1. What is Laser Beam Waist?

The laser beam waist (w₀) is the minimum radius of a laser beam where the beam is most focused. It's a fundamental parameter in Gaussian beam optics that describes the beam's spatial characteristics.

2. How Does the Calculator Work?

The calculator uses the beam waist formula:

Where:

• \( w_0 \) — Beam waist radius (m)
• \( \lambda \) — Laser wavelength (m)
• \( \theta \) — Beam divergence angle (rad)

Explanation: The beam waist is inversely proportional to the divergence angle - more collimated beams (small θ) have larger waists.

3. Importance of Beam Waist Calculation

Details: Knowing the beam waist is crucial for laser system design, optical alignment, focusing applications, and understanding beam propagation characteristics.

4. Using the Calculator

Tips: Enter wavelength in meters and divergence angle in radians. Both values must be positive numbers. For typical lasers, wavelengths are often in nanometers (convert to meters by multiplying by 10⁻⁹).

5. Frequently Asked Questions (FAQ)

Q1: What is the relationship between beam waist and Rayleigh range?
A: Rayleigh range (z_R) is related to beam waist by \( z_R = \pi w_0^2 / \lambda \), describing the distance over which the beam remains approximately collimated.

Q2: How does beam waist affect focusing?
A: Smaller beam waists allow for tighter focusing but result in shorter depth of focus and greater divergence.

Q3: What's typical beam waist size for common lasers?
A: For a HeNe laser (632.8 nm) with 1 mrad divergence, waist is about 0.2 mm. Diode lasers often have smaller waists due to higher divergence.

Q4: How to measure beam divergence angle?
A: Measure beam diameter at two points along propagation axis and calculate angle from diameter change over distance.

Q5: Does this formula work for non-Gaussian beams?
A: This exact formula applies to fundamental Gaussian modes. Multimode beams require different treatment using M² factor.