Beam diameter at focus: μm
Depth of field: μm
This Laser Beam Spot Size Calculator is a web-based tool designed to calculate the focused spot size and depth of field of a collimated Gaussian laser beam. It takes various input parameters and performs the calculations based on standard formulas.
Input Parameters
- Beam Diameter at Lens (1/e²)
- This is the diameter of the laser beam at the lens, measured at the 1/e² intensity level.
- You can enter the value and select the unit (μm, mm, or cm) from the dropdown menu.
- Lens Focal Length
- This is the focal length of the lens used to focus the laser beam.
- Enter the value and select the unit (mm or cm) from the dropdown menu.
- Wavelength
- This is the wavelength of the laser beam.
- Input the value and choose the unit (pm, nm, μm, or mm) from the dropdown menu.
- Beam Quality (M²)
- This is the beam quality factor, also known as M², which accounts for deviations from an ideal Gaussian beam.
- Enter the value directly in the input field.
Output Parameters
- Beam Diameter at Focus
- This is the calculated diameter of the focused laser beam spot size.
- The result is displayed in micrometers (μm).
- Depth of Field
- This represents the distance over which the focused beam remains within a specified range of diameters.
- The result is displayed in micrometers (μm).
How to Use the Calculator
- Enter the values for the input parameters (beam diameter, lens focal length, wavelength, and beam quality) along with the appropriate units.
- Click the “Calculate” button to perform the calculations.
- The calculated spot size and depth of field will be displayed in the output section.
- If you want to reset the calculator to the default values, click the “Reset” button.
Considerations for Laser Beam Spot Size Calculation
When calculating the laser beam spot size, it’s important to consider the following:
- Lens Quality: The formulas assume that the focusing lens has minimal aberrations and distortions. Lenses with significant aberrations may affect the spot size calculations.
- Lens Diameter: The lens diameter should be at least twice the input beam diameter to avoid clipping the “wings” of the Gaussian profile.
- Beam Quality (M²): The beam quality factor accounts for deviations from an ideal Gaussian beam. A higher M² value indicates a poorer beam quality and a larger spot size.
Relevant Formulas
The Laser Beam Spot Size Calculator uses the following formulas:
Beam Diameter at Focus (Spot Size):
\(Beam\ Diameter\ at\ Focus=2w0=\frac{4M^2λf}{\pi D}\)
Where:
- M² is the beam quality factor
- λ is the wavelength
- f is the lens focal length
- D is the beam diameter at the lens (1/e²)
Depth of Field:
\(Depth\ of\ Field=2zR=2\frac{\pi w\frac{2}{0}}{M^2λ}\)
Where:
- zR is the Rayleigh range
- w₀ is the beam radius at the focus (Spot Size / 2)
- M² is the beam quality factor
- λ is the wavelength
The depth of field calculation considers the increased divergence due to the beam quality factor M², which accounts for deviations from an ideal Gaussian beam. This parameter is relevant when focusing the beam into a nonlinear crystal for applications like second harmonic generation.
Considering these formulas and factors, you can accurately calculate the focused spot size and depth of field for your laser beam setup, enabling precise control and optimization of laser-based applications.
