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Sharp 490nm GH04850B2G 55mW Laser Diode

kecked

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So what happened with the two lines. Did you ever measure them. Ahhh Necro posting.
 



cappernicus

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What do people recommend to be the max running current for these? I've looked everywhere and can't seem to find any good information. I can't even find the wiki that someone put up years ago for the various diodes.

In particular, if anyone has killed one what current was it running at and in what kind of host?
 

paul1598419

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I have binned many of these diodes by wavelength and, though I have never killed one, they seem to work well in currents up to 300 mA. Most of mine are set to 275 mA, but since the forward voltage on these are fairly high it is important to heat sink them well.
 

styropyro

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IIRC they are rated for 135mA max and I personally never push them past that. When you go much higher than that you never know if it'll fail quickly or not. It seems a lot of people drive the piss out of them without issues though, and thankfully they aren't super expensive to replace if they fail. To each their own!

Oh yeah, I batch tested some of these on a recently calibrated Ocean Optics Torus spectrometer. The new batches have a different can number and are slightly bluer and lower in variance than the old batch. The measurements of the old batch (labeled "o") do not accurately represent the population as I cherry picked the greenest and bluest diodes before I obtained a spectrometer. The new diodes were from techhood, and they accepted an offer of $25 per diode in quantities of 5 or more on eBay. All measurements taken at 90mA drive current. No thermal regulation was used so take the data with a massive monocrystalline slab of sodium chloride.

A couple of the diodes showed two distinct wavelength peaks on the spectrum, so I reported the average wavelength there.

488test.png
 

paul1598419

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Wow! I have binned many of these diodes, but have never seen one measure 485.anything nm. That is remarkable in my view. These diodes tend to shift more with temperature than drive current from my tests with them. Are you certain of the spectrometer's calibration?
 

RedCowboy

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Wow! I have binned many of these diodes, but have never seen one measure 485.anything nm. That is remarkable in my view. These diodes tend to shift more with temperature than drive current from my tests with them. Are you certain of the spectrometer's calibration?
paul you said that you don't heat sink the diodes and only drive them just above threshold when observing the wavelength via spectrometer, you should use a non press fit sink and drive them at spec and normal operating temp, then you would see what the wavelength is as per the diodes design which would be a more accurate assessment because nobody is going to use them at barley lit threshold.
 
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paul1598419

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I said I have not always heat sunk diodes when binning them. When I have done this it is only for about 2 seconds. Not nearly enough time for them to heat up, but I have measured the low wavelength ones in large heat sinks at currents from 75 mA to 300 mA. They are quite stable when done this way.

At any rate, lower currents would effect these as showing lower wavelengths not higher ones. The lowest I use is around 50 mA which is a bit above threshold.
 

styropyro

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Wow! I have binned many of these diodes, but have never seen one measure 485.anything nm. That is remarkable in my view. These diodes tend to shift more with temperature than drive current from my tests with them. Are you certain of the spectrometer's calibration?
I actually have a diode very close to the 485.0nm mark (as also measured by kecked at SELEM) but I don't know the drive current so I didn't report it here. Dr.Laser has a freak diode that came in at 480nm! I'll check the calibration on my spectrometer sometime soon to be sure about those measurements though.

For the record, I did take my measurements with the diode in a heatsink, I just didn't use any temperature control to lock the diode to a set temperature.
 

paul1598419

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I actually have a diode very close to the 485.0nm mark (as also measured by kecked at SELEM) but I don't know the drive current so I didn't report it here. Dr.Laser has a freak diode that came in at 480nm! I'll check the calibration on my spectrometer sometime soon to be sure about those measurements though.

For the record, I did take my measurements with the diode in a heatsink, I just didn't use any temperature control to lock the diode to a set temperature.
Yeah, I'm aware of that 480nm diode. It was from a small batch of diodes from Sharp that came to us first. Most measured between 473nm and 478.8nm, but one or two squeaked through to 480nm. That was the only diode that I didn't save any spares from. I'm still kicking myself for that. See my 477nm one in my signature.
 

kecked

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I promise that diode is as advertised. Not only was my spec calibrated, it was obvious by eye.
 

paul1598419

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I promise that diode is as advertised. Not only was my spec calibrated, it was obvious by eye.
That's great! I had no idea some of the newer ones got that low. I might have to see if I can get my hands on one. Thanks.

The lowest one I had was 486.5 and I gave the build I made with it to my daughter. It is her favorite wavelength.
 

cappernicus

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Thanks for the responses. I usually try not to push them to their max, but I do like to know where the realistic limits are. With this one I was hoping to hit 100mW with a standard 3-element lens but it looks like that's going to be too high. Since I asked, I looked at DTR's string of images from his initial test and compiled a graph, just in case it helps anyone. (Pardon the poor image quality - I had to shrink it to upload)

Several years ago I remember reading that one way to determine a relatively safe max operating current was to look at the current vs. output graph and run it just below the first knee in the graph. Granted, this was before the greens came out when all the diodes tended to die suddenly rather than level out and dip at the end, but I assume that the same would still hold true. What do you y'all think?

Ignoring the fact that diodes vary somewhat, this puts the max recommended current at about 285-300ma, which seems to match the general consensus. Still, I am very curious to know the typical expected run-time at that current.

Sharp-488.jpg
 

paul1598419

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Those Sharp 488nm diodes will give you a good >100 mW output when used with the acrylic lenses you get free with any module purchase. These also tend to reduce the rectangular artifact at the very least or remove it entirely. All of mine have no artifacts with the acrylic lenses.
 

cappernicus

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That would make sense based on the power measurements I graphed from DTR's data, even though he uses a G2 lens, but using my old laserbee meter and the 3-element lens I wasn't seeing that kind of efficiency. I guess my meter is reading low and needs recalibrated. I've been hoping to get a thermopile based meter but alas...
 

paul1598419

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Yeah, as I recall the only Sharp diode I had real trouble getting rid of the artifact on was my 502nm one. I believe I used the DTR 2 element 520nm AR coated lens for that one. Still got a reasonable 110 mW out.
 




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