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ArcticMyst Security by Avery

Overdiving CW laser with 100nm pulses

a12b34c56

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Sep 5, 2019
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While it is a well known fact that LEDs can be overdriven when are run in pulsed mode generally it is not recommended to overdrive LDs. I found a number of papers which report that various CW LDs can reliably produce up to 30 times higher output in pulsed mode when driven with <10nc pulses. I wander if anybody tried to overdrive LDs with 100-500nm laser pulses? I’m thinking about running them at twice recommended current.
 





kecked

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I read something similar. Not all diodes can handle it. I’m not an expert on this. I did try it and the diode lasted a few weeks. The shortest pulse I could get was in the 100ns range. The real trick is making such short pulses that rise and fall fast enough. Capacitance is your enemy.

there are standard pulse shaping circuits they just need careful construction. One idea I didn’t try was holding the diode just below lasing with a dc voltage and then putting the spike on top. Idea being the conduction happens faster. The rep rate also needs to be low enough to let the laser recover.

interesting project enjoy.
 

a12b34c56

New member
Joined
Sep 5, 2019
Messages
15
Points
1
I read something similar. Not all diodes can handle it. I’m not an expert on this. I did try it and the diode lasted a few weeks. The shortest pulse I could get was in the 100ns range. The real trick is making such short pulses that rise and fall fast enough. Capacitance is your enemy.

there are standard pulse shaping circuits they just need careful construction. One idea I didn’t try was holding the diode just below lasing with a dc voltage and then putting the spike on top. Idea being the conduction happens faster. The rep rate also needs to be low enough to let the laser recover.

interesting project enjoy.
I think it is doable to get < 100 ns pulse if LD is soldered to the PCB that has a driver circuit so the capacitance is minimal. This is what they do with LIDARs and with RF applications. I believe they use pulsed 950nm Osram LDs that can do 75W in pulse but the pulse is shorter than 60 ns. The circuit is very simple and is based on avalanche transistors. Pulsed 25W 950 nm LDs are pretty cheap but I need 808 nm for my application and I could not find any pulsed LDs.

People on Arduino forum told me that any LED can be overdriven but highly I doubt it as I found a bunch of LEDs with data sheets that don;t specify pulsed operations. I run some red Osram LEDs with 50% over CW rating with 200-500 ns pulses and 10% duty cycle but I don't think my total run time is more than 10h.
 




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