Ultrabroadband THz – TDS


In our TeraWatt Laboratory we’ve built an ultrabroadband THz time domain spectrometer, capable of performing measurements in frequency range from 0.3 to 20 THz. Depending on type of sample, measurements can be carried out in a transmission or reflection mode – Fig. 1. More over our spectrometer incorporates a third optical beam – pump beam, and is capable of performing time resolved THz measurements with 100 fs time resolution.

Figure 1: (a) Transmission and (b) reflection ultrabroadband THz spectrometer.

In our spectrometer THz waves are generated from two-color laser-induced gas plasma, and then detected using air-biased coherent detection. In this scheme bandwidth is limited only by the bandwidth of the laser.

Figure 2: (a) THz waveform and (b) its amplitude spectrum of the THz radiation generated in two color plasma and detected with ABCD method.

Figure 3 shows example of data obtained our ultrabroadband THz system, with comparison to data obtain conventional THz TDS system based on photoconductive antennas.

Figure 3: Refractive index (dashed line) and absorption coefficient (solid line) of As2S3. The high bandwidth measurements are performed by THz-ABCD system (red) for 13.6 μm thick sample. For comparison the spectroscopy results by photoconductive antenna-based THz-TDS system on thin (black) samples and on a 0.85 mm thick (blue circles) sample. 

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© 2012 Terahertz.dk Our research is carried out at DTU Fotonik - Department of Photonics Engineering, Technical University of Denmark. Suffusion theme by Sayontan Sinha