be 2.2V * 0.4A = 0.88W as you said with a 300mW Optical output

Diodes are rated for optical output power .

It doesnt seem like you have gotten a straight answer yet... when it says "1w" as a rating (though unlikely) it means it outputs 1w of power, look up some videos of different powers and wavelengths to get an idea. Ive at least never seen the input listed in watts...

Anyone interested in the details of power ratings on lasers this articles does a decent job: http://www.coherent.com/downloads/aboutmeasuringlaserpowerndenergyoutputfinal.pdf

The exert that answered my question:
The power of a laser is measured in Watts (and often reported in terms of nW, mW, W, etc.). This is referring to the optical power output of the laser beam, which is the continuous power output of continuous wave (CW) lasers, or the average power of a pulsed or modulated laser.The energy of a laser typically refers to the output of a pulsed laser and is related to the power output, where the energy (E) is the laser’s peak power (PPEAK) multiplied by the laser pulse duration (t).

So as stated in an earlier comment the rating refers to the produced optical power while it's efficiency requires much more power to achieve those results.

300mW refers to the optical output power. it is not 100% efficient, so it takes 880mW of electricity, converts some to light (300mW) and the rest to heat and back into the circuit.