Square-low detectors based on Zero-Bias Schottky Diodes High sensitivity
in ultra-wide frequency band and room-temperature operation make Schottky-barrier
diode (SBD) based Quasi-optical detectors the only alternative to Golay
Cell detectors for low-THz
frequency region. Bias-free operation allows for system simplicity and
ultra-low noise. In contrast to Golay Cell,the SBD detectors are simpler,
geometrically smaller,and much faster. The last criteria makes SBD the
device of choice for many applications.
§ Scientific instrumentation,
§ High bit rate telecommunication,
§ Monitoring of short-pulse and weak THz radiation.
ACST Quasi-optical Detectors consist on
three major parts:
1. A planar ultra-wideband antenna fed by a zero-bias
2. Optical lens,
These detectors are intrinsically very fast. For instance,
they are suitable to monitor very short THz impulses from a
synchrotron light source. An experiment done at ANKA, the
synchrotron Radiation Facility at Karlsruhe Institute of
Technology, demonstrated pulse length of just 25ps, which
was limited by reading electronics. This experiment suggest
ACST quasi optical detectors are probable one of the fastest
detectors reported to day.
Because of frequency-dependent optical beam forming,
the accurate estimation of absolute responsivity of quasi
optical detectors is not a trivial matter. Therefore,
comparative evaluation of Signal-to-Noise Ratio (SNR)
with a Golay Cell is usually practicable Figure-of-Merit for
quasi optical detectors from the user point of view. For
instance, detectors with th ehighest available RF-bandwidth
shows SNR better than of Golay Cell in frequency range up
to about 1THz, whereas at higher frequencies the Golay
Cell shows better SNR (see plots above).
Typical performance for detectors with different frequency ranges Typical packaging includes:
■ Lens: 12mm diameter, collimated.
■Polarisation: Linear or circular, depending on
used planar antenna
■Video amplifier Two versions available: DC-1MHz
bandwidth: and 10MHz-4GHz.
Detectors can also be packaged on customer specification.