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 leafs 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
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All results are published with the permission of the FZ Jülich, ISG, and have been published in Journal of Applied Physics 98 (2005), 14910.
Figure 5:
CST Article "Terahertz broadband metal-dielectric near-field antenna"
last modified 30. Oct 2006 11:58
printed 6. Oct 2008 6:45, Article ID 276
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Article ID: 276
Last modified: 30. Oct 2006 11:58
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