 This equation was originally derived from classical optics.However, in 1992 Duarte derived this equation from quantum interferometric principles, thus linking a quantum expression with the overall intracavity angular dispersion.An optimized multiple-prism grating laser oscillator can deliver pulse emission in the kW regime at single-longitudinal-mode linewidths of formula_105 ≈ 350 MHz (equivalent to formula_106 ≈ 0.0004 nm at a laser wavelength of 590 nm).