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Semiconductor lasers

Started by Aleksandar Kuktin August 29, 2015
I tore up a computer mouse to get my grubby little paws on a laser.

Only.. I'm not sure it's a laser. Apart from testing the output for 
coherence, is there a way to tell a laser diode from a light-emitting 
diode?

Other than that, how do you drive these things? Is there some Internet-
accessible resource where this is explained? Usually, I begin my crawl 
with Wikipedia, but on the subject of driving lasers, Wikipedia is 
surprisingly silent. I'm about to start a search for the datasheet of the 
IC that was in the mouse I tore up, but I fear it might come up empty..
On Sat, 29 Aug 2015 21:52:50 +0000 (UTC), Aleksandar Kuktin
<akuktin@gmail.com> wrote:

>I tore up a computer mouse to get my grubby little paws on a laser. > >Only.. I'm not sure it's a laser. Apart from testing the output for >coherence, is there a way to tell a laser diode from a light-emitting >diode?
Illuminate a piece of white paper, in the dark. Lasers will show speckles. And lasers usually have very low beam divergence.
> >Other than that, how do you drive these things? Is there some Internet- >accessible resource where this is explained? Usually, I begin my crawl >with Wikipedia, but on the subject of driving lasers, Wikipedia is >surprisingly silent. I'm about to start a search for the datasheet of the >IC that was in the mouse I tore up, but I fear it might come up empty..
Most diode lasers can be driven like an LED, constant-current, or a voltage and a current-limiting resistor.
On Saturday, August 29, 2015 at 3:07:33 PM UTC-7, John Larkin wrote:
> On Sat, 29 Aug 2015 21:52:50 +0000 (UTC), Aleksandar Kuktin > <akuktin@gmail.com> wrote: > > >I tore up a computer mouse to get my grubby little paws on a laser. > > > >Only.. I'm not sure it's a laser. Apart from testing the output for > >coherence, is there a way to tell a laser diode from a light-emitting > >diode? > > Illuminate a piece of white paper, in the dark. Lasers will show > speckles. And lasers usually have very low beam divergence.
Yep.
> >Other than that, how do you drive these things? Is there some Internet- > >accessible resource where this is explained? Usually, I begin my crawl > >with Wikipedia, but on the subject of driving lasers, Wikipedia is > >surprisingly silent. I'm about to start a search for the datasheet of the > >IC that was in the mouse I tore up, but I fear it might come up empty.. > > Most diode lasers can be driven like an LED, constant-current, or a > voltage and a current-limiting resistor.
The OP could have just opened up a cheapie laser pointer. That would have showed him that they can be driven with three 1.5V button cells, which have such low current capability that they can't overdrive the laser. Slightly less cheap pointers use current-limiting circuitry and can be driven by two AA cells. Another point- some mice use IR (as in it's hard to tell when they're lasing) lasers. Mark L. Fergerson
On Sat, 29 Aug 2015 23:10:18 -0700, nuny@bid.nes wrote:

> On Saturday, August 29, 2015 at 3:07:33 PM UTC-7, John Larkin wrote: >> On Sat, 29 Aug 2015 21:52:50 +0000 (UTC), Aleksandar Kuktin >> <akuktin@gmail.com> wrote: >> >> >I tore up a computer mouse to get my grubby little paws on a laser. >> > >> >Only.. I'm not sure it's a laser. Apart from testing the output for >> >coherence, is there a way to tell a laser diode from a light-emitting >> >diode? >> >> Illuminate a piece of white paper, in the dark. Lasers will show >> speckles. And lasers usually have very low beam divergence. > > Yep.
Hmm, no notable speckles when compared with a known LED.. Guess I'll have to go out and actually buy a laser pointer after all.
>> >Other than that, how do you drive these things? Is there some >> >Internet- accessible resource where this is explained? Usually, I >> >begin my crawl with Wikipedia, but on the subject of driving lasers, >> >Wikipedia is surprisingly silent. I'm about to start a search for the >> >datasheet of the IC that was in the mouse I tore up, but I fear it >> >might come up empty.. >> >> Most diode lasers can be driven like an LED, constant-current, or a >> voltage and a current-limiting resistor. > > The OP could have just opened up a cheapie laser pointer. That would > have showed him that they can be driven with three 1.5V button cells, > which have such low current capability that they can't overdrive the > laser.
Well, I got terribly lazy. :) It was Saturday afternoon, after all, and I was in no mood to get out of the house and go shopping - since I don't have a laser pointer around.
> Slightly less cheap pointers use current-limiting circuitry and can be > driven by two AA cells. > > Another point- some mice use IR (as in it's hard to tell when they're > lasing) lasers. > > > Mark L. Fergerson
A barefoot diode laser has a lot of beam divergence, but it's generally quite asymmetric. The NA is often about 0.15 in the narrow direction (along the laser stripe) and 0.4-0.5 in the long direction (across the stripe). 

That and speckle are the best simple tests. 
(Oh, and blowing up if you look at them crossways, of course.)

Cheers

Phil Hobbs
On Sun, 30 Aug 2015 11:16:15 +0000 (UTC), Aleksandar Kuktin
<akuktin@gmail.com> wrote:

>Hmm, no notable speckles when compared with a known LED.. Guess I'll have >to go out and actually buy a laser pointer after all.
Buying a laser pointer is a good start, but it's more fun to replace the pointer laser pointer head with the laser from an old 16x or faster DVD burner: <http://www.instructables.com/id/How-to-make-a-burning-laser-for-CHEAP/> <http://www.instructables.com/id/Laser-Flashlight-Hack!!/> <https://www.google.com/#q=dvd+burning+laser+pointer> <http://danyk.cz/laser3_en.html> Then, you can do some real damage. It's not quite a death ray, but should scale nicely with additional diodes and better optics. Consider buying some 650nm eye protection before you proceed: <http://www.ebay.com/itm/271499689560> -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Aleksandar Kuktin wrote:

> On Sat, 29 Aug 2015 23:10:18 -0700, nuny@bid.nes wrote: > >> On Saturday, August 29, 2015 at 3:07:33 PM UTC-7, John Larkin wrote: >>> On Sat, 29 Aug 2015 21:52:50 +0000 (UTC), Aleksandar Kuktin >>> <akuktin@gmail.com> wrote: >>> >>> >I tore up a computer mouse to get my grubby little paws on a laser. >>> > >>> >Only.. I'm not sure it's a laser. Apart from testing the output for >>> >coherence, is there a way to tell a laser diode from a light-emitting >>> >diode? >>> >>> Illuminate a piece of white paper, in the dark. Lasers will show >>> speckles. And lasers usually have very low beam divergence. >> >> Yep. > > Hmm, no notable speckles when compared with a known LED.. Guess I'll have > to go out and actually buy a laser pointer after all. > >>> >Other than that, how do you drive these things? Is there some >>> >Internet- accessible resource where this is explained? Usually, I >>> >begin my crawl with Wikipedia, but on the subject of driving lasers, >>> >Wikipedia is surprisingly silent. I'm about to start a search for the >>> >datasheet of the IC that was in the mouse I tore up, but I fear it >>> >might come up empty.. >>> >>> Most diode lasers can be driven like an LED, constant-current, or a >>> voltage and a current-limiting resistor. >> >> The OP could have just opened up a cheapie laser pointer. That would >> have showed him that they can be driven with three 1.5V button cells, >> which have such low current capability that they can't overdrive the >> laser. > > Well, I got terribly lazy. :) It was Saturday afternoon, after all, and I > was in no mood to get out of the house and go shopping - since I don't > have a laser pointer around. >
Digi-Key has 400+ items in their list, just look for "laser". The cheapest was under $6 in single quantity, although that was IR. Looks like the cheapest visible one is about $12 at 650 nm, 5 mW. Probably eBay has them even cheaper. Jon
On Sunday, 30 August 2015 19:57:05 UTC+1, Jon Elson  wrote:

> Digi-Key has 400+ items in their list, just look for "laser". The cheapest > was under $6 in single quantity, although that was IR. Looks like the > cheapest visible one is about $12 at 650 nm, 5 mW. Probably eBay has them > even cheaper.
Another way of getting cheap (infra-red) laser diodes is to buy used SFP optical fibre transceivers on eBay. These can often be bought for around $1 and have good quality drive circuits built in. If you want to modulate them, nost of the work is already done for you. The beam diverges by around 60 degrees in total but is axially symmetric as they use vertical cavity lasers. Most digital cameras can easily see the 850nm versions, but not the longer wavelenght ones. John
On Tue, 01 Sep 2015 09:38:57 +0000, Jasen Betts wrote:

> On 2015-08-29, Aleksandar Kuktin <akuktin@gmail.com> wrote: >> I tore up a computer mouse to get my grubby little paws on a laser. >> >> Only.. I'm not sure it's a laser. Apart from testing the output for >> coherence, is there a way to tell a laser diode from a light-emitting >> diode? > > why is a test for coherence unsuatable? > > https://en.wikipedia.org/wiki/Speckle_pattern
Wasn't aware it existed. Also, excuse me for being away from Usenet for a few weeks. :)
Interesting.

Is it possible that ordinary LEDs have those speckles? Because I think
I once saw those in the light of an ordinary 5mm? red LED. Or was it a
LASER in disguise?

On Sat, 29 Aug 2015 15:07:27 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

>On Sat, 29 Aug 2015 21:52:50 +0000 (UTC), Aleksandar Kuktin ><akuktin@gmail.com> wrote: >
> >Illuminate a piece of white paper, in the dark. Lasers will show >speckles. And lasers usually have very low beam divergence. >