Am I calculating this right?

[jcswimmer305]

If my green laser from radioshack has a module that can take about 200mA of current (driver and all...assuming the typical green module does this much) and I give it two 1.5V batteries, can it reach a max of 600mW, if modified?

I honestly thought this was bizarre, so that's why I'd like someone else to check this out for me. I think resistance plays a role in this, which is why the laser is powered down to 5mW (correct me if I'm wrong).

But if that last statement is true...then how much current is REALLY going through the diode from the driver? Would it be 1.6mA (calculating Amps = Watt/Volts)?

 

[Wolfman29]

No no no no no

So first, you have losses from the driver - for those drivers, you are looking at a maximum efficiency of 80% or so. Then you have the losses of electrical power to optical power (from the driver to the 808nm diode), which is usually, at most, 50% efficient. Then you have the losses from the conversion crystals by converting the 808nm input into 532nm green light output, which is, at most, usually 30% or so.

So, the *ideal* efficiency of the system is 12%, which is considering the best parts, etc. Now, we have 3V and 260mA input, which translates to 600mW input power. With 12% efficiency, we are looking 72mW output power, AT most. Now, it's probably a switching supply (depending on how good the driver is), so you are probably getting 72mW megahertz pulses, resulting in an output power of less than 5mW, with 72mW being the "peak power" for roughly 7% of each cycle.

 

[Benm]

There are plenty of losses indeed. It would typically take 600-700 mA diode current to reach 200 mW output power, on a good module. This would equate to the above figure of roughly 12% efficiency from pump diode electrical power to light output.

 

[Cyparagon]

Lasers are not 100% efficient. You lose ~33% in the driver, ~33% in the pump diode, and ~33% in the crystals.

 

[jcswimmer305]

Thanks everyone! Now are other lasers about this much efficient also? I'd assume they'd be a little higher since reds and blues don't have to pass through the 808nm. Does anyone know the actual efficiency of it though? (Percentage-wise I mean)

 

[Wolfman29]

Actually, IR diodes are the most efficient laser diodes out there.

As far as I can tell, 445nm diodes and LPC-815s all range from around 20-25% efficiency.