The name is absent

wavelength: З cm 3 mm ЗОО urn 30 urn 3 μm
—______I________I________L-______________I__________

microwave          ΓHz          infrared visible

--------------------1---------------------1..........................................1-----------------------------------------1---------------------------
frequency: ioghz iooghz ithz iothz ∙∣oothz

Figure 1.1 : The terahertz region of the spectrum lies between microwaves and in-
frared, and is characterized by a free-space wavelength between 30 microns and 3
millimeters. The photon energy corresponding to kβT at room temperature, 40 meV,
is equivalent to a frequency of about 10 THz.

chanical scanning is slow; the acquisition time scales with resolution and the scan area.
State-of-the-art technology takes around 6 minutes to scan a IOOmmxlOOmm area
at 0.25mm resolution [2]. Other approaches, such as that pioneered by researchers
at MIT, involve the use of focal-plane techniques, similar to the pixel array inside a
digital camera, to achieve real-time THz imaging [3]. However, these systems tend to
have higher complexity and operational cost. For example, available array detectors,
such as microbolometer arrays, are relatively insensitive to THz radiation, so a bright
source is needed. Single-shot electro-optic sensing using crossed polarizers and a CCD
camera also allows video-rate THz imaging [4], but this method requires a large and
costly amplified femtosecond laser system. Yet, other recently developed imaging
systems using more sophisticated image processing approaches, such as the Radon
transform [5,6] and interferometric imaging [7], have shown preliminary successes
but also face similar limitations in speed, resolution and/or hardware requirements.
Clearly, novel imaging approaches are needed for improving the performance of tera-
hertz imaging.

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