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

• A
• jgk5141
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.

#### jgk5141

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.

Draw a diagram that shows the flow of energy from the laser to all the thermal and chemical products.

• Twigg and jgk5141
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?

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.

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.

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?

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. How do you calculate the temperature change of a laser-irradiated material?

The temperature change of a laser-irradiated material can be calculated using the following formula: ΔT = P/AρC, where ΔT is the temperature change, P is the laser power, A is the area of the material, ρ is the material density, and C is the material's specific heat capacity.

## 2. What units should be used in the calculation?

The units used in the calculation should be consistent. Laser power is typically measured in watts (W), area in square meters (m²), density in kilograms per cubic meter (kg/m³), and specific heat capacity in joules per kilogram Kelvin (J/kgK).

## 3. What factors can affect the accuracy of the temperature change calculation?

Several factors can affect the accuracy of the temperature change calculation, including the laser's wavelength and intensity, the material's reflectivity and thermal properties, and the environment's ambient temperature and pressure.

## 4. Is there a specific formula for different materials?

Yes, the formula for calculating the temperature change of a laser-irradiated material may vary depending on the material's properties. For example, the specific heat capacity of different materials may differ, requiring a different value in the calculation.

## 5. Can the temperature change be accurately predicted using this formula?

The formula for calculating the temperature change of a laser-irradiated material provides a good estimate but may not account for all variables. Other factors, such as heat dissipation and thermal conductivity, may also play a role in the actual temperature change. It is best to use this formula as a guide and conduct experiments to determine the precise temperature change.