Combining lasers for different colors?

Hello, I'm new to here.

I was referred to this site from another forum, where I found some interesting info about lasers and it wasn't enough to end my curiosity.

Some time ago I saw a youtube video of a person combining two lasers together to make another color, in this case a red and green.

YouTube - Make a yellow laser


I am by no means an expert in lasers, a complete novice if you may. I am wondering about the object, which seems to be like a protractor of some sort that he used to combine the colors?

Is this only possible with that particular object? (Someone kindly let me know what it is called!) As I want to create a yellow laser, instead of buying one of those DPSS units!

Thanks!

Well. It's a protractor, and yes you can combine beams with glass, plastic, or anything transparent (if it's clear enough). If you want to make a hand-held yellow pointer yourself, Jayrob has a great tutorial --> Here

Search white fusion! Combined RedGreenViolet (RGV) is awesome! Full rainbow of colors if controlled properly. Jayrob's build.
Oh & welcome btw.

gaidensensei said:

Is this only possible with that particular object

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It is possible to combine two light beams with every flat and glossy object that transmits some of incident light and reflects the rest of that light. Then, when you cast two beams on this object at proper angles (like that guy in the video) you will get two beams of mixed colors. The problem is that there are two beams - we usually want only one beam as bright as possible. When you have two beams, the light power is divided between them. To combine two beams of different colors into one beam you need a dichroic mirror, also called 'dichro'. Another name for it is interference filter. It is kind of Fabry-Perot interferometer. It is a piece of glass that has transmittion dependent on the light wavelength (thus also the light color). For example, it's good reflector for green light, but red light passes through it without reflection. With this optical element you can combine two beams of different colors into one beam, and the optical power of the output beam is sum of input beams powers (almost, because there is always some loss).

while you should use dichroic filters for perfect combining, those cubes found in sleds will work perfectly to combine 2 beams. BUT, if you need to combine more than 2, then you'll have to jump on to the dichros. And they are usually very expensive

Hallucynogenyc said:

while you should use dichroic filters for perfect combining, those cubes found in sleds will work perfectly to combine 2 beams. BUT, if you need to combine more than 2, then you'll have to jump on to the dichros. And they are usually very expensive

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I want to build a magenta laser by combning BR and Red diodes, do you know where can I buy these cubes?

Make sure you keep in mind that certain wavelengths are brighter to the eye than others, not sure how different BR and red are. Although it mostly applies to green, I don't want you to end up having one color completely overpower the other :yabbem:

Good Luck!

Rafa said:

I want to build a magenta laser by combning BR and Red diodes, do you know where can I buy these cubes?

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.............Cubes are better for combining two lasers of the same color. for different colors use dichros-- tiny ones are inside of laser sleds but their size makes doing this a bit tricky-- bigger(and somewhat expensive) dichros can be gotten from AixiZ on ebay or from companies like Lasever-30$ each-- you need to get the right ones too-- they pass one color and reflect another.. to make yellow you need to combine green and red-- and if the greens too powerful it will not work exactly like you want--so a search here to find out the best powers to use to get the desired balance.

A vet will probably make some corrections to all this as I am still a noob in this area. Cool stuff tho.---HZ

Did YOU hear THAT?? This guy was the "world's first" to make a yellow laser! and it was only summer of last year! If you thought you'd seen a yellow laser before that, your eyes were most certainly lying to you.

They aren't even aligned properly. It's only good at near-field in the vid.

There are plenty of inefficient ways of doing it with solid state, but the best way is a G:R ratio of 1:4 with a dichroic mirror. If you're making a projector, a polycarbonate protractor is about the worst thing you could use. But if you're just looking for proof of concept on a budget, it's about the best thing you could use.

look here and at Lasever.com to see some combining optics. RGB laser beam combining optics - eBay (item 360163990442 end time Apr-15-10 07:15:19 PDT) from AixiZ in Houston with GREAT customer support and quick shipping to US

or from China(long wait often especially during China holidays) 2pcs Reflect Blue Transmission G+R beam combining optic - eBay (item 130371337830 end time Apr-01-10 04:56:05 PDT) with a long wait for shipping and here-- Reflecting Blue Transmission G+R beam combining optic - eBay (item 130371337842 end time Apr-01-10 04:56:09 PDT) I have a set from Lasever-- waiting on a new LPM and some mounts thanks to misterwilling!!! (using leggos turned out to be more hassle than what i was saving)review to follow enjoy--HZ

LOL, i always laugh at all those "world's First" youtube videos .....

@ Rafa: the cube that you find inside the PHR sled is already used for combine violet and red, so it already have the right type of AR coating ..... just remember that the combination depend from the polarization plane of the light, in these cubes ..... as example, aligning it, you need to shine one of the laser through it (the red one) and rotate the module until the more possible light come out from the other side, then shine in the violet and rotate the module until the more violet light is reflected in the same direction of the outcoming red beam ..... then you can align them axially.

HIMNL9 said:

LOL, i always laugh at all those "world's First" youtube videos .....

@ Rafa: the cube that you find inside the PHR sled is already used for combine violet and red, so it already have the right type of AR coating ..... just remember that the combination depend from the polarization plane of the light, in these cubes ..... as example, aligning it, you need to shine one of the laser through it (the red one) and rotate the module until the more possible light come out from the other side, then shine in the violet and rotate the module until the more violet light is reflected in the same direction of the outcoming red beam ..... then you can align them axially.

Click to expand...

I think that a CAD design may help a lot building the magenta laser. But I have to know first if the PHR Sleds cube lets the 650nm light pass at an angle of 45º in one of it sides and reflects at an angle of 45º on the other side all the 405nm light, or if it is another combination of angles. Is that right?

I don't have a cad, but i think a coreldraw and a pair of pics are enough for understand what i mean .....

Here you can see a PHR sled, see how the cube is aligned with the red and violet diodes (i already removed the violet, but marked where it was and the beam directions)



BTW, the element marked "4" is a dichroic mirror that reflect red and violet, and left pass green, so it can be used for obtain yellow (red+green), or bluesky (violet+green), or an RGV assembly (for mix all the 3 colors and obtain the tint you want, including white)



here you can see it better, note how is aligned and the diagonal line where the 2 prisms are glued for make the cube ..... this is the sense in which this cube works better with red and violet:





and here is how you need to shine the beams in the cube, for align them axially and get the magenta that you want:





It's not just matter of angles, is more matter of polarization ..... one left pass the horizontal plane, the other direction reflect the vertical plane, so you need not just to align the beams one over the other, for mix them, but first, find the right polarization for the 2 beams, as i've said before. (the light from a laser diode is ALWAYS polarized)

Cool pics, thanks for posting them. I know that it's difficult to align the beams, so can't I cut this part of the sled (where the prism and the diodes are) and use this part to generate a magenta beam? And by doing this, should I replace the red diode? I guess yes, anyway.

I think i've understood what you mean ..... bare diodes without the lenses, right ?

I already tried something similar here, times ago ..... i reached to combine them, but the result was not too good, also cause the lens is kept too far from the diodes, and as you can see, some glue ended on the PBS, causing a lot of "splashes" around the dot ..... yes, is possible, but not easy (and, once you move the diodes, the alignment is anyway gone ..... where instead, left the diode in position, and you have them already aligned, but you can get from them much less power, cause the optics of the sleds are not made for give you all the power in a beam, but just a round-shaped and aligned beam, so if you use the sled with all its optics in place, you get maybe 20% of the total power, and the rest go lost).

The better solution is to use a pair of aixiz modules, with their lenses, get from them a decent pair of beams, and then mix the already focused beams in the cube ..... you can do this cutting away the cube part, or more easily unglueing it from the sled and glueing it on some plate that hold also the modules with their set screws, or also use part of the sled like in this kit from sightfx (this is a different thing, cause is made for mix all the 3 colors, but the principle is the same, and you can still cut away only the cube part and use it with just the red and violet) ..... or place the modules side by side and use a piece of FS mirror for turn the violet in the cube ..... or any other system that you prefer

HIMNL9 said:

It's not just matter of angles, is more matter of polarization

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Are you sure it's PCBS? When I was playing with this element it looked rather like a dichroic cube beamsplitter. BTW here's a picture of the PHR pickup with description of the elements: http://repairfaq.cis.upenn.edu/Misc/phr803ta.jpg This is what I fugured out about that optics, if there's something wrong please let me know.