# Calculating the heating effect of a Class IV laser

1. Jul 5, 2010

### alex111888

Hi guys,

I am of a Mechanical Engineering background, however my dissertation has a largely optics based focus, and I am struggling with understanding the heating effect of a Laser.

I will be using various wavelength ND:Yag lasers, and will be focussing them onto a target material, which I have not yet decided upon. I need to be able to calculate the heating effect of the laser on this material.

For example, if I pulse the laser constantly for 2 seconds, what will be the temperature increase of the material?

For arguement's sake, we could consider the laser to be of these specifications:

Dimensions
Laser transmitter 325 x 201 x 119 mm
Laser receiver 105 x 77 x 23 mm
Mass
Laser transmitter < 7.5 kg
Laser receiver < 0.5 kg
Aperture
10 mm
Beam Divergence
Tactical @ 1.06 μm < 1 mRad
Output Energy
< 300 mJ @ 1.06 μm
< 90 mJ @ 1.57 μm
Repetition Rate
20 Hz (on both wavelengths)
Average Power
< 325 W

Thank you very much for your input.

Alex

2. Jul 5, 2010

### Andy Resnick

The temperature increase will be driven by the amount of absorbed energy, nothing more- unless the pulse is of ~fs duration.

3. Jul 6, 2010

### alex111888

thank you for your reply. I am ultimately looking for the surface temperature within the beam of the laser. As surely the part inside the beam will become much hotter than that outside? also- do you have any kind of equations that would be appropriate?