[Laser] laser ratings

[James Whitfield]

Recent discussions about laser power have revealed a gap in my understanding of such things.

I have a laser pointer that I have been using for several years for demos and as the emitter element on an MCW transmitter.  The label says its maximum power output is 4 mWatt.  It is built for two AA batteries.  I measured the input voltage.  It seems noticeably weak at 2.5 volts and it draws 16 mA.  With fresher batteries, it seems full power using 2.8 volts drawing 33 mA.

With my MCW transmitter, I pulse it with about 30 mA at about 400 Hz, not bothering to try to control the voltage, just a hard current limit, pulsed or not.

The numbers say its input power is 40 mWatt for the weak condition, and over 90 for the bright.  I am pretty sure that most of that power is actually going into the laser diode.  If the rating is output power, then the conversion efficiency seems to be less than 10%.  I suppose that is on par with an underdriven tube type class A amplifier.

Anyway, I was wondering if someone can explain the laser power rating system, or maybe provide a link where that information is available.

Thanks in advance.


James
 n5gui