160
A. Saha
Fig. 6 a Primary components of the bolometer. b Rise and fall of the temperature in the absorber
as a function of time. Adapted with permission from [30] © The Optical Society
T A relaxes back with the same time constant to T s . A resistive thermometer which is
connected to the absorber measures the change in temperature as shown in Fig. 6a.
Advantage of microbolometers is that their operation principle is not wavelengthspecific. So, microbolometers which were initially used for real-time THz imaging
were actually commercial microbolometers designed for infrared radiation [82–85].
Actually, microbolometers happen to be arrays of bolometers which are mounted onto
readout integrated circuits for focal-plane camera operation. Of late, microbolometers which can operate in the THz range were specifically designed. In fact, they
achieved NEP in the range of 10
−16 W/
√
Hz [86], when background thermal noise
was removed by cooling at cryogenic temperatures. However, microbolometers can
show high sensitivities even at room temperatures with proper design modifications.
This opens the possibility of using them for various industrial imaging applications.
Several research works are being carried on in this regard on increasing sensitivity and faster response time of the detectors. In the sub-THz region, generally the
microbolometers are underperforming, and hence to increase the sensitivity, resonant
cavity structure [87] was used. To develop a very fast-operating real-time spectrometer, microbolometer was used in conjunction with a diffraction grating [88]. In order
to increase the terahertz radiation, absorption metamaterials are also investigated
[89–93].
5 Applications
Wide ranges of applications are opening up with advances of terahertz sources and
detection techniques. In this section, few THz applications from different research
areas are discussed. Some very interesting imaging applications in THz region is
found in the areas of medical applications like 2D and 3D imaging, which includes
A. Saha
Fig. 6 a Primary components of the bolometer. b Rise and fall of the temperature in the absorber
as a function of time. Adapted with permission from [30] © The Optical Society
T A relaxes back with the same time constant to T s . A resistive thermometer which is
connected to the absorber measures the change in temperature as shown in Fig. 6a.
Advantage of microbolometers is that their operation principle is not wavelengthspecific. So, microbolometers which were initially used for real-time THz imaging
were actually commercial microbolometers designed for infrared radiation [82–85].
Actually, microbolometers happen to be arrays of bolometers which are mounted onto
readout integrated circuits for focal-plane camera operation. Of late, microbolometers which can operate in the THz range were specifically designed. In fact, they
achieved NEP in the range of 10
−16 W/
√
Hz [86], when background thermal noise
was removed by cooling at cryogenic temperatures. However, microbolometers can
show high sensitivities even at room temperatures with proper design modifications.
This opens the possibility of using them for various industrial imaging applications.
Several research works are being carried on in this regard on increasing sensitivity and faster response time of the detectors. In the sub-THz region, generally the
microbolometers are underperforming, and hence to increase the sensitivity, resonant
cavity structure [87] was used. To develop a very fast-operating real-time spectrometer, microbolometer was used in conjunction with a diffraction grating [88]. In order
to increase the terahertz radiation, absorption metamaterials are also investigated
[89–93].
5 Applications
Wide ranges of applications are opening up with advances of terahertz sources and
detection techniques. In this section, few THz applications from different research
areas are discussed. Some very interesting imaging applications in THz region is
found in the areas of medical applications like 2D and 3D imaging, which includes