The images provide information that helps us understand things in a better way when we see them. Regularly increasing the field of understanding into dimensions that are originally hidden from the naked eye, takes science ahead.
Now, with the introduction of powerful microscopes, we can see into the cells and tissues of living organisms, into the atmosphere of microorganisms as well as into non-living nature.
Light penetrates the specimen and is reflected by internal structures
The imaging method is based on Optical Coherence Tomography (OCT), which has been practised in ophthalmology for several years. At the ophthalmologist, OCT uses infrared light to lighten the retina. The tests are done in such a way that the tissue does not observe the radiation, and it can be reflected by the inner structures.
Yet, the physicists in Jena use short-wave UV light rather than long-wave infrared light for their OCT. This is done to observe the semiconductor material with structure sizes of nanometres, light with a wavelength of only a few nanometres are needed.
The nonlinear optical effect creates coherent extremely short-wave UV light
Producing such extremely short-wave UV light (XUV) used to be difficult and was almost only feasible in large-scale research facilities. Jena physicists, though, generated broadband XUV in a basic laboratory and used high harmonics for this purpose. It is radiation that is composed of the communication of laser light with a medium, and it has a frequency many times that of the original light. The more eminent the harmonic order, the lower the resulting wavelength.
The scientists exposed nanoscopic layer structures in silicon to the coherent XUV radiation and examined the reflected light. The silicon samples comprised of thin layers of other metals, such as silver or titanium, at different depths. Since these materials have complex reflective properties from silicon, they can be recognised in the reflected radiation.
The process is so rigid that not only can the deep structure of the tiny specimens be displayed with nanometre precision, but—due to the differing reflective behaviour—the chemical structure of the specimens can also be determined accurately and, above all, in a non-destructive way. It could be utilised for quality control in the manufacturing process of such nanomaterials, to find chemical impurities or internal defects.
