Medical Laser
Separate optical power, energy, exposure time, and circular beam area in an ideal homogeneous-beam model.
Operating mode
Beam inputs
Why these controls?
Diameter sets the beam area A = πr²; power and time (or pulse energy and duration) set the energy. Move them to see how the same energy spread over a larger area lowers irradiance and fluence.
Calculated distribution
Homogeneous circular beam
Beam area
0.503 cm²
Total energy
10.000 J
Average irradiance
9.947 W/cm²
Energy density (fluence)
19.894 J/cm²
Exposure
2.0 s
Diameter: 8.0 mm → radius: d/2 = 4.00 mm
Unit conversion: 4.00 mm ÷ 10 = 0.400 cm
Area: A = πr² = π × (0.400 cm)² = 0.503 cm²
Energy: E = Pt = 5.0 W × 2.0 s = 10.000 J
Spatial distribution
Same energy, different diameter
Color represents relative calculated fluence only. It is not a tissue temperature, damage, depth, or clinical effectiveness map.
Diameter response
Fluence vs. beam diameter
Model equations
I = P/A W/cm²
H = E/A J/cm²
E = Pt continuous beam
Student checks
- Double diameter and confirm that area becomes four times larger.
- At fixed energy, confirm that doubled diameter reduces fluence to one quarter.
- In pulse mode, keep energy fixed and change duration: fluence stays constant while average power changes.
- Investigate why homogeneous and Gaussian beam profiles differ in real lasers.