Laser Beam Spot Size Calculator
Calculate the focused spot size and depth of focus for laser beams with precision
Calculate Laser Beam Spot Size
Wavelength of the laser light
Diameter of the laser beam hitting the lens
Focal length of the focusing lens
M² = 1 for ideal Gaussian beam, higher values for real beams
Laser Beam Focus Results
Spot Size at Focus
Depth of Focus
Formula used: S = (4 × M² × λ × f) / (π × d)
Depth of Focus: DOF = 2 × π × (S/2)² / (M² × λ)
Spot Size Analysis
Example Calculation
Green Laser Pointer Example
Wavelength (λ): 532 nm (green laser)
Beam diameter at lens (d): 0.5 mm
Focal length (f): 50 mm
Beam quality (M²): 1.12 (slightly non-ideal)
Calculation Steps
S = (4 × M² × λ × f) / (π × d)
S = (4 × 1.12² × 532×10⁻⁹ × 0.05) / (π × 0.0005)
S = (4 × 1.2544 × 532×10⁻⁹ × 0.05) / (1.5708×10⁻³)
S ≈ 85.2 μm
DOF ≈ 67.97 mm
Laser Properties
Wavelength
Determines diffraction limit
Shorter = smaller spot
Beam Quality
Deviation from ideal Gaussian
M² = 1 is perfect
Focal Length
Focusing lens parameter
Shorter = tighter focus
Common Laser Wavelengths
Optimization Tips
Use shorter wavelengths for smaller spots
Larger beam diameter gives tighter focus
Shorter focal length reduces spot size
High-quality beams (low M²) focus better
Consider depth of focus for applications
Understanding Laser Beam Spot Size
What is Laser Spot Size?
Laser spot size is the diameter of the focused laser beam at its focal point. This parameter is crucial for applications requiring precise energy delivery, such as laser cutting, engraving, and medical procedures.
Key Applications
- •Laser cutting and engraving
- •Medical laser surgery
- •Semiconductor processing
- •Optical data storage
- •Scientific research and spectroscopy
Mathematical Foundation
S = (4 × M² × λ × f) / (π × d)
DOF = 2 × π × (S/2)² / (M² × λ)
- S: Spot size diameter (m)
- M²: Beam quality factor (dimensionless)
- λ: Wavelength (m)
- f: Focal length (m)
- d: Beam diameter at lens (m)
- DOF: Depth of focus (m)
Physics Note: The spot size is fundamentally limited by diffraction, making it impossible to focus a laser beam to an arbitrarily small size.
Beam Quality Factor (M²)
M² = 1
Perfect Gaussian beam - theoretical ideal with minimum spot size
M² = 1.1-1.3
High-quality laser - excellent for precision applications
M² > 2
Lower quality - larger spot size, suitable for general applications