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Name: Alexander W
Status: student
Age: 17
Location: N/A
Country: N/A
Date: 1999 

Can a Laser stron enought to cut paper, yet have a controlable lenght? By controlable lenght I mean that the lasers energy is limited to a certain area, and that it will not exceed that area, yet, be strong enouth to cut paper in any part of that area? Is this posible to archive this without using mirrors for deflecting the laser? How big and coslty would it be to make such a device? Please answer, im trying o do sucha device for my Physics proyect.

You could limit the range within which a laser beam is intense enough to cut paper by beginning with a wide beam and focusing it with a short-focal-length lens. The intensity in the focal spot will be much greater than it is away from the focal spot. Such a laser would be intense enough to blind you even well away from the focal spot. I don't know how much it would cost.

Tim Mooney


You can use a laser to cut metals. This is done routinely. Because a laser beam's power per unit area (referred to as heat flux) can be very high, you can use a pulsed laser to cut almost instantly by ablating the metal. The fact the you can RAPIDLY raise the temperature of the metal to its melting point (before heat starts to spread to other parts of the item being cut) makes it possible to make clean and clear cuts (in many metals). I am sure you can cut paper too but I do not know off hand what laser power should be used. The problem I see is that the paper may catch fire. Most metals melt or evaporate without being ignited. Paper (and a host of other materials) are different in that once they reach a temperature (called the ignition temperature), they catch fire. If you do this entire operation in a CO2 environment, the fire could be self-limiting.

Lasers which have sufficient power to cut metals are rather dangerous to work with and users must receive safety and operating courses to handle lasers. Even small amount of laser reflected from the metal being cut can blind a person. In any case, you may want to get a basic book on lasers from your library and review it first.

If you prefer a safe thermal method of cutting paper, I suggest the use a magnifying glass with sun rays (or a light source). You can actually make a lens made of ice (which nevertheless focuses the incoming beam). You can also use a hot wire (by applying electricity from a battery across a suitable metal wire) to cut a piece of paper. In these cases, you need to be aware that the paper will catch fire and thus, safety should be the priority # 1 in the planning and conducting the demonstration. You should discuss the project with your teacher(s) for guidance and advice before spending time and effort on it.

Good luck.

Dr. Ali Khounsary
Advanced Photon Source
Argonne National Laboratory

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