Is this statement  true about a burning laser

For your information, when it comes to the ability of a laser to burn it isn't the total output power that makes this possible but the intensity of the beam falling on an object. A lower power pointer producing a smaller spot size can be as effective as a more powerful laser which produces a larger diameter spot size. The intensity is given by the output power in the beam divided by the area of the spot. If the spot is circular in shape then the intensity is inversely proportional to the square of the radius of the spot. So if the radius of the spot size is halved then the intensity increases by a factor of 4.THANKS

Re: Can some one tell me if this statement is true

Well I guess it is true, take a 100mW laser and a 200mW, the 200mW dot is 1 cm wide and the 100mW is 1/3 mm wide. It's obvious the 100mW will be a better burner, but I'm not so sure the last centence is true, basicaly it's saying if you have a laser with a 1/2 cm wide dot, and then collimate it to 1/4 cm the laser will burn 4x better then when it was 1/2. I don't know, but I'm sure more experienced people will have better answers than this one. ;D

Re: Is this statement  true about a burning laser

interesting question... :-?

Re: Is this statement  true about a burning laser

It's actually half true. The key to the answer is in the thermal conductivity of the object you try to burn.

In a practical situation like burning a piece of paper, it will be mostly the power density that matters. 100 mW on 5mm2 would work just as wel as 200 or 10 mm2.

But lets say you were trying to cut through a sheet of (blackened) aluminium with a 200 mW laser. There is no way that will succeed since the aluminium just conducts away any energy from the spot, no matter how small you make it.

In practical situation this is overcome by using a pulsed laser, heating up the material so quickly it cannot conduct the heat away fast enough resulting in local melting or ablation.

Re: Is this statement  true about a burning laser

It's true that the "burning power" is inversely proportional to the dot surface (or the square of the radius).But the "beam intensity" (I think "irradiance" is the corect term to use here) is not the only thing that makes a burning laser possible.Like Benm said, the thermal conductivity and the material's ability to absorb energy(light at the given wavelength) rather than reflecting or passing it play a crucial role too.