635 and 650/660 PBS?

[gottaluvlasers]

ok, this *may* be a dumb question...

but, why cant we take a 635 and 650/660 and combine it through a PBS? im not talking about combining POWERS. im talking about just using the PBS to combine the 2 beams to some weird combination of the 2 red wavelengths. in other words, some people are talking about using dual wavelengths for red. (635 and 650/660). the dichro for that is what, like $150 or more right? why cant we just use a PBS and lase one of the reds through and lase another one through to combine them at the output as the new combined wavelength red?? i know it isnt commbining POWER, it is for the purpose of combining COLORS. is this a REALLY stupid question?

-Marc

[allthatwhichis]

Heh, I am glad you asked this. I did one day, and it makes me feel better that someone of your... stature asked it also... Of course, buffo answered me.

The answer is yes you can, you can only combine one of each polarity. If you only want a lower powered, duel wavelength red that is cool, but you know we are all power hungry here. We want two+ lasers of each wavelength, two cubes and the dichro.

[Laserman532]

ok, this *may* be a dumb question...

but, why cant we take a 635 and 650/660 and combine it through a PBS? im not talking about combining POWERS. im talking about just using the PBS to combine the 2 beams to some weird combination of the 2 red wavelengths. in other words, some people are talking about using dual wavelengths for red. (635 and 650/660). the dichro for that is what, like $150 or more right? why cant we just use a PBS and lase one of the reds through and lase another one through to combine them at the output as the new combined wavelength red?? i know it isnt commbining POWER, it is for the purpose of combining COLORS. is this a REALLY stupid question?

-Marc

I just wish the pbs cubes were broadband so any color would work with any wavelength. THere are some but a bit pricey...bridge could do them ...may be

[buffo]

Actually, the losses are not as bad as you might imagine. If you've got a PBS cube that is rated for 660 nm red, it will work just fine for 635 nm too. Sure, you might loose an extra percent or two, but that's hardly an issue.

Mark's point is valid - you *can* use a PBS cube to mix the two wavelengths, assuming that you want to expand your color palette.

However, Aaron is also right. The main reason most people don't go this route, and instead opt for an expensive dichro, is that we're all power hungry. In particular, the longer wavelength reds are much harder for the eye to see. Thus you need to get more power out of the deeper reds to make any significant change in your overall brightness. And to do that, you're probably going to have to mix the beams from a pair of diodes to get enough power. (Most direct injection reds in the 650-660 nm range top out at around 200 to 250 mw for a single diode, and you need 500 mw of 660 red to make a dot that appears as bright as just 100 mw of 635 nm red.)

Thus, you decide to use your PBS cube to mix the beams from a pair of diodes to get your deep red, and now you're stuck with a randomly polarized beam. You can't use another cube to mix in the 635 nm red, so you need to use the expensive dichro...

Adam

[Jem]

so you need to use the expensive dichro...

Shameless plug...

I have a 'not quite so expensive' 635/660 dichro for sale from the group buy that is now surplus to my requirements

Jem