SUPER FREAK "445nm diode"

[Garoq]

Maybe they have old stock left over and they are mixing in the old with the new. This could be why we are still see average diodes.

Could very well be. There is a distinct difference in average power between the diodes from the previous A-series and this latest one. At this rate I may go back to A-series for all the diodes and save a few bucks.

 

[clif]

Could very well be. There is a distinct difference in average power between the diodes from the previous A-series and this latest one. At this rate I may go back to A-series for all the diodes and save a few bucks.

Yeah no kidding!

 

[Garoq]

It's interesting - I've said this to both Lazeerer and DTR before - but I don't really believe the H-series has different diodes than the M. I'm even going as far as to say that I believe if you bought an A-series that was manufactured TODAY (they're still making them), we'd get these same diodes in them.

That's what it is starting to look like. Only time will tell after repeated harvests of the newer units.

 

[Seoul_lasers]

Nah. I get 2W diode all the time.

All my 2W laser are still going strong. Have never seen one even Degrade at all. Some of my 2W laser are over 1 year old and those 2 i use the most and run them for long Duty cycles.

So If all my other 2W lasers are set to 1.76A and putting out 2W+ and this one at the same currant is putting out >2.5W it will still have the same Long life as my other ones. Possible more because its so efficient.

I have yet to hear to this day a 2W laser dieing from natural causes

This is the same kind of performance from my A140 diode lab laser setup I observed.
I used the Die4driver (1.3v) at 7.6VDC input (4.9VDC to the diode) and off the monitor side I had a current of 1.86A into the diode. Since I don't have my own LPM, I took it to my University where it measured off an Coherent LMP (fieldmax II) at the Physics dpt. at around ~2.3W peak. Averaging around 2.1-2.2W.
I don't think 2.4W is a stretch. Some diodes are better than others. A130 is by far the lower performer diode.

 

[Jubathoph]

Guys how accurate are these LPM's as a function of wavelength and power? I would think that they would have different absorption characteristics based on wavelength... Any ideas?

 

[Bluefan]

Coherent stuff is probably quite accurate, I wouldn't worry about that. The absorbtion may vary a percent or 2, not much more. It probably can be looked up in the datasheet of the power meter.

 

[Garoq]

Guys how accurate are these LPM's as a function of wavelength and power? I would think that they would have different absorption characteristics based on wavelength... Any ideas?

I'm not an expert on LPMs but I suspect that the sensor coatings have broadband absorption characteristics. Jerry/Lasersbee would be the one to comment on this.

 

[cilegray]

No my bench will only give 5A and the power brick out of the A140 does right about 10A. That is about it for what I can provide to it.:cryyy:

You could always just pick up a cheap ATX PSU with a good +5v line and jump pin 14 to ground to power it up.

 

[clif]

I think TEC and thermal sensor heads both measure the heat absorption from the laser light, regardless of wavelength, in most cases. Gary's right - Jerry would be a good one to chime in, or Johan with bluefan.

 

[rhd]

I think TEC and thermal sensor heads both measure the heat absorption from the laser light, regardless of wavelength, in most cases. Gary's right - Jerry would be a good one to chime in, or Johan with bluefan.

Yes/No

Think of it this way, if your LPM was white, and you were trying to LPM an IR laser and a 405nm laser, and both were the same in terms of mW output, you wouldn't get the same readings. We know that white does a poor job of absorbing IR wavelengths.

Now, LPMs are not white of course. But the same principal could very well apply to a black surface, even though you wouldn't expect it to be that pronounced. And certainly, with an LPM sensor's surface, you'd expect them not to just use any old paint/anodizing/coating without verifying that it had as even an absorption as possible of the various wavelengths it would be used to test.

 

[Bluefan]

Nearly all thermal power meters measure the temperature resulting from absorbing the laser light. Pyroelectric power meters measure the change of temperature, so these can only be used pulsed or chopped.

The coating will need to be spectrally flat, all wavelength should have equal absorbance for the calibration to be valid over that wavelength range. No coatings is 100% flat unfortunately, and damage thresholds and stuff also comes into play when making a coating. Newer lpm's thus still have a calibration setting for the wavelength for the few percent difference in absorbance.

Coherent has 3 primary coatings, it really depends on the coating in question. From what I can find their power meters are actually calibrated at 514nm, not the 1064nm I'd expect. The difference in absorbtion between the calibration wavelength and 445nm is a litte over 1% for their broadband coating, nothing special. The normalized curves can be found in their catalog. Their "black" coatings looks almost flat in the visible range (~0.25%).

 

[Benm]

Nothing is perfect ofcourse, but as stated above, the variation around the visible spectrum needn't be that much. I wouldn't expect 0.25 on all lpms, but it won't be more than a few percent on any thermal lpm unless it was build really badly.

 

[rhd]

Hey guys. I was playing around with one of those variable magnetic hosts. It was tedious process that didn't react well to test loads, so I used a real 445 - one of the middle of the road binned output diodes.

Anyway, long story short, in the process of doing this, one of the magnets I was manipulated the driver with flew out of my hand and onto a battery cell, which placed it in a way that caused the driver to unload way too much current into the 445. I watched in horror as the current on my DMM (in series with the LD) hit 2.6A.

It was only that way for a few seconds, but I thought the diode was toast. It happened too fast for me to really see if the diode had died in the process, so I brought it back to my bench PSU. The diode worked. So, out of curiosity, I cranked the current back up to 2.5A.

The diode was just fine. I left it shooting at my Ophir sensor for 20 seconds or so, and no issue. With a G1, not "perfectly" aimed, it was reading 2.5W. This was a middle-of-the-road diode.

It definitely had a minimal benefit to run it at 2.5A over say 2.2A, but there was undoubtedly a benefit to running it at 2.2A over 1.8A. That jump from 2.2A to 1.8A was certainly meaningful in terms of output.

2.5W from a diode that wasn't "crazy awesome" in terms of binning. I'm going to go grab a high binned diode and try the same. I'm hoping it's not a fluke, because I'd hate to loose a high binned diode. But I'll report back.

EDIT:
- Basically the same deal with the higher efficiency diode. It was completely happy at 2.5A kicking out 2.7W on the Ophir. Somewhere around 2.1A seemed to be the sweet spot, with it holding about 2.5W.

 

[Wolfman29]

Haven't we been under the impression that these generally die at around 2-2.2A?

 

[lazeerer]

Ive never seen one not dim out after 2.3A. Not die but din out.... Hmmmm Intresting...

Was this with an H Series diode.?

 

[rhd]

Ive never seen one not dim out after 2.3A. Not die but din out.... Hmmmm Intresting...

Was this with an H Series diode.?

Yep, they both were.

I would be interested to know what the point of dimming would be. I suspect it is right around 2.5A (for these two diodes). It was pretty marginal from 2.3 to 2.5. I think the elbow is probably around 2.5A.

I'm going to keep setting these around 1.8, just because I feel more comfortable justifying that current until there's some more data to back up pushing it to 2A.