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# Reference Guide: How to Combine Lasers

#### ARG

##### Well-known member
This is a brief reference guide on how to combine two lasers into one. I will only cover the basics here and not go into much detail. In depth info is available here: http://nqlasers.com/scannerreference/index.php?title=Main_Page

Credit goes to things for the awesome diagrams!

There are three main ways to combine beams:

Knife Edging

Common use:
Combining lasers of the same wavelength multiple times.

Description:
Knife Edging is the method of stacking beams next to each other. This can be done as many times as desired.

How to:
Multiple laser diodes are lined up in a row, and reflected at a 90° angle by a mirror positioned at a 45° angle. This stacks the beams closely next to each other, giving you a larger but more powerful beam.

Diagram:

Picture:

Can combine multiple beams.

Creates a larger beam.

Dichroic Filters

Common use:
Combining lasers of the different wavelengths once.

Description:
Dichroic filters reflect a beam of one wavelength and transmit a beam of another wavelength. You can only do this once with each wavelength.
Example:
You can not combine 532nm and 660nm together, then combine that beam with 660nm again.
Example:
You can combine 660nm, 638nm, 589nm, 532nm, 445nm and 405nm together using dichroic filters.

How to:
Two lasers are placed perpendicular to each other. Where the beams meet a dichroic filter is placed so that one beam passes through the filter and one gets reflected at 90° into the other beam.

Diagram:

Picture:

Can combine multiple beams with different wavelengths.

Cannot be used to combine the same wavelength.

Polarized Beam Splitter

Common use:
Combining two lasers of the same wavelength once.

Description:
Polarized beam splitters take two beams of opposite polarization and combines them together. This can only be done once; if the output of one PBS cube is shone into another it will split the beam.

How to:
Two lasers are placed perpendicular to each other. Once module will be rotated 90° so that the lasers are oppositely polarized. Where the beams meet a polarized beam splitter is placed so that one beam passes through the cube and one gets reflected at 90° into the other beam.

Diagram:

Picture:

Can combine two beams of the same wavelength with minimal losses

Cannot be used to combine more than two beams of the same wavelength.

Other notes:
With multi mode diode lasers one will have to be rotated 90° so that the beams are like this - and | when they get combined it will give you this beam + To avoid this you can use a 1/2 wave plate. This changes the polarization, but not the orientation of the beam so that both beams will be set up like this | and | giving you one | beam.

Polarized beam splitters can be used with knife edging to combine two sets of knife edged beams.

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#### bennett326

##### Well-known member
Re: Tutorial: How to combine lasers

good informational thread id rep you if i could. thanks for having the patience to make these types of threads :beer:

that last picture is a module andy made right? fcking crazy imaging that in your scanner

#### ARG

##### Well-known member
Re: Tutorial: How to combine lasers

good informational thread id rep you if i could. thanks for having the patience to make these types of threads :beer:

that last picture is a module andy made right? fcking crazy imaging that in your scanner

Thanks! :beer:

I borrowed the knife edging picture and the last one from andy. That last one is 10W :eg: Would be amazing in a projector, but I would be to afraid of it. 4.4W burned enough holes in my cloths/walls/table/chair as is

Imagine having this projector:

Dual Green, 10 445nm diodes and 48 red diodes

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#### bennett326

##### Well-known member
Re: Tutorial: How to combine lasers

Thanks! :beer:

I borrowed the knife edging picture and the last one from andy. That last one is 10W :eg: Would be amazing in a projector, but I would be to afraid of it. 4.4W burned enough holes in my cloths/walls/table/chair as is

Imagine having this projector:

Dual Green, 10 445nm diodes and 48 red diodes

yeah i saw that on his site and hell yeah that would be incredible and a pair of C.Ts :drool: whats your guess on price just for fun (w/o scanners) as is in the picture im thinking \$22k easily more depending on what brand of green hes using etc. also imagine the time spent aligning those 48 reds :tinfoil:

#### grainde

##### Well-known member
Re: Tutorial: How to combine lasers

Cool thanks for sharing! Ive been thinking about a multiwavelength build for a while now...this will be very useful! :beer: and +1 if I can...

#### Blord

##### New member
Re: Tutorial: How to combine lasers

Thanks for the explanation with schematics. It is very clear now ! :gj:

#### lasersbee

##### Well-known member
Re: Tutorial: How to combine lasers

Thanks for posting this informative beam combining Thread...:gj:

Jerry

You can contact us at any time on our Website: J.BAUER Electronics

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#### Arayan

##### Well-known member
Re: Tutorial: How to combine lasers

WOW, very interesting... thanks Alex :beer:

#### Kizdawg

##### New member
Re: Tutorial: How to combine lasers

You answered alot of my Q with just 1 post.. Nice.

#### ARG

##### Well-known member
Re: Tutorial: How to combine lasers

#### Laser Smith

##### Active member
Re: Tutorial: How to combine lasers

I vote sticky, and I'm surprised I'm the first

#### Kizdawg

##### New member
Re: Tutorial: How to combine lasers

So where would you suggest I look for cubes and parts.. Ebay is so vague when you dont really know what you are looking for. and should I be looking for the largest cube I can fit in my build or does size matter? lol Also 1/2 wave plate kinda buggs my brain.. does it actually change the way the light waves so that it can be combined by the PBS? I origionally would have thaught that just rotating the module would have got rid of the + effect. I need to read more on all this..

I burned a hole in my celing last night ooops.. Also how do these work with single mode diodes? do you still end up with a single mode or is it more like a multi? And can you correct the beam after combining to get something better? like the Dr Lava correction optics?

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#### Fiddy

##### Well-known member
Re: Tutorial: How to combine lasers

holly shit! I love tutorials of this magnitude! :gj:

#### ARG

##### Well-known member
Re: Tutorial: How to combine lasers

So where would you suggest I look for cubes and parts.. Ebay is so vague when you dont really know what you are looking for. and should I be looking for the largest cube I can fit in my build or does size matter? lol Also 1/2 wave plate kinda buggs my brain.. does it actually change the way the light waves so that it can be combined by the PBS? I origionally would have thaught that just rotating the module would have got rid of the + effect. I need to read more on all this..

Ebay generally isn't the best place to buy these kinds of things, unless they have a part number from Edmund or Thorlabs so you can see if it's what you need. Lots of projector supplies places sell these.
PBS Cubes and kits
Waveplates and anamorphic prisms
Lasershow Parts

Size does not matter for the cube, as long as it's big enough to fit your beams on. You need to pay attention and make sure it's coated for the wavelength you are using it for, and that it's a good glass type. (Don't use SF-11 for 445nm, use BK-7)

The Stanwax ones are really good, the transmissions are really high. The customer support there is also superb.
The 1/2 wave plate just polarizes the beam, it has the same effect as turning the module 90 degrees, but without changing the light orientation.
If you rotate the module (without a polarization plate) to | and | both beams will go straight through the cube.

You can get a cheap cube from surplus shed to muck around with, I don't know where to get a cheap wave plate though. Lots of diode sleds also have tiny cubes that you can use.

holly shit! I love tutorials of this magnitude! :gj:
I vote sticky, and I'm surprised I'm the first

Thanks!

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