http://www.terahertz.co.uk/index.php?option=com_content&view=article&id=204&Itemid=583
THz detector systems
QMC Instruments Ltd. has nearly forty years experience in the design and manufacture of cryogenic Terahertz detectors. Our unique combination of technologies permit the creation of individually designed systems resulting in performance that is optimised for each experiment.
We offer a range of cryogenic detectors which are sold as stand-alone items, or as systems packaged with our own cryostats, optics, filters and amplifiers. By cryogenic we mean that they operate at temperatures of 4 K (-269 °C) and below, either using liquid helium or a mechanical cooler. While the thought of cryogenic operation may be off-putting, operatirng a mechanically cooled system is extremely straightforward.
For applications that do not require as high sensitivity we offer an excellent pyroelectric detector that operates at room temperature.
All of our products are optically calibrated and come with a two year guarantee.
Our detector types are listed below; select a link for more information. Example detector system manuals are also available, and please contact us if you cannot find what you are looking for.
Cooled detectors
Room temperature detectors
Choosing a detector
| Superconducting bolometers are sensitive to a wide range of wavelengths. Their bandwidth ranges from 3 mm (100 GHz or 3.3 cm-1) to 15 microns (20 THz or 600 cm-1). As well as extremely high sensitivity, these detectors offer a linear dynamic range over 50 dB and constant sensitivity as a function of wavelength. The use of our unique multi-mesh filters means that observation bandwidth can be carefully and accurately controlled and detectors operate with optimised sensitivity as they are not unnecessarily degraded by exposure to background power at unwanted frequencies. |  |
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Indium Antimonide (InSb) hot electron bolometers (HEBs) and doped Germanium photoconductors offer a much greater speed of response than composite bolometers with no reduction in sensitivity. The disadvantage of these detectors is that the range of frequencies to which they are sensitive is somewhat smaller. The two detector types are useful over different frequency ranges. InSb detectors are useful at frequencies up to 500 GHz or 2.5 THz depending on type, while photoconductors are useful at frequencies above approximately 1.5 THz.
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The photograph above is of one of our InSb hot-electron bolometers. The detector area and volume is quite large compared to other detector technologies. This leads to good sensitivity at long wavelengths and high linear dynamic range.
Our detectors can be purchased as stand-alone units or as a fully assembled, tested and calibrated system ready for use. Cooling can be either using liquid helium or mechanical coolers. Mechanicaly cooled systems cool to operating temperature with no user intervention. Our liquid helium cryostats are designed and built to our specifications by our sister company, Thomas Keating Ltd. These cryostats offer the convenience of very long run-times. Cryostat operation is straightforward, and detector systems come with a comprehensive range of safety devices as standard.
The photograph to the right shows a fully assembled bolometer system. The bolometer is cooled to 8 K by a mechanical (pulse tube) cooler. It views the outside world through a vacuum window. The system has its own low-noise preamplifier.
When the lower sensitivity of pyroelectric detectors is acceptable, they provide a less expensive alternative to cryogenic detector systems.
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