Abstract

We demonstrate a rapid scanning high-resolution THz spectrometer capable of acquiring THz field transients with 1 ns duration without mechanical delay line. The THz spectrometer is based on two 1-GHz Ti:sapphire femtosecond lasers which are linked with a fixed repetition rate difference in order to perform high-speed asynchronous optical sampling. One laser drives a high-efficiency large-area GaAs based THz emitter, the other laser is used for electro-optic detection of the emitted THz-field. At a scan rate of 9 kHz a time resolution of 230 fs is accomplished. High-resolution spectra from 50 GHz up to 3 THz are obtained and water absorption lines with a width of 11 GHz are observed. The use of femtosecond lasers with 1 GHz repetition rate is essential to obtain rapid scanning and high time-resolution at the same time.

© 2006 Optical Society of America

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References

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    [CrossRef] [PubMed]
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    [CrossRef]
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Appl. Opt.

Appl. Phys. Lett.

A. Bartels, F. Hudert, C. Janke, T. Dekorsy, and K. Köhler, "Femtosecond time-resolved optical pump-probe spectroscopy at kHz-scan-rates over ns-time-delays without mechanical delay line," Appl. Phys. Lett. submitted (2005).

A. Dreyhaupt, S. Winnerl, T. Dekorsy, and M. Helm, "High-intensity THz radiation from a microstructured large-area photoconductor," Appl. Phys. Lett. 86 121114 (2004).
[CrossRef]

Q. Wu and X.-C. Zhang, "Ultrafast electro-optic field sensors," Appl. Phys. Lett. 68 1604-1606 (1996).
[CrossRef]

R. Huber, A. Brodschelm, F. Tauser, and A. Leitenstorfer, "Generation and field resolved detection of femtosecond electromagnetic pulses tunable up to 41 THz," Appl. Phys. Lett. 76 3191-3193 (2000).
[CrossRef]

T. Yasui, E. Saneyoshi, and T. Araki, "Asynchronous optical sampling THz time-domain spectroscopy for ultrahigh spectral resolution and rapid data acquisition," Appl. Phys. Lett. 87, 061101 (2005).
[CrossRef]

IEEE Trans. Microwave Theory Tech.

D.W. van der Weide, J. Murakowski, and F. Keilmann, "Gas-absorption spectroscopy with electronic terahertz techniques," IEEE Trans. Microwave Theory Tech. 48 740-743 (2000).
[CrossRef]

J. Opt. Soc. Am.

J. Opt. Soc. Am. B

Opt. Lett.

Other

D. Mittleman (ed.), Sensing with THz radiation (Springer, Heidelberg, 2002) and references therein.

J.M. Flaud, C. Camy-Peyret, and R.A. Toth, Water vapor line parameters from microwave to medium infrared (Pergamon, Oxford, 1981).

Supplementary Material (2)

» Media 1: GIF (101 KB)     
» Media 2: GIF (76 KB)     

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Figures (5)

Fig. 1.
Fig. 1.

Experimental setup. Solid lines are optical paths, dashed lines represent electronic signals. See text for details.

Fig. 2.
Fig. 2.

a) Cross-correlation signal between lasers 1 and 2: single scan (dashed line) and averaged over 512 scans (solid line). b) Zoomed view of a THz transient acquired under nitrogen purging of the setup with N=10000 and a total acuisition time of 2500 s. The inset shows the entire data set where the signal is repeated after an inverse repetition rate of laser 2. c) Fourier-transform spectrum of the time-domain signal displayed in b).

Fig. 3.
Fig. 3.

THz transients with water vapor present in the setup at different N and Fourier transform spectra (series of 5 animated frames). [Media 1]

Fig. 4.
Fig. 4.

Water absorption spectra computed from Fourier transforms of time-domain data under nitrogen purging and with water vapor present in the setup (series of 5 animated frames). [Media 2]

Fig. 5.
Fig. 5.

Detailed view of water absorption line at 558 GHz. A Lorentzian fit with a full width at half maximum of 11 GHz is displayed as dashed curve.

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