Got Red?

[buffo]

Why can you not combine 2 randomly polarized beams of the same wavelength into a non polarized BS cube?

Quazar is right. To expand on how this works, think about how a PBS cube works. You've got one face that will accept a randomly polarized beam and will split it into the horizontally polarized and verticaly polarized components. Now, if you reverse that, you can combine two beams into one.

But if you send a randomly polarized beam into the face where you normally send a verticaly polarized beam, then the horizontal component of the beam will pass right though to the 4th (unused) face and be lost. Likewise, if you send a randomly polarized beam into the face where you normally send a horizontally polarized beam, half the beam (the vertical component) will again be reflected to that 4th (unused) face on the cube.

The result is that you'll still have two beams exiting the cube, but each beam will be made up of 50% of the power of each incident beam. (Minus optical losses in the cube) So it's pointless. Once you have a randomly polarized beam, the only way to mix it with another beam of the same frequency is to position the two beams really close together using a knife edge mirror, like the Arctos units do. (Now, if you want to mix it with a *different* frequency, you can use a dichro.)

Adam

[steve-o]

Ok, why horiz and vert only ? Thats 90 degrees. theres 360 degrees in a full circle..
Why not polarize something at 275 degrees, or 45?

[buffo]

90 degrees is the same as 270 degrees, and 180 degrees is the same as 0 degrees. Remember that light is a wave, so it vibrates up as well as down. A vertically polarized beam is one where the light waves are vibrating up and down. Horizontally polarized light is vibrating left and right.

If you try to split hairs and do the 45 degree polarization angle trick, you run into a wall. Without going into the quantum mechanics of it, if you send a vertically polarized beam through a polarizer set at 45 degrees, *half* the beam will make it through. Same thing goes for a horizontally polarized beam. So the minimum separation angle is 90 degrees if you want 100% discrimination between polarization angles. Unfortunately, 90 degrees is also the maximum separation you can have between any two beams, because they vibrate up and down (or left and right). So 105 degrees is the same as 75 degrees, and so on...

If you really want to dive in, have a look at this article from Scientific American. (It was in the April issue) They show you how to use polarizing film to explore the wierd world of quantum mechanics (and specifically, how to build a "quantum eraser" that can erase "which way" information from a dual-slit experiment *after* the light has passed the slits!) It's great reading, but if you're not into quantum mechanics it will make your head spin... You've been warned!

(And no, I haven't tried the experiment yet. It's on my to do list, however.)

Adam

[lasertony]

For those who are interested in the Mitsubishi diodes... I've tested them.
Unfortunately the divergence of this 150mW diode is about 10°x40°. This means you can not use a single lens to collimate it into a dot. The main problem is the fast axis: 40° is about the double of other diodes at 650-660nm in a 5,6mm can. Trying to put these in a Marconi modules results in a line instead of a round spot being projected onto a wall 10 meters away.
And more: because of the 5,6mm housing it is impossible to use fast axis collimation very close to the diodes' emitter...
So unless you intend to use only 1 or 2 with a slightly more complicated setup this diode is unusable to combine 4, 8 or more the 'Arctos' way...

Thought you'd like to know.

[steve-o]

Thanks You-all , the chances of this happening is starting to look slimmer and dimmer... heh, well there's always the ol' 88 beam (Marconi-quad type) , kinda fat but bright ..
Adam- I think I'll spare myself the quantum mechanics for this monday morning 1st thing..ugh..

[steve-o]

The dual 635+dual 660 combining does sound intriguing, though; the 635s and the custom dichro might be $$$ ..more into the 'pit', heh..
_____________________________

How do you match a diode with the correct collimator? Slow axis/ fast axis numerical aperature (if applicable) and all that kind of stuff?

[steve-o]

Back to the other topic- Interesting pic on the German section of Laserfreak- I just loves them groovy mirror mounts

[liteglow]

Cant maXyz make small modules like that ?
I want to make 4 or maybe 6 red lasers into one beam..
2 and 2 togheter into a qube, and paralell 2 beams..

That will give me 1Watt red (if I use mazxyz moduled)
But The big black heatsink take much place for that job !

And the maxys is not parlell mounted inside the black heat sink...

[steve-o]

My guess would be a heat dissapation issue; You can run them for a while with no baseplate mount for testing, alignment,etc. Also he has the driver circuit in there too. Other than that, I would imagine that the diode/ collimator is about that size. They have a pic of one disassembled on their website here
I wish they still made the green ones *sob*

[steve-o]

Rob (Stanwax) built a nice small dual setup, maybe he will shed some light on the construction of these