Download original image
Two possible geometrical constructions for relating group index ng to phase index n: (a) with the dependence in wavelength λ, i.e., the spatial period of the wave, the tangent T0(λ) to the phase index curve crosses the ordinate axis at the value ng(λ0) of the group index; (b) with the dependence in angular frequency ω, a double-slope line DS0(ω) is drawn from where the tangent T0(ω) to the phase index curve crosses the ordinate axis, and the group index ng(ω0) equates DS0(ω0).
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.