Miniature laser systems to search for traces of life in space

(ORDO NEWS) — Was there life on Mars? This is the question the European Space Agency (ESA) is trying to answer with its ExoMars mission.

Part of the mission is an interesting analytical system designed to work in space and created as part of research work carried out at the IOF Fraunhofer Institute for Applied Optics and Precision Engineering.

Researchers from Jena have developed a miniature laser module for the mobile laboratory of the ExoMars Rover. The institute will be exhibiting this 50-cent-sized diode-pumped solid-state laser Raman spectrometer at the Laser World of Photonics in Munich from 26 to 29 April.

The Rosalind Franklin rover will analyze mineralogical compounds on the surface of Mars, located at a distance of about 56 million kilometers from Earth, in order to search for traces of extraterrestrial life on the planet. To do this, the device is equipped with an onboard drill and a number of scientific instruments.

One of these instruments is a device called the Raman spectrometer. It can be used to analyze the propagation of light from molecules, such as in the atmosphere, or from solids such as rock samples.

The centerpiece of the spectrometer is a highly miniaturized and space-suitable laser source, a diode-pumped, frequency-doubling solid-state laser developed at the Fraunhofer Institute of Physics in Jena.

The Raman spectrometer works as follows: Laser light is emitted, which interacts with the analyzed material. This causes the so-called “Raman effect”. The energy of light goes into the material and back. This changes the energy of the light by changing its wavelength.

The light is then scattered back into the spectrometer where changes in wavelength are analyzed. From the difference between the new frequency and the original frequency of the emitted light, conclusions can be drawn about the composition of the material.

The green laser, built in Jena, operates at a wavelength of 532 nanometers and has a power of over 100 megawatts. “In total, our researchers spent seven years developing the module in order to adapt it to the specific tasks of working in space,” explains Dr. Eric Beckert, project manager for the ExoMars laser at Fraunhofer IOF.

One of the common challenges for projects operating in space is the need for components to be especially small and light. For example, a laser, including its body, weighs only 50 grams, which is equal to half a bar of chocolate.

But, despite the miniaturization, it should provide the same level of performance and reliability. Sensitive optical components must withstand temperature extremes from -130 to +24 degrees, significant exposure to radiation in space, as well as strong vibrations during launch and landing of the rover.

Conventional methods for assembling optical components are not suitable for such extreme conditions. “Therefore, we bonded all the components of the sensitive laser resonator and the secondary optics together using laser soldering,” Beckert explains.

“This provides particularly high stability in the face of thermal and mechanical stress and intense irradiation.” Working with the Spanish laser manufacturer Monocrom, the Jena institute has built a total of five structurally identical lasers over several years for use in a Raman spectrometer. The researchers now hope that their technique could soon be launched into space along with a mission to Mars.

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