High-resolution time-of-flight terahertz tomography using a femtosecond fiber laser

Abstract

High-resolution tomographic imaging is demonstrated using a reflection-type terahertz time-domain spectroscopy. To realize a practical system for general use, a robust all-fiber laser was used as the pump light source. Broadband terahertz waves were generated with the combination of optical pulses compressed to 17 fs using optical fibers and a DAST crystal. Using deconvolution signal processing, the wideband spectrum of the generated terahertz waves provided high-axial resolution leading to successful imaging of a multilayered structure containing a 2-microm-thin GaAs layer. To our knowledge, this is the first demonstration of terahertz tomographic imaging of such a thin layer.

Detailed non-destructive evaluation of UHMWPE composites in the terahertz range

“…It enables the precise analysis of the internal structure (the time-of-flight imaging). This method can be applied to the examination of thin samples (in the range of 1 cm), but with high axial resolution of about 30 µm (minimum layer separation distance) or even smaller (Takayanagi et al 2009). This resolution is proportional to the temporal width of the incoming pulse and inversely proportional to the group refractive index of the layer (Yasui et al 2005).…”

Terahertz Pulse Detection Techniques and Imaging Applications

“…One primary application of THz pulse detection is TPI, which can provide a three-dimensional (3D) map of the object by using the time of light of THz pulses [12]. TPI can be regarded as an extension of the THz-TDS.…”

Review of Terahertz Tomography Techniques

“…THz pulsed imaging has the unique feature of providing a 3D "map" of the object by using the time-of-flight of the reflected THz pulses [143]. In brief, a THz pulse is directed at the sample and the reflected beam is measured in amplitude and phase.…”

“…In this technique, as the arrival time of the THz waveforms can be determined with a femtosecond precision, the position of reflecting surfaces within the test object, can be resolved with accuracy of a several micrometers (provided consecutive reflections are resolved in time) [147]. For example, a very high depth resolution on the order of 1 μm has been demonstrated [148] (Fig.8).…”