Laser development Progress in the field of diode lasers and quantum modules

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Ferd.-Braun-Institut

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The Ferdinand-Braun-Institut is making progress in the development of diode lasers. This includes an improved chip design and assembly technology, which should lead to higher outputs and new applications. The lasers can be used both in industrial production and in research.

Diode lasers are a central component in modern manufacturing and research. They are used in material processing, energy generation and medical technology. The Ferdinand-Braun-Institut (FBH) in Berlin is one of the leading centers for high-power laser diodes and microwave technology.

Experts have been able to make progress in the development of monolithic grating-stabilized diode lasers. This ranges from industrial production to applications such as laser fusion. Improvements at chip level and in assembly and connection technology have led to higher output powers, better efficiency and the provision of new wavelengths. In cooperation with Trumpf, grating-stabilized diode lasers around 880 nm were developed, which achieve maximum continuous wave output powers of 26 W at a spectral width of 1 nm. This power is achieved with DBR (Distributed Bragg Reflector) single emitters with 200 μm stripe width. The lasers are designed for the next generation of industrial pumping applications, in particular for Nd:YAG solid-state lasers.

These diode lasers also lay the foundation for future pulsed applications that require extremely high power. These include pump lasers for generating energy through laser fusion, in which grating-stabilized lasers from 870 to 885 nm play an important role.

A laser system for additive manufacturing

At the heart of the Samba laser system are diode laser modules that emit high output powers at 780 nm. Two of these modules, which consist of stacked individual emitters with an aperture of 1.2 mm each—so-called stacks—are integrated into the compact Samba laser head. This allows the power to be scaled to one kilowatt of continuous wave output power, which hits the workpiece in a precise laser beam with a diameter of 1 mm.

Industrial partners integrate this direct diode laser system onto a robot arm and use it for the efficient additive manufacturing of aluminum in industrial laser wire processing. Due to the higher absorption at 780 nm, the FBH diode lasers developed for this purpose are up to four times more efficient than conventional lasers around 1,030 nm.

The process 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. Thanks to its compact size, it can also be used to produce complex components. The innovative system does not require an optical fiber and is therefore less prone to errors. The wavelength can also be adapted to the desired material absorption.

Analytics, sensor technology and imaging with entangled photons

The FBH is developing quantum light modules based on entangled photon pairs that can be used in a variety of ways. One example is a miniaturized sensor module. The module is the core element of a mobile system that will be used to analyze microplastics on site in bodies of water for the first time. The measurements are carried out exclusively in the near-infrared range (NIR). Neither detectors nor radiation sources in the mid-infrared (MIR) are required. This reduces costs, as detectors and cameras in the NIR range are cheaper than in the MIR range. The system can also be used to detect special plastics in very low concentrations and sizes.

For its quantum light modules, the FBH integrates innovative laser diodes with other elements in the smallest of spaces. An intense laser beam hits a non-linear optical crystal. This ensures that the photons of the laser beam decay into entangled photon pairs—with both photons having different wavelengths. The photon with the MIR wavelength is directed to a sample and back into the sensor module. The photon with the NIR wavelength remains in the module. After the exchange of information between the two photons, only the NIR photons are analyzed. This method is suitable for applications in medicine, metrology, microscopy and environmental analysis.

Miniaturized Master Oscillator Power Amplifier (MOPA)

Researchers at FBH have developed a miniaturized master oscillator power amplifier (MOPA) that delivers a high optical power of more than eight watts in continuous wave operation with a low spectral width (< 100 MHz) and 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 mm x 25 mm, it enables compact and mobile devices.

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 trapezoidal amplifier was selected for the PA. The compact CCP3 mount can be easily installed in measurement setups and systems. As an option, the MOPA can also be integrated into a closed butterfly housing. The wavelengths are flexibly adjustable in the range between 620 and 1180 nm. (heh)