## 1 Introduction  
Terahertz (THz) imaging and spectroscopy revealed itself as promising technologies for a large variety of applications [1]. Because of non-ionizing nature of THz radiation, imaging in this range can be found as a beneficial tool for medicine and biomedical stuff inspection [2; 3; 4]. As THz frequencies display the ability to propagate in dielectric medium without strong attenuation, THz imaging and spectroscopy can also serve as valuable instruments for security needs [5; 6; 7], post packages inspection [8; 9; 10] or industrial materials control and their identification [11; 12; 13; 14]. However, direct implementation of THz technology still meets severe difficulties related mainly to reliability of active components (emitters and detectors) and issues of precise alignment of the optical system due to the presence, as a rule, of passive bulky optical elements like mirrors, lenses or beam splitters. Thus, effective and convenient operation under real environmental conditions still needs to overcome alignment and compact optics problems [15]. On the other hand, it is of decisive demand to provide adequate and favourable control of the spatial mode profile of illumination. In particular, it has strong impact in THz spectroscopy for quality of recorded THz spectra in increasing its bandwidth, lowering the noise floor, as well as by reducing uncertainties in observational data [16; 17; 18]. It displays also important role in THz imaging, especially, in examining bulky objects when extraordinary means are needed to be applied in THz beam engineering aiming to provide appropriate image quality [19; 20]. Spatial mode profiles of discrete THz spectrum radiation from backward wave oscillators and quantum cascade lasers were already studied by employing thin film vanadium oxide (VOx) based bolometers [21]. Moreover, image of the beam emitted by an optoelectronical THz time-domain spectrometer was recorded using a camera integrating an array of THz optimized antenna-coupled amorphous silicon-based microbolometers [22]. Indeed, it is of distinct interest as THz time-domain spectrometers become widespread, they require precise alignment to get well collimated THz beams, hence, it is beneficial to engage easy-to-use imaging detector to accurately adjust these optical systems. The sensitivity of the presented microbolometers allowed to register images of spatial mode profiles as well as video images despite the fact that their average power was in the range of a few \(\upmu\)W [22]. The developed and described here antenna-coupled titanium-based microbolometer (Ti-mB) [23] was initially applied in compact THz imaging systems for security aims [24; 25]. Its high sensitivity was successfully exploited also in medical applications via direct THz imaging of carcinoma affected tissues [26]. In a given work, by coupling of the titanium microbolometers with relevant resonant antennas, we modified these sensitive detectors into universal, convenient and easy-to-use imaging instruments well-suited to accurately adjust weak power THz sources without additional focusing components. They can be employed in imaging systems operating either in time-domain or in continuous wave modes for precise alignment and control of their spatial mode profiles. Versatile operation of the devices is displayed engaging different kinds of THz emitters - electronic multiplier sources (THz ELS), optical THz mixer-based frequency domain (THz FDS) and femtosecond optoelectronic THz time domain (THz TDS) spectrometers as well as optically pumped molecular THz laser (THz OPML). Features of the microbolometers coupled with resonant antennas in subTHz range, within the 0.15-0.6 THz range, are exposed and discussed here. The ability to monitor spatial mode profile even far above the antennas resonances, up to 2.52 THz, is explored. Moreover, the possibilities of polarization-sensitive mode control are examined in details, and the recorded mode control results are compared with that obtained using commercially available pyroelectric sensors.