phase matching
the condition that the
phase of the nonlinear polarization bears a
spatially fixed relation to that of the optical
field generated by the polarization. This con-
dition is a requirement for high efficiency in
nonlinear optical generation processes.
phase modulation
a type of angle modu-
lation whereby information is encoded onto
a carrier wave by modifying its phase angle
as a function of time in proportion to the in-
telligence signal amplitude.
phase modulator
a device that alters the
phase of a signal.
phase noise
frequency variation in a car-
rier signal that appears as energy at frequen-
cies other than the carrier frequency.
phase only binary filter
transmission or
reflection phase plate in which neighboring
regions differ in phase shift by pi radians.
phase parameter
complex parameter rep-
resenting corrections to the gain and phase of
a Gaussian beam.
phase plane
a two-dimensional state
space.
phase plate
transparent medium that in-
troduces different phase shifts to different
transverse regions of an optical wave for the
purpose of introducing or reducing phase or
amplitude structure on the wave; often hav-
ing only two phase shift values differing by
π.
phase portrait
many different trajectories
of a second-order dynamical system plotted
in the phase plane.
phase response
the way in which a system
alters the phase of an input sinusoid.
phase ripple
the variation in phase re-
sponse across the operating bandwidth of an
optical or electrical device.
phase sensitive detection
See
synchronous
detection
.
phase sensitive measurement
measure-
ment in which the phase of an AC signal is
tracked in a feedback loop in order to improve
detection sensitivity. The most common ex-
amples are phase-locked loops in control sys-
tems and lock-in amplifier measurements in
electronics. In the latter, a small AC sig-
nal is added to the bias voltage supply, and
this signal is then detected in any measured
quantity with an amplifier whose phase can
be varied to “lock onto” that of the initial AC
signal. This effectively mixes the two AC
signals, and their difference (at DC) is used to
characterize the measurement. The effective
bandwidth is determined by the bandwidth at
the DC level.
phase sequence
describes the rotational
orientation of the voltage phasors in a 3-
phase electrical power system. A positive
phase sequence, designated by the nomen-
clature ABC, indicates a 3-phase connection
in which the B phase voltage lags the A phase
voltage by 120 degrees, and the C phase volt-
age leads the A phase voltage by 120 degrees.
A negative phase sequence, designated by
ACB, reverses this relationship so that the
B phase leads the A phase, and the C phase
lags the A phase. See also
phase sequence
indicator
.
phase sequence indicator
device used
to detect the phase sequence of a 3-phase
electrical power system.
See also
phase
sequence
.
phase shift
a time displacement of a wave-
form with respect to another waveform of the
same frequency.
phase shifter
a device that changes the
phase angle between two buses in a power
system. Conventional phase shifters are spe-
cial autotransformers in with each phase volt-
age in connected in series with a variable
component of voltage from another phase.
c
2000 by CRC Press LLC