Biomedical Engineering Reference
In-Depth Information
Figure 8.1
Local topological features in the optical phase field and
powerflow. (a) Phase saddle node—a stationary point (or line) where the
phase gradient vanishes. (b) Optical phase singularity—a point (or line) of
destructive interference where the field intensity vanishes and the phase
is undefined (i.e., all values of phase from 0 to 2
coexist). (c) The optical
powerflow saddle point corresponding to the phase saddle point in (a). (d)
Theopticalpowerflowvortex corresponding tothephasesingularity in(b).
π
lines in space where the field intensity is zero due to destructive
interference. At these phase singularities, the phase of the field is
undefined. Other types of local topological features are stationary
phase nodes-points or lines in space where the phase gradient
vanishes [27, 30-33]. The stationary phase nodes include local
extrema (i.e., phase maxima and minima) as well as phase saddle
nodes as shown in Fig. 8.1a.
Because the optical power always flows in the direction of
the phase change, the phase maxima (minima) give rise to the
powerflow sinks (sources) while phase saddle points give rise to
