The frequency region of 0.3 to 10.0THz, also known as the far infrared or submillimeter range, is at the core of an explosion of research in the field of terahertz imaging and detection.This has been largely driven by the versatility of the technology and its possible use in applications that would otherwise prove to be impractical, if not impossible, with conventional technologies. One of the first uses of THz imaging, for example, was for the detection of dark matter in the demanding field of astronomy. This area requires tools of tremendous sensitivity. Such sensitivity requires low noise detectors for which the only solution is to use cryogenic detectors cooled below 300 mK. Similarly,THz spectroscopy has the potential to become a powerful tool for the investigation of DNA and RNA topology.The far infrared absorption spectra of nucleic acids reflect low-frequency internalmolecular motions that are dependent upon the weak hydrogen bonds of th edouble-helix base-pairs and non-bonded interactions between different functional groups. This could, in turn, provide information on the structure, flexibility and function of the examined molecule.
We offer a wide range of cryostats which can be fitted with windows suitable for Terahertz applications.
The range includes:
Optical cryostats achieving base temperature around 1.5 K or 4 K.
Helium 3 refrigerators for temperatures around 300 mK
Dilution refrigerators for temperatures around 10 mK
The primary obstacle to the development of THz cryosensors, regardless of their purpose, has been in the cost and complexity of handling the liquid helium and cryostats used to cool sensors. The advent in Cryogen-free technology over the last few years has brought a new approach to this problem. Cryofree products do not require servicing or replenishing of liquid cryogens, making significantly easier to use and far less costly to operate than conventional helium cryostats.
Now most cryostats are available as Cryofree®.
Suitable windows for Terahertz include:
- Not transparent in visible and near-IR spectral ranges, so can be used to block light.
- Offer the best performance at frequencies below 1 THz and above 7 THz
Polished Tsurupica windows focus THz and visible light. Tsurupica is highly transparent in Tz and visible spectral ranges
Diamond windows: optical transparency in the UV, visible, IR and far infrared.
Examples of systems used for Terahertz applications:
A team of researchers from the Microtechnology Department of Chalmers University of Technology (Göteborg, Sweden) has designed a prototype Terahertz
Transmission Spectrometer (TTS) in the 0.2 to 2.0 THz frequency range, with a resolution down to 1.0 GHz. Importantly, the prototype also comprised a cold
electron bolometer (CEB) detector and broadband, narrow line width oscillator employing superconducting nanotechnology. Through a mechanism similar to the Peltier effect, superconductor-insulator-normal (SIN) tunnel junctions contained within the CEB provide the system with further electron cooling, down to just 100 mK when a simple 0.5 mV dc bias voltage is applied. This creates the basic model for a gas analyser capable of detecting trace amounts of poisonous or explosive materials in the air of security risk areas such as airports and government buildings. In addition, the system could be used for applications in security imaging, including the detection of concealed weapons in an active or passive manner.