CST – Computer Simulation Technology

Terahertz Broadband Metal-Dielectric Near-Field Antenna

This antenna-based approach to near-field imaging and spectroscopy can be used for both continuous-wave and pulsed broadband electromagnetic radiation from microwave to terahertz frequencies. The model was constructed and simulated using CST MICROWAVE STUDIO® (CST MWS).

Figure 1: Picture of the near-field antenna

The near-field antenna consists of a rectangular-shaped block of low-loss dielectric material sharpened to a pyramidal tip which is partially metallized and terminated by a micron-sized plane facet.

Figure 2: Field distribution in near-field antenna

At this facet the entire energy of the incident wave is concentrated as a very high but strongly localized electric field, which can be used as a sensitive near-field microprobe for electromagnetic radiation. This is proven by the CST MWS simulation results shown in picture above....

Figure 3: Experimental Setup

Currently, experiments in reflection geometry with pulsed terahertz radiation and continuous-wave radiation near 80 GHz reveal a frequency-independent spatial resolution of about 20 µm corresponding to /200 at 80 GHz, which is only limited by the size of the facet terminating the tip.

Figure 4: 2D Scan of water distribution in plant leaves at 80 GHz Potential applications of this device are:

• Subcell resolution tissue imaging
• THz spectroscopy on single cells
• THz spectroscopy on single molecules
• Contact - free spectroscopic imaging of ferroelectric domains
• Fingerprint detection of very small amounts of hazardous substances
• Spatially resolved pump-probe experiments
• Detection of water inclusion in minerals


All results are published with the permission of the FZ Jülich, ISG, and have been published in Journal of Applied Physics 98 (2005), 14910.

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