Ferdinand-Braun-Institut gGmbH, Leibniz-Institut für Höchstfrequenztechnik

Through advancements in chip design and packaging technology, FBH has achieved significant progress with its diode lasers. The output power and efficiency of industrially applicable, monolithic grating-stabilized diode lasers have been increased whilst new wavelengths have been made available for the first time. Among other things, the institute reached record values for diode lasers operating at 880 nm in cooperation with the industrial partner Trumpf. These achieved maximum continuous-wave output powers of 26 watts with a spectral width of 1 nm from grating-stabilized (DBR) 885 nm single emitters featuring a stripe width of 200 micrometers. They are soon be used as next-generation laser bars in industrial production lasers for pumping Nd:YAG solid-state lasers. These diode lasers also lay the foundation for future pulsed applications that require extremely high output powers. These include pump lasers targeting energy generation through laser fusion, a field in which grating-stabilized lasers in the 870 - 885 nm range play an important role. At the heart of the “Samba” laser system, which will also be presented, are high-power diode laser submodules that emit at 780 nm. Two of these submodules, which consist of stacked single emitters each with an aperture of 1.2 millimeters (mm) – so-called stacks – are integrated into the compact “Samba” laser head. This allows the power to be scaled up and hence deliver one kilowatt of continuous-wave output power to the workpiece in a precise laser beam with a diameter of just 1 mm. Industrial partners integrate this direct-diode laser system on a robot arm to use it for efficient additive manufacturing of aluminum in industrial laser wire processing. The FBH diode lasers developed for this purpose are up to four times more efficient than conventional lasers operating at around 1030 nm, due to the higher absorption at 780 nm. The technology will be demonstrated in the first step using a laser wire coating process in which the side walls of high-speed trains are produced with significantly reduced weight. Due to its compact size, the innovative system can also be used to fabricate complex components. It does not require an optical fiber and is therefore less prone to downtime due to fiber breakage. Moreover, the wavelength can be further adapted to suit the desired material absorption.

The FBH develops quantum light modules based on entangled photon pairs that can be used in a wide range of applications. One of the institute's miniaturized sensor modules will be presented at the trade fair. This module is the core element of a mobile system designed to analyze microplastics on site in aquatic environments for the first time. Measurements are carried out exclusively in the near-infrared range (NIR); neither detectors nor mid-infrared (MIR) radiation sources are required. This reduces costs, as detectors and cameras are less expensive in the NIR than in the MIR spectral range. Even the smallest concentrations and sizes of specific plastics can be detected with the system. For its quantum light modules, the FBH integrates advanced laser diodes with further components into the most compact of spaces. Inside the modules, an intense laser beam hits a non-linear optical crystal. This causes the photons of the laser beam to split into entangled photon pairs – with both photons possessing different wavelengths. The photons with the MIR wavelength are guided to a sample and back into the sensor module. While the photons with the NIR wavelength remain inside the module. After the respective photon pairs have exchanged information, only NIR photons are analyzed. This method is ideally suited for applications in medicine, metrology, microscopy, and environmental analysis.

Researchers at FBH have developed a miniaturized master oscillator power amplifier (MOPA) that delivers more than eight watts of optical output power in continuous-wave operation yielding a narrow spectral width (< 100 MHz) and a high beam quality (M² < 2). It can be used in a wide range of applications, from medicine and metrology to quantum physics. Thanks to its small dimensions of just 25 x 25 mm², it enables compact and mobile instruments. To protect the MOPA against optical feedback, it is equipped with a miniaturized optical isolator. The MO is spectrally stabilized by an internal distributed Bragg reflector (DBR), while a tapered amplifier was chosen for the PA. The compact CCP3 mount can be easily integrated into measurement setups and systems. As an option, the MOPA can also be built into a closed butterfly housing. Wavelengths are flexibly adjustable in the range between 620 - 180 nm.