Laser Linewidth & Coherence Calculator

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Calculate spectral linewidth from coherence length or vice versa.

Spectral Parameters

Input Mode

Frequency Linewidth (Δν)

Center Wavelength (λ)

Calculation Results

Enter parameters to calculate linewidth

About this calculator

Quick Reference

ΔνFrequency linewidth

L_cCoherence length

ΔλWavelength linewidth

cSpeed of light

Overview

Laser linewidth is the width of the optical spectrum of a laser. It is inversely related to the coherence length—the distance over which the laser light remains in phase. Narrow linewidth lasers are essential for holography, spectroscopy, and fiber optic sensors.

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Pro Tips

Δν and L_c are related by the speed of light: Δν = c / (π * L_c) for a Lorentzian profile.
The narrower the linewidth, the longer the coherence length.
L_c = c / (π Δν) for Lorentzian, or L_c = c / Δν for rectangular spectra.

Fun Facts

"Most common laser pointers have a coherence length of only a few centimeters, while high-end ultra-stable lasers can have coherence lengths exceeding 1,000 kilometers!"
"The LIGO gravitational wave detector uses lasers with extremely narrow linewidths to detect vibrations smaller than the width of an atom."
"Expanding the universe actually increases the linewidth of distant starlight, a phenomenon known as redshift broadening."

Formula: L_c = c / (π * Δν) , Δλ = (λ² / c) * Δν