Calculating Laser Power Absorption: 800 nm, 20 W, 0.25 cm Layer

In summary, the remaining power behind the goblet is 16.8 W and the layer thickness of the water needs to be 0.615 cm to achieve 99% absorption.
  • #1
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Hi,I need help with this question

Assume you have a laser emitting a wavelength of 800 nm with power 20 W. You irradiate a goblet filled with water whose layer is 0.25 cm thick.
The absorption coefficient of water at this wavelength is 0.65 cm-1.
a) What is the remaining power behind the goblet?
b) How large should the layer thickness of the water be, if you desire only 1% of the incident power behind the goblet? (equals 99% absorption in the water)
Note:You can neglect the reflection losses and all absorption losses in the walls of the goblet.

I am not really sure how to start.
 
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  • #2
Could you please help me?a) The remaining power behind the goblet is 16.8 W. This is calculated by multiplying the incident power (20 W) by the transmission coefficient, which is equal to 1 - (absorption coefficient x thickness of the layer). Therefore, the transmission coefficient is equal to 0.85 (1 - 0.65 x 0.25) and the remaining power is 20 W x 0.85 = 16.8 W.b) To get 99% absorption in the water, we need to calculate the thickness of the layer required to achieve this. The absorption coefficient remains the same (0.65 cm-1), so we can use the same formula as before, but solving for the layer thickness. The layer thickness required is 0.615 cm. This is calculated by dividing the desired transmission coefficient (1 - 0.99 = 0.01) by the absorption coefficient (0.65 cm-1), giving 0.01 / 0.65 = 0.615 cm.
 

1. How is laser power absorption calculated?

To calculate laser power absorption, you need to know the laser power (in watts), the wavelength of the laser (in nanometers), and the thickness of the layer (in centimeters). You also need to know the absorption coefficient, which is a material-specific value that describes how much of the laser's energy is absorbed by the material.

2. What is the absorption coefficient?

The absorption coefficient is a material-specific value that describes how much of the laser's energy is absorbed by the material. It is typically represented by the symbol α and is measured in units of inverse length (e.g. cm-1). It takes into account factors such as the material's optical properties and the laser's wavelength.

3. How does wavelength affect laser power absorption?

The wavelength of the laser is an important factor in calculating power absorption because different materials have different absorption coefficients at different wavelengths. This means that the same laser power may be absorbed differently by different materials, depending on the laser's wavelength.

4. What is the equation for calculating laser power absorption?

The equation for calculating laser power absorption is Pabs = P0 * (1 - e-α*d), where Pabs is the absorbed power, P0 is the incident power, α is the absorption coefficient, and d is the thickness of the material layer.

5. Can laser power absorption be increased?

Yes, there are ways to increase laser power absorption, such as using materials with higher absorption coefficients or reducing the thickness of the material layer. Additionally, factors such as the laser's intensity and beam profile can also affect absorption. However, it is important to consider any potential safety hazards when increasing laser power absorption.

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