Which is best Red laser?

[greenalien]

Red lasers seem to come in a range of frequencies - 635nm, 650nm, 660nm, 671nm. Some are diodes, some are DPSS. What are the advantages / disadvantages of each? Which would you choose for a new projector, alongside 250 - 400mW 473nm blue and 532nm green?

[allthatwhichis]

I'm partial to the 660nm Maxyzmodules. Very nice form factor, great beam specs, and awesome blanking speeds (almost too good compared to dpss ). AND they are made in the US. The only negative I can think of is the power limitation. They come 225mW singles or 400mW duals. He has made a quad 750mW but I'm not sure if there has been a commercial quad model made yet. I bet a quad would go good with 250mW of blue and 150mW of green.

[buffo]

I agree with Aaron. 660 nm is a very nice red, and it has great beam specs. 671 nm red is a DPSS solution, so it also has great beam specs. The problem is that it's costly, and it's very hard for the eye to see, so you need a lot more of it.

635 nm is another solution. It appears very bright to the human eye, so you don't need nearly as much of it, and yet it's still very pretty. Because of the lower power requirement they're also more affordable than the DPSS 671 reds. Unfortunately the beam specs for 635 nm reds are lousy.

So there you have it. The 660 nm solution is a compromise. It's affordable, has good beam specs, and is reasonably visible. What you give up is power. (It's hard to get more than about a half watt of it.)

With the blue and green power levels you mentioned, a 635 nm diode is probably your best bet right now. However, you're going to have to deal with a really lousy beam profile. Only you can decide if you can work with that...

The quad-660 nm solutution that Aaron mentioned would be ideal, but they're not available from Marconi yet. (Maybe by Spring though, if you can wait that long...)

Adam

[laserLips]

greenalien, in case your wondering what makes good beam specs, the guys here are referring to the width of the beam at the aperture, and the amount that the beam spreads out in width over a certain distance. So a beam with good specs is thin and stays thin for longer. Bad specs mean the opposite

Graham, from a noob in know

[greenalien]

Thanks for the responses so far. I'd rather have a red DPSS laser if possible as I understand that the diode type are easily damaged by back-reflection, although a well-collimated multiple 635 diode would also be good if it was powerful enough and the price was right. If 671nm is hard to see, how does that affect the range of colours available when mixing it with green / blue? Is it correct to assume that, if power wasn't an issue,(I have already read posts about the necessary relative powers required from each frequency for a good 'white'), I'd get the broadest spectrum by having red and blue frequencies as far apart as possible, or would there be 'holes' in the spectrum? For example, would 671 / 532 / 457 work or would there be 'missing' colours either side of green?

[allthatwhichis]

No, you would get them, you just add deeper colors and go into dept deeper. My goal is a projector you described, maybe add a couple of blu ray burners in there for that deeep purple.

[stanwax]

I recently saw an RGB with 457 blue in for the first time and the purples and violets were fantastic - really beautiful. I can heartily recommend 457nm blue if your wallet can stretch...

Rob

[greenalien]

I can heartily recommend 457nm blue if your wallet can stretch...

Yes, well, that's always the big 'if' isn't it...

457nm seem to be a lot pricier than the longer wavelength blues and I wonder what their long term reliability is likely to be; I understand that blue diodes generally have a greater failure rate than any other colour despite their higher price, probably because it's newer technology. Of course, as time passes, prices will slowly fall and reliability should go up, just a question of when it's worth taking the gamble I guess...

[Zoof]

Also ~442nm diodes (non dpss) are coming our way as an interesting alternative to 457 dpss. Should be price competative and more stable and reliable. Among others Bocatec has these diodes lasers in their RGB system.