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.

Rod length (mm)

Gain length of the rod.

Wavelength (nm)

Lasing wavelength.

Internal loss (cm⁻¹)

Internal loss per centimetre of the crystal.

Sigma_e (cm²)

Stimulated emission cross-section of the transition.

R_rear

Rear high reflector.

R_output

Output coupler reflectivity.

Solve the four-level round-trip gain condition of a Nd:YAG cavity for the threshold population inversion and its stored energy density. 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]

ΔN_th (cm⁻³)

Population inversion density at laser threshold.

Stored energy density (J/cm³)

Stored energy density held by that inversion.

• 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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