Infrared optics: micro and nanostructures provide new insights

Interview with Prof. Robert Brunner, Department of SciTec, University of Applied Sciences Jena (Ernst-Abbe-Hochschule Jena)

Medicine uses many different forms of energy that remain hidden from our sight: X-rays, ultrasound, magnetic fields, ultraviolet and infrared light. Infrared radiation, in particular, is very versatile when it is generated and measured with micro and nanostructured optics.


Photo: Smiling man with short, graying hair, glasses and suit - Prof. Robert Brunner

Prof. Robert Brunner; ©Robert Brunner

In this interview with, Prof. Robert Brunner talks about the newly established research team "MIRO", the properties of micro and nanostructured optics and where they can be used apart from medicine.

Prof. Brunner, we are talking about the research team "Micro and nanostructured infrared optics", "MIRO" for short. What is its goal?

Prof. Robert Brunner: Infrared radiation is the part of the spectrum that is adjacent to visible light in the long wave range. You can determine the body’s temperature with infrared radiation. It is also possible to detect the properties of materials, molecules and substances. This is just like a spectroscopic fingerprint. Infrared radiation can also be used as a tool like a laser.

Over the past few years, infrared optics have continuously advanced in many different locations. Everything is virtually scattered; there is no central place to go that is able to consolidate the different areas of infrared optics so that a synergistic benefit is being created. MIRO is meant to be this place that unites different partners from the technological field and the application area. The research team consists of the Fraunhofer Institute for Applied Optics and Precision Engineering IOF and the University of Applied Sciences Ernst Abbe here in Jena.

What exactly are micro and nanostructured infrared optics?

Brunner: A human hair has a typical diameter of 50 µm. The typical size of micro or nanostructured optics ranges between 100 µm and 100 nm, which roughly amounts to one five-hundredth the size of a hair. The terms "micro" and "nano" usually refer to the main optical characteristic. A lens is rarely used as a separate element, but rather as part of microlens arrays that contain multiple lenses at the same time. Another example is diffractive optics, whose structure can be envisioned like a smooth lattice. The distance between the individual grid lines is in the micro or nano-range but the overall element is macroscopic in size, comparable to conventional lenses. The characteristics of these lenses are very different from those of macroscopic lenses. You can use them for both light systems and for optical imaging or in spectroscopy.

In the visible spectrum and ultraviolet light wavelength, micro and nano optics are already an established trend. This is not the case yet with the infrared spectrum since there are still unresolved technological challenges in terms of materials, structural features and properties.

Photo: Hand print is secured at a crime scene using coal powder and adhesive film

Infrared optics could be used in forensics in the future. They would be able to make the smallest clues visible and to analyze them; © firea

What is the benefit of producing optics of this scale?

Brunner: You can certainly build optical systems in a smaller and easier fashion this way. Spectroscopic instruments can actually not be created without micro optics. They lack the accuracy to where you simply need the diffractive optical elements.

You can use this in lighting to generate specific patterns that would not be possible with conventional lenses. A typical example that is currently being discussed in the automotive industry is night-vision systems: infrared radiation of animals is utilized to detect them at the side of the road at night. These devices illuminate and at the same time detect the side of the road, and they do so in a customized manner. This is very difficult to do with conventional lenses.

What applications do you primarily envision in the areas of medical technology, biomedicine or laboratory analysis?

Brunner: One special subject that we are also working on is forensic science. Right now, evidence at the scene of a capital crime is presently secured by fixating and collecting it with adhesive film. Two properties of infrared optics are utilized to analyze evidence. This shows the multitude of potential applications.

There is the actual spectroscopic analysis on the one hand. It allows you to analyze a specific element on the foil in terms of its materials and determines whether a detected fiber can be accurately correlated to a specific piece of clothing. On the other hand, infrared radiation can be used as a tool; in this case, to single out a separate element on the foil. This is normally done with a scalpel, which is very involved since you might have very many foils from one crime scene. We can create a small circle on the foil with the help of micro optics and infrared radiation from which this one particular particle can be extracted and directly analyzed.

Applications in medicine are possible wherever you want to detect distinctions, for instance in tissue. During surgery, specific types of tissue could be directly differentiated on site with the endoscope; for instance, by separating healthy from unhealthy tissue. It saves time and energy when you conduct biopsies and it could ultimately also be far more precise than a laboratory analysis.
Photo: Timo Roth; Copyright: B. Frommann

© B. Frommann

The interview was conducted by Timo Roth and translated from German by Elena O'Meara.