Terahertz spectroscopic imaging using noncollinear electro-optic sampling and a multistep mirror without shifting the object

Norihiko Itani; Kazunori Maruyama; Shin-ya Hasegawa; Shinichi Wakana

doi:10.1117/12.928834

15 October 2012 Terahertz spectroscopic imaging using noncollinear electro-optic sampling and a multistep mirror without shifting the object

Norihiko Itani, Kazunori Maruyama, Shin-ya Hasegawa, Shinichi Wakana

Author Affiliations +

Proceedings Volume 8496, Terahertz Emitters, Receivers, and Applications III; 84960Z (2012) https://doi.org/10.1117/12.928834
Event: SPIE Optical Engineering + Applications, 2012, San Diego, California, United States

Abstract

We previously developed a high-speed terahertz spectroscopic imaging method based on electro-optic sampling with a noncollinear geometry of the THz beam and probe laser beam and using a multistep mirror in the path of the probe beam. We set the incident probe laser into MAST at a 45° angle, to prevent interference between adjacent beams. However, this produced beam vignetting, so imaging had to be performed twice, between sample movements, and this increased the imaging time accordingly. Thus, we improved the probe-laser imaging system after reflecting from the MAST to correct for the effects of diffraction. This prevents interference from adjacent beams and allows the angle of incidence on the MAST to be set to 0°, enabling the entire sample surface to be imaged in one measurement. As a result, we are able to perform measurements in 40 seconds, half the time of the previous method, and obtain a 28x28-pixel spectral image with spatial resolution of 1.07 mm. To verify the imaging performance, we also measured test samples, showing that the shape and thickness of items inside an opaque plastic case can be distinguished using amplitude and phase images, and metallic foreign objects can be detected. We also evaluated the method and were able to show the validity of the spectral imaging results by distinguishing the transmission or blocking of arbitrary frequency components.

Citation Download Citation

Norihiko Itani, Kazunori Maruyama, Shin-ya Hasegawa, and Shinichi Wakana "Terahertz spectroscopic imaging using noncollinear electro-optic sampling and a multistep mirror without shifting the object", Proc. SPIE 8496, Terahertz Emitters, Receivers, and Applications III, 84960Z (15 October 2012); https://doi.org/10.1117/12.928834

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KEYWORDS

Terahertz radiation

Laser beam diagnostics

Imaging spectroscopy

Crystals

Laser crystals

Spectroscopy

Mirrors

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