How to calculate the temperature change of a laser-irradiated material

In summary: From there, you can use the known optical absorption, reflection, and transmission data, along with the source parameters of your laser system, to approximate the temperature change of your sample. Keep in mind that you will need to make some assumptions and approximations about thermal relaxation times and absorption mechanisms. Additionally, you will need to take into account the fact that all absorbed energy is converted to thermal energy.
  • #1
jgk5141
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TL;DR Summary
How to calculate the temperature change of a laser-irradiated material when the absorption, laser pulse energy, spot size, wavelength, pulse width, and frequency are known?
I am looking to approximately calculate the temperature change of a sample that was exposed to a laser pulse. Experimentally, we know the optical absorption, reflection, and transmission, as well as the source parameters for our laser system. I realize that I will have to make approximations about the thermal relaxation times, optical absorption mechanisms, and the fact that the absorbed energy is completely converted to thermal energy. I am simply trying to understand absolute thermal maximums from the sample from the laser exposure.
 
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  • #2
Draw a diagram that shows the flow of energy from the laser to all the thermal and chemical products.
 
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Likes Twigg and jgk5141
  • #3
Are you really referring to a pulse, or are you referring to a laser beam that is suddenly turned on and then allowed to continue irradiating the sample?
 
  • #4
Chestermiller said:
Are you really referring to a pulse, or are you referring to a laser beam that is suddenly turned on and then allowed to continue irradiating the sample?
Yes, I am really referring to a pulse. The laser pulse width is ~6ns from the experiment.
 
  • #5
With a 6ns pulse width, you will be dumping a ludicrous amount of peak power into the target sample. Depending on the absorbance, you may see ablation of the target. To calculate the temperature change of the target (as per the original post), you will need to factor in the latent heat due to ablation.

Overall, the advice from @Baluncore in post #2 still applies.
 
  • #6
Twigg said:
With a 6ns pulse width, you will be dumping a ludicrous amount of peak power into the target sample. Depending on the absorbance, you may see ablation of the target. To calculate the temperature change of the target (as per the original post), you will need to factor in the latent heat due to ablation.

Overall, the advice from @Baluncore in post #2 still applies.
This makes sense. Could you point me in the direction to get started with this?
 
  • #7
As in post #2, start by drawing a diagram that shows the flow into your sample from the laser, as well as the flow of power out of your system due to ablation and any other losses (conduction, etc.).
 

1. What is the equation for calculating the temperature change of a laser-irradiated material?

The equation for calculating the temperature change of a laser-irradiated material is Q = mcΔT, where Q is the heat absorbed by the material, m is the mass of the material, c is the specific heat capacity of the material, and ΔT is the change in temperature.

2. How do you determine the heat absorbed by the material?

The heat absorbed by the material can be determined by measuring the energy of the laser beam and the absorption coefficient of the material. The absorption coefficient can be found in literature or can be experimentally determined.

3. What is the specific heat capacity of a material?

The specific heat capacity of a material is the amount of heat required to raise the temperature of one unit mass of the material by one degree Celsius. It is usually measured in joules per gram per degree Celsius (J/g°C).

4. How does the laser power affect the temperature change of the material?

The laser power directly affects the temperature change of the material. The higher the laser power, the more energy is absorbed by the material, resulting in a greater temperature change. However, the specific heat capacity of the material also plays a role in determining the temperature change.

5. Can the temperature change of a laser-irradiated material be accurately predicted?

The temperature change of a laser-irradiated material can be accurately predicted if all the necessary parameters, such as laser power, absorption coefficient, and specific heat capacity, are known and accounted for in the calculation. However, there may be some variations due to factors such as heat dissipation and surface reflection. It is important to conduct experiments to validate the predicted temperature change.

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