Use this laser calculation or lookup for a first-pass optics, pulse, beam, gain-medium, diode, fiber, or safety comparison under explicitly stated wavelength and operating conditions.

Core radius (µm)

Core radius of the step-index fiber.

Wavelength (nm)

Operating vacuum wavelength.

n_core

Refractive index of the core (must exceed cladding).

n_clad

Refractive index of the cladding.

Convert step-index fiber core/cladding indices, core radius, and wavelength into numerical aperture, V-number, and Marcuse mode-field diameter. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

NA

Numerical aperture sqrt(nCore^2 - nClad^2).

V-number

Normalized frequency V = 2π·a·NA/λ.

MFD (µm)

Marcuse Gaussian-spot mode-field diameter estimate.

Single mode

True when V < 2.405 (single LP01 mode only).

Marcuse fit applicable

True in the commonly used 1.2 ≤ V ≤ 2.405 range of the Marcuse fit.

• Laser behavior depends on wavelength, mode, coherence, pulse shape, beam quality, cavity and optical losses, material data, temperature, alignment, nonlinear effects, damage thresholds, and measurement definitions. Lookup values are not substitutes for current device data or laser-safety analysis.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Verify constants and limits with primary literature and manufacturer data, propagate tolerances, model the complete optical train, and apply the relevant laser safety standard.

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