# Build a laser capable of cuting intricate designs out of thin metal

1. Nov 13, 2003

### wolram

would it be to expensive to build a laser capable of cuting
intricate designs out of thin metal or wood about 0.5mm?
for a hobby project.

2. Nov 13, 2003

### NateTG

Technically that depends on what you mean by expensive, but the answer is probably yes.

I would be surprised if it cost less than $1000. 3. Nov 13, 2003 ### Njorl You might be able to use bundled diode lasers to cut wood, but I don't know about metal. I have only heard of metal being cut with CO2 lasers. You'd spend a few thousand on the optics, the tube and electronics for that. It is usually thick steel being cut though, so maybe there is something less expensive for cutting thin metal. The economic advantage of laser cutting comes in when you make enormous numbers of identical, machine controlled cuts. I don't think that comes into play in a hobby. Njorl 4. Nov 13, 2003 ### wolram thanks anyway, i cant aford$1000 but it was worth asking.

5. Nov 13, 2003

### Ambitwistor

There is the \$10,000 VersaLaser which can cut intricate designs into "paper, wood, a variety of plastics, leather, some coated metals, and even stone and marble".

http://www.pcmag.com/article2/0,4149,1360231,00.asp

6. Jan 17, 2004

### Sammywu

I always have a question about laser when reading from a common book descrbing how laser works. Most of books said that first you excited some electrons of those atom by some electricity, the elctrons will emit a certain frequency of the photons, the photons will be bounced back and forth within the mirrors and hot other electrons and these electrons will release more photons with the same frequency and the photons will be built up like chain reaction.

This does not make sense. Where does this chain reaction come from? There has to be energy to build up these photons. The way it describes seems to there will be created energy through this resonance of the light. Totally violating the conservation of energy.

Do any one have answers for that? Did I misread these books?

7. Jan 17, 2004

### NateTG

Actually, what you describe is a 'tricky' or complicated part of a laser.

This is a simplified explanation, but it's AFAIK reasonably close to current theory. Hopefully it clarifies the issue.

Electrons can only be in certain 'orbitals' on atoms and molecules. Whenever an emission occurs, an electron goes from a higher state, to a lower state orbital. (You've probably already seen this part.)

Now, in order to use this as an amplifier, you need to create a situation where most atoms are on the higher state instead of the lower one.

A classical method for doing this is to find an atom that has three states, a ground state, a high state, and a low state, where transitions from the low state to the ground state are relatively infrequent.

Then use an electric field to get the electrons into the high state. The electrons naturaly go to the low state. This can create a metastable situation where the electrons can be triggered.

The electrons can be exited to the higher state by using other energy sources like flash lamps as well.

8. Jan 18, 2004

### UltraPi1

Google CNC plasma cutters.

9. Jan 18, 2004

### Sammywu

Natetg,

Thank you for your reply. Still have question. Which state of the three is the lowest, the ground or the low?

Also, my question is regarding the energy conservation. If I added total energy E into this system by whatever means, I can only created as many photons of E/hf.

How come there seem to be more photons generated than this formula based on these books?

10. Jan 18, 2004

### NateTG

Laser amplification takes energy from the low->ground transition. It's a cycle:
Ground->High->Low->Ground.

Tube lasers are extremely inefficient, I think it's somewhere around 16% for the best ones.

LED lasers are IIRC in the mid to high double digits for efficiency. (But I don't know how they work.)

I've never seen any indication that lasers violate conservation of energy. If you can cite a specific passage I might be able to help you.

11. Jan 19, 2004

### Sammywu

NateTeg,

In this Dk ( Dorling Kindersley, Inc ) published EYEWITNESS SCIENCE, LIGHT. There is a section LASER LIGHT. It stated, " When light from one atom strikes its neighbors more light is released, and this all at the same time."

This implys with one photon striking the other atoms, there will be multiple photons generated. This violates Energy conservation.

Is this statment just ballony?

That is a book I bought for my kids. Hopefully intriguing their interests to modern Physics.

12. Jan 19, 2004

### chroot

Staff Emeritus
No, it doesn't. First, the lasing medium must be "pumped," by being strobed with a special frequency of light, or by having a current passed through it, or by some other mechanism. The point of "pumping" is to create a population inversion, in which many of the atoms in the medium are in an excited, metastable state.

Then, when one atom releases a photon characteristic of the decay of that excited state, the photon stimulates other atoms to produce coherent photons -- and so on, creating a chain reaction.

The stimulated emission of radiation does not violate energy conservation, because, before it can happen, something must have pumped the lasing medium to create the necessary population inversion. Different lasers use different techniques to achieve this population inversion, but it is a necessary step for all lasers.

- Warren

13. Jan 19, 2004

### NateTG

In order for the second atom to emit two photons it must be exited. (For example in the 'low' state that I described.)

14. Jan 19, 2004

### Nereid

Staff Emeritus
To be redundant, the energy which is deposited in the metal/paper/wood/etc being cut is < the energy in the laser beam. The laser beam's energy, in turn, is < the energy supplied to the laser to make it lase in the first place.

The principal reason for using lasers to cut or burn things isn't energy efficiency (per se); it's things like precision, control, accuracy, ease of use, ...

BTW, did you know that the basic mechanism at work in a laser is the same as in a maser? And that maser clocks are among the most accurate? Also, that there are giant 'water-masers' in the sky (in gas clouds around nascent stars)?

15. Jan 20, 2004

### Sammywu

Thank you for all your help. This definitely cleared a question that I had when I found I can't explain to my kids where these energy could possibly come from.

I don't know about maser. What is a maser?

16. Jan 20, 2004

### Nereid

Staff Emeritus
laser = light amplification by stimulated emission of radiation (or similar)
maser = same, 'microwave' -> 'light'

Masers were the first off the drawing board into the lab; then into commercial production. As a term in general use, 'atomic clock' is imprecise; IIRC, in its early usage it meant a 'hydrogen maser', and maybe still does. They are still widely used as clocks, for their combination of transportability and stability, even though they are no longer the best clocks.

17. Jan 20, 2004

### Sammywu

Neried, Thanks. Why is there giant water masers in the gases near nascent stars?

18. Jan 20, 2004

### Nereid

Staff Emeritus
Right time; right place. A gas in which a population inversion can be fairly easily created. An energy source which can pump the inversion. AFAIK, no need for 'mirrors', they're one-pass masers.