Multiple cube beam combiner "it can be done"..... Has anyone seen this article?

[Alaskan]

Multiple cube beam combiner "it can be done"..... Has anyone seen this article?

A couple years ago I came across a post or article about laser beam combining using multiple beam splitter/combiner cubes. The article had a title of "It can be done..." but I don't remember the full title. The design used several cubes, they probably weren't polarized cubes or perhaps were but used waveplates to rotate the polarities and admittedly, had more loss than other methods of combining beams, but I'm interested in finding the information again. If anyone has seen this information somewhere please post or PM me where.

I've tried searching through google for a couple of hours and still can't find it.

Thanks!

Chris

 

[KrowBar]

Re: Multiple cube beam combiner "it can be done"..... Has anyone seen this article?

I have been unable to locate the original post or article you are referring to. PBS cubes can only combine 2 beams. It is possible with very tight control of polarity, and amplitude to combine phase controlled mutually coherent beams (imagine here the reverse of the "star effect" diffraction grating), but this proves quite difficult even in tightly controlled lab environments. However, you can also combine beams using dichroic mirrors or prisms if the beams are different wavelengths. You can imagine a prism working in reverse where beams of different wavelengths are incident at the appropriate angle for the particular color and all exit at the same angle in a combined broad spectrum (white) beam. This is much less sensitive to misalignment issues and doesn't require mutual coherence of the beams. if you want to do some deathstar beam combination stuff, then the best bet is to split a single beam and run it through some kind of doped fiber optical amplifier system and then recombine the amplified beams.

 

[diachi]

Re: Multiple cube beam combiner "it can be done"..... Has anyone seen this article?

However, you can also combine beams using dichroic mirrors or prisms if the beams are different wavelengths. You can imagine a prism working in reverse where beams of different wavelengths are incident at the appropriate angle for the particular color and all exit at the same angle in a combined broad spectrum (white) beam.

Planters has a good video on this - he combined several red diodes using a prism. Each diode was individually temperature controlled to adjust the wavelength IIRC.

 

[Benm]

Re: Multiple cube beam combiner "it can be done"..... Has anyone seen this article?

As long as the wavelengths are different there are plenty of options of (at least) theoretically combining the beams from many lasers.

With equal wavelengths the only 'real' way is PBS combining a maximum of two, and the rest would be knife-edging or other 'not truly combining' approaches.

Perhaps it's somehow possible to combine by converting to circular polarisation and back. Another approach could be phase shifting and combining, as can be done with RF signals. I'm not sure this could practially be done though as the lasers would have to be wavelength-locked to eachoter with variable phase shift.

 

[Alaskan]

Re: Multiple cube beam combiner "it can be done"..... Has anyone seen this article?

Thank you, I'm going to keep an eye out for methods to coaxially combine more than two beams of the same color, so far, I haven't found it. I am also interested in using a prism to combine several colors to make white, hoping that method will allow close to a coaxial combined beam. The "it can be done" article about using cubes I'm looking for was most likely non-polaraized dichro cubes.

 

[mk64n]

Re: Multiple cube beam combiner "it can be done"..... Has anyone seen this article?

the best bet is to split a single beam and run it through some kind of doped fiber optical amplifier system and then recombine the amplified beams.

Are we talking 4 digit number cost here?