How do mechanical oscillations interact with electromagnetic oscillations? Prof. Silvan Schmid from the TU Vienna has been dealing with this question for years. At the Institute for Sensor and Actuator Systems (Faculty of Electrical Engineering and Information Technology) he and his team are working on microscopically small sensors in which the subtle interplay between very different types of oscillations is exploited.

"Infrared detectors are indispensable in many fields," says Silvan Schmid. "They are needed in chemical analytics, environmental analytics, quality control in the pharmaceutical industry, or even for basic astronomical research. However, it is difficult to manufacture highly sensitive sensors that react to infrared waves. Ordinary photodiodes, such as those used for digital cameras, do not perform well enough in the infrared range.

However, at the TU Vienna a completely different concept is used – nanomechanics: A tiny membrane, only a few nanometers thick, is coated with a thin layer that absorbs infrared radiation particularly well. When infrared light falls on this membrane, it heats up and thereby changes its oscillation frequency – similar to how the sound of a drum changes slightly when the drum membrane is heated.

"By recording this mechanical vibration behaviour electronically, we can determine whether the membrane has been illuminated with infrared radiation – and with unprecedented sensitivity," says Silvan Schmid. In addition, previous detectors had to be brought to very low temperatures – the new sensor should be able to be used at room temperature without any cooling at all.

Decisive preliminary tests have already been successful. "We now know that the concept works," explains Silvan Schmid. "Now it's about developing a working prototype that can be commercially exploited."

Source: Technical University Vienna / Florian Aigner