InSb hot electron bolometer
High sensitivity and low noise
Fast operating speeds of ~500 KHz
Tuneable peak frequency up to 2.5 THz
Can be arrayed
Available in wet or dry systems
Indium antimonide (InSb) bolometers offer much shorter time constants than composite germanium bolometers or Nb TES bolometers, at the expense of a narrower range of operating frequencies. Sensitivity at frequencies above 500 GHz can be improved with magnetically enhanced versions of this detector.
QMC Instruments Ltd. offers a high sensitivity InSb hot-electron bolometer that can be operated at 4.2 K. The detector is most commonly mounted in an optical integrating cavity behind Winston Cone coupling optics along with low-pass filters which ensure that unwanted higher frequencies are efficiently rejected.
An InSb (size 5 mm x 4.7 mm x 300 um) detector mounted on a quartz substrate is shown in the picture above. Detectors can be purchased as a stand-alone unit or as part of a fully assembled, tested and calibrated detector system ready for use.
We offer 3 different types:
Our QFI X is a meander of InSb that is highly sensitive to frequencies between 60 - 500 GHz, whilst providing fast response times.
The homogeneously tuned detector – model QFI/XB which uses a uniform magnetic field exposure, creating a single peaked response function. The peak frequency can be tuned between 1.5 and 2.5 THz and the typical peak width is 300 GHz at full-width-half-maximum.
Please see graph below for how our magnetically tuned detectors compare:
The inhomogeneously tuned detector – model QFI/XBI uses a varying magnetic field strength across the detector. The resonance is therefore integrated over a wider frequency range up to a maximum of 1.5 THz
Indium Antimonide (InSb) is a III-V semiconductor used commonly as a detector in the near-infrared. At 4.2 K the electron-phonon interactions are very weak, compared to the electron-electron interactions. This means that the absorption of long wavelength radiation can drive the electrons out of thermal equilibrium with the lattice to a hotter temperature. Termed the hot-electron response, it was first predicted by E.H.Putley in 1960. Since the resistance of the InSb depends on the electron temperature, then the resistance can be used as a thermometer of the electron system, and therefore indirectly a monitor of the incident radiation.
In InSb at 4.2 K the absorption will be constant up to 500 GHz, beyond which it falls as the signal frequency to the power -1.8. The result is that the unassisted detector (model QFI/X) loses a factor of almost 10 in sensitivity at 1.5 THz and more than a factor of 20 at 2.5 THz. However, by applying a magnetic field we can shift the absorption to higher frequencies.
Notes on specification
Detector optical responsivity is specified at 275 GHz
Detector optical NEP is specified at 275 GHz (1 kHz modulation)