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Multiple laser diodes?

Posted by LarsK 
Multiple laser diodes?
April 16, 2015 08:02PM
Hello all,

I have been thinking about several laser diodes. I am working from the Nichia NDB7875-E with a 4.01 focus convex-flat lens. Lens diameter is 6.33mm.

It looked really simple when I started but I can't figure it out. I modelled it in SW to have a look.

So I start with two lasers:

This is OK. You can see the lens support are just touching each other. In this setup I respect that both lasers hits the same point at exact 4.01 mm.

I then try to fit in another and thats where it stops:

So I have been thinking about buying lenses with 9mm focal length instead ( [www.aliexpress.com] )

This would allow me to make a setup like this (6 lasers):

They would hit at 42.3 deg.

Each laser is 65 USD and lenses 5 usd a piece. That is 420 USD for a total nominal effect of 1.6 * 6 = 9.6W or 12W if running each at peak 2W. Then comes the cost of the water cooling.

I have looked at buying lower power lasers for bundling them. But the 65 USD for 1.6W is actually the better deal. The new 3W is crazy expensive.

At US 85$ I can get a CO2 tube that will blast 40W.

Is there any future to coupling diode lasers like this, or is the only justification in diodes that if you need just ~1W then it is much more convenient then having to deal with the big tubes and power and what not?
Re: Multiple laser diodes?
April 17, 2015 03:08AM
... the positioning of the focus related to diode housing and lens position isn't uniform, but off some 10 to 100 microns -- so you'll need some methode of adjusting them.

This is mostly done with a 2-axis flex-holder with adjusting screws -- so the distance of diodes in a multi-diode setup is mostly some centimeters and the beams are combined by PBS cubes, waveplates or knife-edge-mirroring them together ... look at the common high wattage diode-modules for show-lasers ...

Aufruf zum Projekt "Müll-freie Meere" - [reprap.org]
Call for the project "garbage-free seas" - [reprap.org]
Re: Multiple laser diodes?
April 17, 2015 10:49AM
Hello Viktor,

I have now looked more at combining lasers with prisms and what. I looked at:


Which gives a fairly good explanation in my opinion.

- One PBS cube is starting at 40 USD ( [www.aliexpress.com] ) and that would allow combining just two lasers.

I guess for just 6 lasers I could do knife edging (~5 usd per mirror but only one focal needed so almost same balance). The advantage of knife edging is that the lasers would hit at 90 deg and not 43 deg as in mine. I think that is a big advantage (?).

In the end what keeps me from ordering is the cost - It makes sense that for scene lighting or science you want to pay a lot for RGB type lasers. But for laser cutting - Is there really any big advantage to having a blue laser instead of a CO2 tube?

Again - We are talking at least 460 USD for the basic setup with 9.6W power - And then comes electronics, power supply etc.

A 90W CO2 would cost 241 USD ( [www.aliexpress.com] ) and 160 USD for the power supply.

That is almost 10x the power for the same price.

Is there any advantage to blue lasers that justify this and makes it worth continuing with combining lasers?
Re: Multiple laser diodes?
April 17, 2015 05:45PM
... cheap CO2-lasers+focussing lens will burn/engrave a line maybe 0.3mm wide ... a 445nm-diode with a standard collimator and short focal distance (e.g. 30mm) is good enough for 0.05mm.

Combining several diodes will result again in 'thicker' lines as you have to rise the focal distances and/or average the single focusses to a bigger shape.

With my 6x 445nm-diode head I'm receiving focus diameters of 0.3mm in 60mm distance, but could be as good as 0.2mm in 40mm ... but then it's more meant for sintering or surface treatment, not for engraving or cutting ...

Aufruf zum Projekt "Müll-freie Meere" - [reprap.org]
Call for the project "garbage-free seas" - [reprap.org]
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