Extended Data Fig. 3: Dynamic gratings in ring lasers.
a–c, Beat patterns, calculated from the analytical model of a ring with a defect, that oscillate at the fundamental, second harmonic and third harmonic of the round-trip frequency frt. Patterns are shown both for the unwrapped angular coordinate (top) and as projected onto a two-dimensional ring (bottom). Here it is assumed that the counterpropagating optical beats have the same intensity. d–f, Different beat patterns calculated assuming various beat balance ratios rBB, that is, different relative intensities of the counterpropagating optical beats, as discussed in the text. Also shown are the electric fields of the clockwise (ECW) and counterclockwise (ECCW) waves (red curves). The wavenumber is small for visual representation. The black lines correspond to the envelope of the fields, from which the mean values ⟨E⟩ and modulation amplitudes ΔE are calculated. The three cases correspond to: unidirectional lasing, which gives a uniform beat power across the cavity (d); bidirectional lasing with counterpropagating optical beats that are not fully balanced, which gives a beat grating with limited fringe visibility (e); bidirectional lasing with fully balanced optical beats, which gives a dynamic grating with strongly suppressed nodes (f).
