638nm laser divergence issue

firelaser · Jun 7, 2013

been searching a lot about the 638nm laser and its issue with divergence at high power, some people wont even get one because of it. For those who own or have seen one how much does the divergence line ruin the laser for you? see poll above and or comment

Eradicator · Jun 7, 2013

I gotta say, my 1 watt 638 shooting through the night sky like a giant red ribbon looks awesome.

You can also get single mode 638's while not as powerful the beam is perfect, and since it has such a tight beam it still looks very bright at only 200mW. Much brighter than a 300mW 650nm to my eyes.

firelaser · Jun 7, 2013

Eradicator said:
I gotta say, my 1 watt 638 shooting through the night sky like a giant red ribbon looks awesome.

You can also get single mode 638's while not as powerful the beam is perfect, and since it has such a tight beam it still looks very bright at only 200mW. Much brighter than a 300mW 650nm to my eyes.

ya id imagine so what would you say is brighter to you your 1W 638 or a 1W blue, or i suppose 1.5 W from your sig ?

Eradicator · Jun 7, 2013

On a normal clear night, the 1.5W is a bit brighter, mostly cause of better divergence I think.

But once a little fog comes in to play, the 638 seems a bit brighter. Its crazy how bright the 638's look in a little smoke or fog.

IsaacT · Jun 7, 2013

I hate the line/dot, but I like the way the beam looks. The line/dot looks very sloppy, like a wide rectangle stacked on top of a less wide square. The beam is pretty cool though, wide and intimidating. But only if you cannot see the line/dot. I had one but I sold it to make a single mode, if that tells you anything.

Eradicator · Jun 7, 2013

Ya, I didn't think about the dot. 90% of my laser viewing is outdoor beams, so I don't look at the dot too often, and when I do its usually 100+ yards away.

Its definitely a sloppy dot, and there is quite a bit of splash as well.

firelaser · Jun 7, 2013

so... when i do get around to getting one which would you recommend? getting a single mode one around 150mw or so or the multimode with a 800mw + power..

Eradicator · Jun 7, 2013

That comes down to personal preference. You will probably spend a little less on the single mode build though. I, personally, try to get every diode so I would say both.

chipdouglas · Jun 7, 2013

100% non issue for me. when you shine it in the sky you cant even tell. now if youre pointing around you get a rectangle bar.

Michael.

Laik · Jun 8, 2013

I am currently saving for a 500mW 638nm Mitsu diode to put in a kryton groove

It sucks though because to get 500mW out of them they are about 644nm. To get 638nm you have to give them 600mA which is only about 300mW. I'm not sure what i want to do :thinking:

Eradicator · Jun 8, 2013

I don't think they really drift that much with a decent heatsink, there is an obvious difference of color between my 1W 638 and my 1W 650, so it cant have drifted that much or you wouldn't be able to tell them apart.

The 638 is also twice as bright at nearly identical power.

Just4FunReally · Jun 8, 2013

Eradicator said:
I don't think they really drift that much with a decent heatsink, there is an obvious difference of color between my 1W 638 and my 1W 650, so it cant have drifted that much or you wouldn't be able to tell them apart.

The 638 is also twice as bright at nearly identical power.

You also have to remember that the 650nm diode is drifting to longer wavelenghts as well as it heats up. Here's an output chart for the 300mW multi-mode Mits diode. According to the tests Cypa ran on these two, they mark them as 300mW diodes because that's when it's 638nm. I'm assuming the 500mW one has significant increases as well after the recommended current is passed.

jimmy009 · Jun 8, 2013

638nm laser is quite awesome, ready to buy one

firelaser · Jun 9, 2013

jimmy009 said:
638nm laser is quite awesome, ready to buy one

as am i, i got Green and blue but it may be time to go sith lord lol

Eradicator · Jun 9, 2013

Just4FunReally said:
You also have to remember that the 650nm diode is drifting to longer wavelenghts as well as it heats up. Here's an output chart for the 300mW multi-mode Mits diode. According to the tests Cypa ran on these two, they mark them as 300mW diodes because that's when it's 638nm. I'm assuming the 500mW one has significant increases as well after the recommended current is passed.

Thats a different diode, were talking about the 500mw version, there is two different Mitsubishi multimode 638 diodes, the diodes used to reach 1W have much less wavelength drift. Also, that is tests on two diodes, each diode is unique though, some much more efficient than others.

Just4FunReally · Jun 10, 2013

Eradicator said:
Thats a different diode, were talking about the 500mw version, there is two different Mitsubishi multimode 638 diodes, the diodes used to reach 1W have much less wavelength drift. Also, that is tests on two diodes, each diode is unique though, some much more efficient than others.

Hence the part in my comment, "I'm assuming...". Yes, I'm well aware that they are different, but seeing as they are produced by the same manufacturer at the same wavelength, the only difference being the amount of output they can release, they MAY have some similarities.

Also, this official datasheet for the diode says that at a max current of 800mW (I'm well aware that they can take more, but this is the max recommended current that they tested it at) the wavelength would go as far as 644nm. At > 1A I'm pretty sure that can reach near 650nm.

EDIT: In case it's hard to find, I was talking about the second grid, the third and sixth rows, in the "max" column.

638nm laser divergence issue

638nm laser divergence issue

i actually like the line/dot

it bugs me a little but can deal with it

it is pretty bad but i can would still get one

i cant stand it i can only have a single mode one

i have never seen 638nm

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