Why are some beams rectangular, some circular?

[EpicHam]

Hey , there .
I just got myself a 445nm laser and I just realized the beam output is rectangular.

After a bit of googling , it happens that is called multi-mode laser diode.
And one of its characteristic is a rectangular beam output , or so I read.

However, this got me thinking.
How come we can't make a multi-mode laser diode that can have a circular laser beam output?

For one ,the divergence would be better . (or so I read )
For two , as a result, it would make a much better burning and also much more far reaching.


PS: I'm as green as a leprechaun with regards to laser... so.... if this is a stupid question... don't cave my skull in eh?

 

[scumbagatheist]

You're dealing with the differences between single-mode and multi-mode diodes.

Typically, 445nm lasers will have either G-series lenses for best output power, or a glass, 3 element lens for a better dot, but less power.

If you want a powerful burner, you're going to be stuck with a multi-mode diode. If you want the prettiest blue dot, you could go for a single-mode PL450 diode. It's far less power, but a very pretty, tight beam like and single-mode red or green.

 

[EpicHam]

You're dealing with the differences between single-mode and multi-mode diodes.

Typically, 445nm lasers will have either G-series lenses for best output power, or a glass, 3 element lens for a better dot, but less power.

If you want a powerful burner, you're going to be stuck with a multi-mode diode. If you want the prettiest blue dot, you could go for a single-mode PL450 diode. It's far less power, but a very pretty, tight beam like and single-mode red or green.

but it'll be a short distance burner due to the poor divergence of multimode diodes tho.

What if I want a LOOONG distance burner ..
And more importantly , what is multi-mode?
Correct me if I'm wrong , does that mean laser diode consisting of different wavelength being streamed into a single beam?

 

[scumbagatheist]

My 3W 445 burns plywood at 3 meters. How powerfully do you want to burn?

The "modes" refer to the way the diode is built. To put it in overly-simplified terms, think of it like stacked lights. A single-mode makes n amount of photons. To get a higher output, manufacturers are basically stacking "modes". It's much more complicated than this, but you get the idea.

I wonder what kind of burning you want to do, as you don't seem to care about how nice your beam "looks". Why is it so important to have a powerful burner? Why not just buy a 10W CO2 laser?

 

[EpicHam]

My 3W 445 burns plywood at 3 meters. How powerfully do you want to burn?

The "modes" refer to the way the diode is built. To put it in overly-simplified terms, think of it like stacked lights. A single-mode makes n amount of photons. To get a higher output, manufacturers are basically stacking "modes". It's much more complicated than this, but you get the idea.

I wonder what kind of burning you want to do, as you don't seem to care about how nice your beam "looks". Why is it so important to have a powerful burner? Why not just buy a 10W CO2 laser?

I still don't quite get it about the mode stuff.

So does that mean that magnified , multi-mode lasers would look something like this?

if so.. why does multi-mode have to be rectangular?
I mean... what does the lens have to do with whether the beam is rectangular or what? Its just there to focus and collimate right?

As for the distance thing.
well maybe around 20m to 40m away would be awesome.
Now why not a CO2 laser?
Because you can't see the beam. Which chops its COOL FACTOR and makes it very dangerous for both people around and myself.

 

[scumbagatheist]

No....

First of all, you have no business burning things at those distances. Secondly, no current handheld is going to give you that kind of power. Lastly, IF there was a diode that gave that kind of output, it would necessarily be multi-mode.

The "mode" has nothing to do with wavelength. It's about the way the lasing materials are arranged, the shape and type of cavity, etc.

Why don't you just use your search bar and do more reading. You'll pick it up without having to be spoonfed the answers.

 

[daguin]

The shape of the beam is affected by the shape of the crystal

One of the ways to get more power from a diode is to increase the size of the point of emission or to give it several points

You have to realize that, for the most part, the industry (the people paying the bills) are NOT concerned with pretty round beams, at a distance, like us

In industry the laser light is utilized within inches of the emission point

Peace,
dave

 

[norbyx]

As for the lasers you have in the picture that is a rgb setting, those are 3 lasers that combined through mirrors and prisms form one single beam of a different color (in this case white).
Now why would you want to burn something 40 meters away? That seems like odd to me. Remembers that this aren't toys and if you cause any type of damage with a laser you might get into real trouble, and this forum doesn't like trouble makers.

 

[EpicHam]

As for the lasers you have in the picture that is a rgb setting, those are 3 lasers that combined through mirrors and prisms form one single beam of a different color (in this case white).
Now why would you want to burn something 40 meters away? That seems like odd to me. Remembers that this aren't toys and if you cause any type of damage with a laser you might get into real trouble, and this forum doesn't like trouble makers.

To impress my friends .
We were testing the laser's ability and we found that a 1W is pretty much out of juice as soon as we go over 20-ish m.
Just playing around thats all.

As the the multimode config , I just digged out a little article for it.
Which I am in the progress of banging it against my head .
(yes, we wore goggles. Yes , there were no one around on the beach.)