News: Optoelectronics
4 June 2025
Fraunhofer IAF develops semi-automated manufacturing process for cost-efficient resonantly tunable quantum cascade laser modules
Resonantly tunable quantum cascade lasers (QCLs) are high-performance laser light sources for a wide range of spectroscopy applications in the mid-infrared (MIR) range. Their high brilliance enables minimal measurement times for more precise and efficient characterization processes and can be used, for example, in chemical and pharmaceutical industries, medicine or security technology. Until now, however, the production of QCL modules has been relatively complex and expensive.
The Fraunhofer Institute for Applied Solid State Physics IAF of Freiburg, Germany has therefore developed a semi-automated manufacturing process that significantly simplifies the production of resonantly tunable QCL modules with a MOEMS (micro-opto-electro-mechanical system) grating scanner in an external optical cavity (EC). The MOEMS-EC-QCL technology was developed by Fraunhofer IAF in collaboration with the Fraunhofer Institute for Photonic Microsystems IPMS.
Picture: Three generations of MOEMS-EC-QCL modules (from left to right).
The laser technology is characterized by very broad and extremely fast spectral tunability, enabling real-time spectroscopy and inline measurement systems in various industries. The process significantly accelerates the modules’ manufacturing and reduces its costs.
Inline measurements in industrial processes
“The market potential of MOEMS-EC-QCLs is enormous. The high brilliance, in combination with spectral tunability due to the use of MOEMS diffraction gratings, enables the further development of measurement methods based on Fourier transform infrared (FTIR) spectroscopy and their use for inline measurement technology,” says Dr Marko Haertelt, leader of the Laser Measurement Technology Group at Fraunhofer IAF.
“We have now been able to bring the technology to an industry-ready level in terms of cost and availability: on the one hand, by placing the production of MOEMS-EC-QCL modules on a semi-automated manufacturing basis; on the other hand, by using a scalable approach to couple modules with complementary spectral ranges,” Haertelt continues. “The latter significantly reduces the number of different modules required to cover the entire MIR range from 4µm to 11µm, achieving the necessary economies of scale.”
Semi-automated production of quantum cascade lasers
The high manufacturing costs are the main obstacle to the widespread use of MOEMS-EC-QCLs: Until now, it was only possible to assemble the modules by hand because they had to be actively adjusted. The new process automates the MOEMS-EC-QCL assembly process in essential parts with the help of a pick-and-place system, which significantly reduces manufacturing costs.
In addition, Fraunhofer IAF has developed a flexible and scalable method for efficiently combining multiple laser sources into a multi-core system. Individual QCL modules have only a limited spectral width. By combining modules with supplementary spectral ranges, application-specific multi-core systems can be configured that achieve effective spectral measurement speeds of more than 1 million wavenumbers per second.
Picture: Fraunhofer IAF’s multi-core system with four semi-automatically manufactured MOEMS-EC-QCL modules.
Due to more efficient assembly and combination processes, the advantages of QCL technology are to be made widely available for the first time, particularly to small- and medium-sized enterprises (SMEs), says Fraunhofer IAF.
Advantages and areas of application of MOEMS-EC-QCLs
MOEMS-EC-QCLs are characterized by broad spectral tunability in the mid-infrared wavelength range between 4µm and 11µm and high spectral brilliance. They are suitable for a wide range of spectroscopy methods (transmission, backscattering, ATR, microfluidic, point-of-interest spectroscopy) and allow complete infrared spectra to be recorded in just 1ms.
Potential application for MOEMS-EC-QCLs are correspondingly diverse: They can be used, for example, in semiconductor measurement technology to determine epitaxial layer thicknesses and their compositions, in process analytics to optimize chemical reactions, in process control to test coatings, in security technology to detect hazardous substances or intoxicants, and in the pharmaceutical industry for quality assurance.
Multi-core system at Laser World of Photonics 2025
To demonstrate the newly developed manufacturing and combination processes for MOEMS-EC-QCL modules, in booth 431 (Hall A3) at the Laser World of Photonics 2025 in Munich, Germany (24–27 June) Fraunhofer IAF is presenting a multi-core system multiplexing four semi-automatically manufactured MOEMS-EC-QCL modules (plus associated peripherals) that achieves effective spectral measurement speeds of over 1 million wavenumbers per second.
