Abstract-High-speed frequency-domain terahertz coherence tomography

Ji Sang Yahng, Choon-Su Park, Hwi Don Lee, Chang-Seok Kim, and Dae-Su Yee
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-2-1053

High-speed frequency-domain terahertz (THz) coherence tomography is demonstrated using frequency sweeping of continuous-wave THz radiation and beam steering. For axial scanning, THz frequency sweeping with a kHz sweep rate and a THz sweep range is executed using THz photomixing with an optical beat source consisting of a wavelength-swept laser and a distributed feedback laser diode. During the frequency sweep, frequency-domain THz interferograms are measured using coherent homodyne detection employing signal averaging for noise reduction and used as axial-scan data via fast Fourier transform. Axial-scan data are acquired while scanning a transverse range of 100 × 100 mm2 by use of a THz beam scanner with moving neither sample nor THz transmitter/receiver unit. It takes 100 s to acquire axial-scan data for 100 × 100 points with 5 averaged traces at a sweep rate of 1 kHz. THz tomographic images of a glass fiber reinforced polymer sample with artificial internal defects are presented, acquired using the tomography system.

© 2016 Optical Society of America

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Abstract-High-speed terahertz reflection three-dimensional imaging using beam steering

High-speed terahertz reflection three-dimensional imaging using beam steering Dae-Su Yee, Kyong Hwan Jin, Ji Sang Yahng, Ho-Soon Yang, Chi Yup Kim, and Jong Chul Ye  »View Author Affiliations

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-23-4-5027

Optics Express, Vol. 23, Issue 4, pp. 5027-5034 (2015)
http://dx.doi.org/10.1364/OE.23.005027

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High-speed terahertz (THz) reflection three-dimensional (3D) imaging is demonstrated using electronically-controlled optical sampling (ECOPS) and beam steering. ECOPS measurement is used for scanning an axial range of 7.8 mm in free space at 1 kHz scan rate while a transverse range of 100 × 100 mm² is scanned using beam steering instead of moving an imaging target. Telecentric f-θ lenses with axial and non-axial symmetry have been developed for beam steering. It is experimentally demonstrated that the non-axially symmetric lens has better characteristics than the axially symmetric lens. The total scan time depends on the number of points in a transverse range. For example, it takes 40 s for 200 × 200 points and 10 s for 100 × 100 points. To demonstrate the application of the imaging technique to nondestructive testing, THz 3D tomographic images of a glass fiber reinforced polymer sample with artificial internal defects have been acquired using the lenses for comparison.

© 2015 Optical Society of America