[Laser] Re: Laser digest, Vol 1 #92 - 1 msg

Sun, 3 Nov 2002 14:53:29 +0530

You can regulate the current pulse to make the laser diode safe. Also it is
better to operate it in pulsed mode. Use PC's parallel or serial port to
produce data for it.

shyam

----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: Sunday, November 03, 2002 2:31 PM
Subject: Laser digest, Vol 1 #92 - 1 msg

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>    1. Laser diode characteristics. ([email protected])
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> Message: 1
> From: [email protected]
> Date: Sat, 2 Nov 2002 20:36:52 EST
> To: [email protected]
> Cc: [email protected]
> Subject: [Laser] Laser diode characteristics.
> Reply-To: [email protected]
>
> Hello group.
>
> After building a couple of simple transmitters based on laser pointers and
> just replacing the mercury cells with a regulated supply of the same
voltage,
> I'm now trying a circuit with discrete 650nm diodes. Hopefully this will
> increase power output.
>
> However, in being very cautious, I've noticed that as I slowly increase
> current up to the lasing threshold the device begins to emit laser light
but
> after about 30 seconds at that current level, the light output decreases
and
> becomes non-coherent again.
>
> Question........Am I seeing an effect which causes the lasing threshold to
> change as the device warms up?     And is this a normal characteristic?
>
> If I switch the device off, wait for two minutes and try again the same
thing
> happens, so I haven't killed it.....yet.
>
> Finally, the laser output power appears to increase very rapidly once the
> threshold is reached. Without an optical power meter it's going to be very
> difficult to judge if I'm still within the safe limits. According to the
data
> sheet the operating point may be anywhere between 28 and 48mA.  Is there a
> good rule of thumb I can follow e.g. Threshold + 5% is OK but +20% = dead
> laser diode?
>
> I should add that this is with a cheap 5mW diode, but I have a 20mW device
> which I really don't want to destroy by doing something silly.
>
> Thanks
>
> David  G0MRF
>
>
>
>
>
>
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