Their research also promises a significant improvement in Terahertz microscopy in the long term, a potentially interesting new imaging technique, and Terahertz microspectroscopy, a technique for identifying tiny quantities of substances using light. Their findings will be published in the scientific journal Optics Express this week.
We know from physics that it is particularly difficult to pass light through a hole smaller than half the wavelength of the light used. With the help of fellow scientists, researchers at Delft University of Technology have managed to provide insight into this process by conducting measurements using what is known as Terahertz radiation (THz radiation). This is far-infrared light with an approximate frequency of 10^12 Hz. This type of radiation allows the researchers to measure the force of the penetrating light’s electrical field near the hole and not, as is usual, the intensity of the penetrating light.
The electrical field’s values reveal much more about how light behaves in such situations than intensity can. Measurement of the strength of the electrical field is done with great precision by measuring the refractive-index of a crystal near the hole using a laser beam. The crystal’s refractive index varies (very slightly) when in a variable electrical field. By measuring the variations in the refractive index, conclusions can be drawn on the strength of the light’s electrical field near the hole.Bouwkamp
Terahertz radiation (with a frequency of about 10^12 Hz) is a type of electromagnetic radiation which is increasingly used to create images. After all, many materials, such as paper, plastics and clothing, are transparent to THz radiation, while they block visible light.
Terahertz microscopes do not yet provide such sharp images. The development of stronger and smaller sources and more sensitive detectors will improve the viability of creating images of, for example, biological cells using THz radiation.
Frank Nuijens | alfa
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