Laser Diodes-Surge Damage Prevention

[MARK]

Hello friends

I read an interesting article on Surge Damage and wanted to share the information.
I'd love to hear comments from you about the article.

Sorry in advance for my poor English.

 

[Pangolin]

Dear Mark,

This is a great article and I thank you for sharing it with everyone here on Laser Pointer Forums!

As I reviewed the article, I certainly agree with everything written here. Many of the precautionary measures such as shielding, adding additional resistance to probes and test equipment, etc. are all good ideas. However they are also at least somewhat inconvenient.

With the exception of very slow and very long events, such as someone slowly ramping the current up beyond what the laser diode can take, we believe our LASORB device would prevent laser diode damage even in the face of all of the causes mentioned in the article, but without the need to do the additional inconvenient things mentioned in the article. You can check out LASORB, and also learn additional perhaps even surprising things about laser diode failure and ESD at LASORB - ESD absorber for laser diodes

Best regards,

William Benner

 

[MARK]

Dear William,

Thank you for your reference.

How about the possibility of using TVS diode (SLVU2.8) instead of LASORB ?

http://www.semtech.com/images/datasheet/slvu2.8.pdf

Thank's Mark

 

[lasersbee]

Hello friends

I read an interesting article on Surge Damage and wanted to share the information.
I'd love to hear comments from you about the article.

Sorry in advance for my poor English.

Nice article....

From what I read I understand that the Surge Damage can
be caused in APC circuits by the time delay between...

1) applying current to the LD
2) the LD outputting Photons
3) the APC Photo Diode detecting the LD's output power
4) the APC circuit taking corrective measures...

There is a time delay in the APC that can cause a startup
surge.

The Drivers we use here are basically not APC and are
pre-adjusted to a known current..


Jerry

 

[MARK]

Some examples also refer to diodes without PD (photodiode).
You can download the complete article to read.
http://www.opnext.com/products/pdf/ode5001_surge.pdf

 

[Pangolin]

@Mark: Great comment and great thought. But here's the situation.

First let me say that Pangolin never really intended to get into the field of laser diode protection. That was never our first thought. We only wanted to make a great laser diode driver. On our journey to accomplish that, we tested a lot of ESD protection approaches. We tested everything that had been done up until that point in time, and also all of the obvious things such as TVS. We thought ESD protection would be the easiest part of the project, and that we would get on with our lives rather quickly. Much to our surprise, that was not the case. In the end we spent over a year perfecting the approach that we now package and call LASORB.

Regarding specifically TVS, what these do is essentially try to "clamp" the voltage to a particular level. Even if they could do this, tell me, what clamping voltage would you choose? One that is just above the highest voltage of the laser?

Well, this is where Laserbee's comment comes in. He very keenly reads that in many cases, the APC circuit is too slow, so the laser diode driver itself will apply too much current. As you may know, the voltage of the laser diode changes very little once the laser diode hits threshold, so even choosing a TVS voltage close to the maximum is generally too high.

Also, as you know, TVS only come in certain voltages, not every single voltage in tenth-volt increments, so it's really not possible to choose a perfect one for the job.

And lastly, the voltage across a laser diode changes as the temperature changes. This is another complicating factor.

Best regards,

William Benner