First laser module build... failed

[Finale]

I got the Oclaro 700mW red diode in a brass housing with G2 lens, soldered the wires to a 5A driver (Simpledrive) by seller x-wossee (Vladimir), the brass housing was bolted to a large aluminum heatsink with a fan blowing through it. The driver was also attached to a large heatsink. Power supply was set at 11V and could give up to 30A.

The 5V signal was coming from a 5V power supply, so it was on all the time.

I followed the instructions which came with the driver and set the bias first, then powered it all up again and started setting the beam power. I had a power meter (laserbee) and I got up to 650mW. Strangely the power started dropping when I tried increasing the current, so I didn't. But from DTR's pictures and info here I should have been able to drive it way above that.
The housing was barely getting warm.

So anyway, I tested it few times again and it was producing the same beam.
Today I powered it all up again and this is what happened: the beam showed up at full power for less than a second, then quickly much much weaker. I don't know if that is what we call "weak LED-like glow" of dead diodes or not. It was just 8mW power.

I understand that I might kill one or two diodes as I learn and this $20 diode was for testing purposes anyway. I just want to understand what might have gone wrong so I won't repeat the same mistake again.

[kecked]

Sudden infant diode death

Happens. Check for spikes in that voltage supply. Drop the vcc to say 6v. You don't need 11v. Which is. Weird value anyway. You also didn't add the much needed lasorb. Sounds like it got a static charge some way in handling.

I had this issue with a poor power supply. Fortunately this was an inexpensive diode. I did this several times on 300.00 diodes. That's when 35mw reds just came out...... they have gotten much better since.

That lasorb will save you years of headaches.

[kecked]

One last point don't have the modulation on when you turn on the power. That is an invitation to trouble.

[epyn]

How long was the lead between the driver and the diode? This should not be more than 20 cm and roll up them.
Did You use Lasorb?
Is the PSU working correctly means it is a quality one?
Vladimir's driver has start up delay to prevent the PSU's start up transients?
I have Dave's LSP driver and never ever killed any laser diodes.
Oclaro diode is feedable up to 1200mA with active(TE) cooling, i'm using them at 1100mA @ 20C°(TE cooling) Are you measured the current on the diode or just the optical power?

[Finale]

How long was the lead between the driver and the diode? This should not be more than 20 cm and roll up them.

Can you explain this? The cables are a bit longer, around 30cm.

No Lasorb, but this diode I think has builtin ESD protection and I was wearing an ESD wriststrap when handling the parts. Can ESD happen "by itself" when all the components are on a ESD mat and I don't contact them?
I think I read somewherein this forum that the reds are pretty durable. But it does look like it.

The driver has startup delay of about 1 second.

11V because I was using a 12V PSU and lowered the voltage with the trimpot to the minimum possible (11)

One thing which I should have done was measure the current as I was adjusting the power... I only relied on power meter and the temperature of the housing.

thanks

[kecked]

Can you explain this? The cables are a bit longer, around 30cm.

No Lasorb, but this diode I think has builtin ESD protection and I was wearing an ESD wriststrap when handling the parts. Can ESD happen "by itself" when all the components are on a ESD mat and I don't contact them?
I think I read somewherein this forum that the reds are pretty durable. But it does look like it.

The driver has startup delay of about 1 second.

11V because I was using a 12V PSU and lowered the voltage with the trimpot to the minimum possible (11)

One thing which I should have done was measure the current as I was adjusting the power... I only relied on power meter and the temperature of the housing.

thanks

The longer leads add inductance and also pickup noise that can make problems. Your prob fine. Yes they can just die on the birthing table. You only need a very short read millisecond long pulse to toast your diode. That is why I say not real good to have modulation on and the circuit calling for current until the circuit settles down. That takes a few ms and that can be enough to make problems. It's rare but so is your issue. It might not happen and it might never have happened. Just offering ideas.

id just change diodes and move on.

[epyn]

Oclaro 700mW Diode has not built in protection. The newer generation 450-465/520 nm diodes have.
The shorter cables advantages are above.
If you twist (i think this is the proper word... ) the cables you get an 'electromagnetic shield'
The two wires attenuate the unwanted signal noise even an unbalanced lead pair (signal+GND wires)

You are the biggest ESD threat to the diode especially in a room with rug.
When i playing around a diode my first step is shorten the pins with iron. Putting into the mount soldering the LASORB and finally unsolder the shortened pins. If i don't have Lasorb i'm using schottky diode in unparallel ,a 470 ohm+1uF capacitor combo glued to the top of the diode mount.
Always works.

[dkumpula]

Hey Finale,

Sorry for your loss. It happens to all of us, but it sucks whether it was a $3 diode, a $30 diode or a $300 diode. I do have two alternative explanations for what might have occurred for future reference based on my hundred or so purchase from DTR.

First, you may have gotten a diode that simply couldn't handle the current that a typical one in the lot does. I've had a few (mostly blue and green single-modes) that just didn't perform like they should have. Replacing with a different diode while keeping everything else the same worked. For each diode, I start with a lower current and then ramp up it up slowly while watching the output on a laser meter to see if its peaking out. If it starts dropping, I quickly turn down the power before the diode is damaged.

Alternatively, you may have received a module from DTR where the diode wasn't fully pressed in. This has happened a few times to me, but I have diode presses that I use to correct the issue. Left unfixed, you'll get a colimated beam where you can see the 'skew' as the beam is going through the lens at an angle. It also results in lower power as some is lost within the module. I've seen something similar that appeared to be a defect in the diode itself, but I don't have a proper microscope to see the error.

Either way, it won't help you in this situation, but you can keep your eyes open in the future.

-David

[Finale]

If you twist (i think this is the proper word... ) the cables you get an 'electromagnetic shield'
The two wires attenuate the unwanted signal noise even an unbalanced lead pair (signal+GND wires)

Is the 'electromagnetic shield' created that way helpful against ESD? Or are you suggesting to do this for the driver's 5V signal cables?
I actually do twist the power cables of the diode and driver, but just to keep the projector insides tidy.

For each diode, I start with a lower current and then ramp up it up slowly while watching the output on a laser meter to see if its peaking out. If it starts dropping, I quickly turn down the power before the diode is damaged.

Do you also measure the Amps while doing this, or just the laser power?
I did the same when I noticed the power dropping.

thanks

[epyn]

Is the 'electromagnetic shield' created that way helpful against ESD? Or are you suggesting to do this for the driver's 5V signal cables?
I actually do twist the power cables of the diode and driver, but just to keep the projector insides tidy.

In short no. It's against the noise that the long cable can picking up in a small signal system(audio for eg.)
I'm always twisting the cables not just for the above. Looks tidy and sorted.
To prevent any ESD failure ,Lasorb is needed for every diode.