Why is mA important?

[usakicksass]

I read about mA ratings and a diode being left on at 100mA for all night, etc.. Can someone explain about mA and lasers.

 

[pullbangdead]

This is typically referring to the current being run through the diode. Generally, with the drivers everyone uses, the diode will take whatever voltage it needs as long as you control the current running through the diode. Every diode can handle a different amount of current, but most diodes in use out there have been explored and used enough that there are known "safe" ranges where diodes can be operated. For instance, Blu-ray diodes are known to be typically be ok running at 38 mA of current through the diode for continuous usage. Different red diodes can be run at different amounts of current, depending on the diode and its application: long open-can diodes are routinely run at 420 mA of current when well-heatsinked, and even higher if actively cooled. Senkat's diodes are not quite as robust, so they are typically run at slightly lower currents for continuous usage with no active cooling.

Generally speaking, the more current run through a diode, the more photons will be emitted from a diode. There are diminishing returns, where adding extra current at low currents can increase output a lot, put the same increase at higher currents will not increase light output nearly as much. And, diodes can only take so much current. Not all current gets used to output light, as nothing is completely efficient, so the rest of the input energy goes into heat in the diode. This heat can and will mess up the diode. One common way for the diode to fail is for the cavity mirrors to fail, known as COD, or catastrophic optical damage. This is what turns a laser diode into simply an LED, as it can't lase without mirrors.

 

[usakicksass]

I asked for a snack and got the full meal deal, thanks.

 

[jayrob]

Very well written pull! You could write a book man...
Jay

 

[nikokapo]

I asked for a snack and got the full meal deal, thanks.

thats what you always get with pullbang.

pullbangdead customer support ftw.

 

[pullbangdead]

I asked for a snack and got the full meal deal, thanks.

I aim to please.

Very well written pull! You could write a book man...
Jay

Gee, funny you should mention that...Starting my work towards my Ph.D on June 2nd, so I suppose in about 4 or 5 years I will have written a book of sorts on laser diodes...I guess it depends how long that dissertation ends up.

It's really weird though, my technical papers and lab reports are always some of the shortest in the class, while my forum posts are always some of the longest.

And that "complete guide to laser diodes and how they work" that I mentioned in a thread a while ago for the forum will be forth-coming, but between now and June 2nd I have to finish all my school work here to graduate and move across the country to where I'm starting grad school (North Carolina to California). But thank for the kudos, good to know I'm helping out, that's what we're here for.

 

[Murudai]

It's really weird though, my technical papers and lab reports are always some of the shortest in the class, while my forum posts are always some of the longest.

Heh, I know what you mean (I'm too new to lasers to do long posts here, but on other forums I sometimes write pages on random things, lol).

It's worse when I'm writing a lab report at the same time as I'm on forums, and I sit there and write an essay on the forums and put down a few scant sentences in the report, lol