Microsensor that can identify different gases simultaneously

TU Wien has developed a sensor that brings together infrared lasers and detectors which can be used to identify different gases simultaneously

The researchers behind the sensor say it is possible to use the same microscopic structure for both the emission and detection of infrared radiation.

Rolf Szedlak, from TU Wien, explained more: “We make what are known as quantum cascade lasers. They are made up of a sophisticated layered system of different materials and emit light in the infrared range.”

When an electrical voltage is applied to this layered system, electrons pass through the laser. With the right selection of materials and layer thicknesses, the electrons always lose some of their energy when passing from one layer into the next. This energy is released in the form of light, creating an infrared laser beam.

TU Wien’s quantum cascade lasers have a diameter of less than half a millimetre and have properties which mean the laser only emits light at a very specific wavelength. Professor Bernhard Lendl explained that this makes the lasers ideal for chemical analysis of gases as many gases absorb very specific amounts of infrared light. The quantum cascade lasers can be used to detect gases using their own individual infrared ‘fingerprint’.

Another major advantage of the new structure is that it is a laser and detector in one. Two concentric quantum cascade rings which can both emit and detect light are fitted for this purpose. One ring emits the laser light which passes through the gas before being reflected back by a mirror. The second ring then receives the light and measures its strength. The two rings then switch roles to allow the next measurement to be carried out.

The new sensor successfully differentiated between isobutene and isobutene – two molecules that possess very similar chemical properties.

Gottfried Strasser explained more about the potential of the new sensor: “Combining laser and detector brings many advantages. It allows for the production of extremely compact sensors, and conceivably, even an entire array – i.e. a cluster of microsensors – housed on a single chip and able to operate on several different wavelengths simultaneously.”