Abstract-Diffraction-limited real-time terahertz imaging by optical frequency up-conversion in a DAST crystal

Diffraction-limited real-time terahertz imaging by optical frequency up-conversion in a DAST crystal Shuzhen Fan, Feng Qi, Takashi Notake, Kouji Nawata, Yuma Takida, Takeshi Matsukawa, and Hiroaki Minamide  »View Author Affiliations

Optics Express, Vol. 23, Issue 6, pp. 7611-7618 (2015)
http://dx.doi.org/10.1364/OE.23.007611

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-23-6-7611

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Real-time terahertz (THz) wave imaging has wide applications in areas such as security, industry, biology, medicine, pharmacy, and the arts. This report describes real-time room-temperature THz imaging by nonlinear optical frequency up-conversion in an organic 4-dimethylamino-N’-methyl-4’-stilbazolium tosylate (DAST) crystal, with high resolution reaching the diffraction limit. THz-wave images were converted to the near infrared region and then captured using an InGaAs camera in a tandem imaging system. The resolution of the imaging system was analyzed. Diffraction and interference of THz wave were observed in the experiments. Videos are supplied to show the interference pattern variation that occurs with sample moving and tilting.

© 2015 Optical Society of America

Abstract-10 aJ-level sensing of nanosecond pulse below 10 THz by frequency upconversion detection via DAST crystal: more than a 4 K bolometer

Feng Qi, Shuzhen Fan, Takashi Notake, Koji Nawata, Takeshi Matsukawa, Yuma Takida, and Hiroaki Minamide  »View Author Affiliations

Optics Letters, Vol. 39, Issue 5, pp. 1294-1297 (2014)
http://dx.doi.org/10.1364/OL.39.001294

10 aJ-level sensing of nanosecond pulse below 10 THz by frequency upconversion detection via DAST crystal: more than a 4 K bolometer

By using frequency upconversion detection of terahertz (THz) waves via 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) crystal with an optimized frequency conversion process, ultrahigh sensitivity has been achieved. Direct comparisons with a 4 K bolometer were implemented. By using a simple positive intrinsic negative (PIN) diode without either electrical amplification or optical amplification, frequency upconversion detection can compete with the commercial 4 K bolometer, while by replacing the PIN diode with an avalanche photo diode (APD), it performs more than three orders better than the 4 K bolometer. Based on power calibration, the minimum detectable THz pulse energy is in the order of 10 aJ (9–25 aJ) at 4.3 THz, with a pulse duration of 6 ns. Thus, the minimum number of THz photons that can be detected is down to the order of 103 at room temperature. The current THz detection system gives a noise equivalent power (NEP) in the order of 100  fW/Hz1/2 (50–128  fW/Hz1/2). Moreover, by switching current optical detectors, the dynamic range is over six orders.

© 2014 Optical Society of America

Abstract-Broadband terahertz wave generation from a MgO:LiNbO3 ridge waveguide pumped by a 1.5 μm femtosecond fiber laser

Shuzhen Fan, Hajime Takeuchi, Toshihiko Ouchi, Kei Takeya, and Kodo Kawase

http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-38-10-1654

Cherenkov phase-matched terahertz (THz) wave generation from a MgO:LiNbO3 ridge waveguide was studied using optical rectification. Pumping was achieved using 20 and 60  fs laser pulses from a fiber laser centered at 1.56 μm. Time-domain spectroscopy (TDS) results showed a single-cycle pulse with 20  fs pulse pumping and a near-single-cycle pulse with 60  fs pulse pumping. The spectrum covered the range of 0.1–7 THz, with a signal-to-noise ratio of over 50  dB. The output power measured by a Si bolometer and a deuterated triglycine sulfate pyroelectric detector is shown and compared to that of a commercial photoconductive antenna. This system is believed to be a promising THz source for low-cost, compact, robust, and highly integrated TDS, THz imaging, and tomography systems.

© 2013 Optical Society of America

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