Laser Linewidth and Bandwidth Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

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Small input changes can matter a lot in laser linewidth and bandwidth, especially when angles, squared dimensions, ratios, or logarithms are involved. Light calculations often combine tiny wavelengths with macroscopic distances, making unit discipline especially important. That is why the useful part of this calculator is the relationship as well as the headline value.

What this calculator does

The purpose of the Laser Linewidth and Bandwidth Calculator is to evaluate laser linewidth from Laser frequency, Cavity linewidth, Power. It is most useful for quick comparisons or hand-checks where the input definitions and displayed units remain part of the answer.

How to use it

Fill in the active quantities—Laser frequency, Cavity linewidth, Power, Fundamental wavelength, Wavelength bandwidth—and leave output-only boxes for the calculator to derive. Pay special attention to signs, angles, and whether a dimension is a radius, diameter, area, or length. Read the result together with its displayed unit.

How the calculation works

When laser frequency ν, cavity linewidth γ, and power P are supplied, the linewidth path uses Δν = πhνγ²/P. A second path converts a wavelength interval around λ into frequency bandwidth using c/(λ−Δλ/2) − c/(λ+Δλ/2). The two paths are related quantities but are entered independently on this page.

Example

With only the default 1064 nm wavelength filled in, the page has no ν, cavity linewidth, power, or wavelength-bandwidth pair from which to produce a nonzero linewidth, so the headline remains 0 Hz. Add the inputs for the path you actually want to evaluate before interpreting the output.

How to interpret the result

Interpret the laser linewidth together with the supporting optical values rather than in isolation. If changing wavelength, focal length, or angle produces a trend opposite to the equation, recheck the sign convention and selected unit before drawing a conclusion.

Limitations and notes

The default form contains only a wavelength, so the linewidth headline remains 0 until frequency, cavity linewidth, and power are supplied. The formula is a simplified linewidth relation; real lasers can be broadened by technical noise, cavity dynamics, temperature, and measurement bandwidth.