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 Features
 The following range of pyroelectric sensor heads is
suitable for direct connection to an oscilloscope or to the
LEM 2410 Power and Energy Meter.
To give an improved signal size and to improve noise performance,
pre-amplifiers can be used. Also available are
special heads for high power applications and for VUV (157nm) F2 laser
measurements.
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Pyroelectric pulsed laser energy detectors with black
absorption coating for high sensitivity - Series
PEM |
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HiRep Laser energy detectors designed for high repetition
rates - Series PEM HiRep |
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Pyroelectric pulsed laser energy detectors with metallic
absorption coating - Series PEM HR |
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Pyroelectric pulsed laser energy detectors with ceramic
absorption coating for high power densities - Series PEM
K |
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Laser energy detector with integrated pre-amplifier -
Series PEM E |
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VUV laser energy detector for use with F2 lasers -
Series PEM VUV |
Pyroelectric sensors can be classified as thermal
detectors. They provide wavelength independent conversion of light pulses into
voltage pulses. These detectors are built using a coaxial design and are
therefore extremely insensitive to electromagnetic interference (eg pulsed gas
lasers).
To satisfy the requirements of different applications,
detectors are available with diameters of 4 to 50mm. It is advisable to choose
a detector having a slightly larger area than the cross-section of the beam to
be measured.
The detectors have a black absorption coating which
possesses uniform absorption over the wavelength range from 185nm to
25µm.
The comparatively high sensitivity of these detectors is
particularly useful. Due to the insensitivity to electromagnetic interference,
it permits laser pulse measurements in the mJ range without any additional
amplification.
The maximum pulse repetition rate depends on the
internal capacitance of the detector as well as the load resistor. All the
detectors can be connected directly to the 1M Ohm input BNC socket of an
oscilloscope. A smaller load resistor can be used to obtain the highest pulse
repetition rate. Repetition rates of up to 100 Hz are then possible. A 100K Ohm
load resistor is included with each head. The sensitivity of the detectors is
specified for both 1M Ohm and 100K Ohm load resistors.
The pyroelectric effect, in general, allows temperature
changes to be measured. Thus these detectors are only suitable for detecting
pulsed or modulated radiation. There are no limitations as to how narrow pulses
can be, as the energy of the pulse is converted into heat flow in the
absorption layer. The maximum pulse duration is estimated from the RC time
constant (sensor capacitance x load resistance), assuming the thermal time
constant (thermal dissipation from the sensor into the heat sink) has no
effect. All the sensors offered here can be used to measure pulse widths of up
to about 2 ms, so they can be used to measure most of the usual sources of
pulsed radiation.
It is possible to pulse a continuous light source by
using an instrument such as an optical chopper if required.
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