types of pyroelectric detectors are optimized for application in THz
region. The detectors are small, have a large active area and a short
basic principle of pyroelectric detection is that the radiation pulse
coming from a pulsed laser or a chopped cw-laser is absorbed in an
absorber sheet. From there the heat energy is transferred to the
pyroelectric sensor material by heat conduction. For all types of THz
detectors a broadband metallic absorber is used. For realizing
broadband absorption a partial absorption of nearly 50 % is realized,
whereas 25% are reflected and the 25% transmitted radiation is absorbed
in a dump. A temperature change of the
sensor material leads to a generation of a free charge at two opposite
surfaces of the sensor. The thermal time constant (τtherm) describes the relaxation of the sensor temperature to the ambient temperature.
THz detection system consists of a detector and a current preamplifier.
It is optimized for application in connection with cw- lasers and a
response of a pyroelectric detector can be very fast, but for a
reduction of noise the bandwidth of the preamplifier is limited. A
further reduction of noise is possible by using detectors with smaller
active area. The actual bandwidth depends on the frequency limit and is
given in the preamplifier datasheet. Two possibilities for a
Signal/Noise improvement for continuously repeated signals are often
-Lock in amplification.
detectors are calibrated from PTB Germany at a wavelength of 2.52 THz
in combination with a preamplifier. Other conditions on request.
calibration of the detector is done without any window. Under these
conditions any movement of air must be avoided. We deliver the detector
with a protection cap having a THz transparent insert. This cap can be
used for avoiding any type of disturbance from moving air or fans. You
have to check if this cap can be used for your wavelength and have in
mind that the calibration is done without this cap. Furthermore it is
advisable to tilt the detector a little bit against the optical axes
for avoiding reflexions back to the source.