Laser Modules with High Power & Efficiency

We develop and assemble the appropriate light sources for applications that require high output powers with simultaneously high efficiency. For example, for use as pump lasers in space applications, we focus the laser beam by means of lenses in order to couple it into an optical fiber. Diode lasers (single emitters or laser bars), which are used in materials processing among other applications, are stacked to achieve output powers in the kilowatt range.  In miniaturized micromodules, we combine the emission of several semiconductor lasers by means of wavelength multiplexing and/or polarization coupling.

Diode laser stacks

Laser diode stacks consist of vertically arranged laser bars or single emitters. The total optical power thus scales up with the number of emitters to the kilowatt range. Stacks can be used as pump sources for solid-state, fiber and alkali-gas lasers, for example in material processing applications or in high-energy solid-state laser systems. They are also suitable as beam sources for spectrally-combined laser systems for direct material processing. Other applications include free-space communication, printing and medical technology.

Wavelength

  • 650 to 1060 nm, e.g. 940 nm for pumping of Yb:YAG thin-disk amplifiers

Chip technology

  • Semiconductor layers by means of MOVPE
  • Monolithic gratings via surface etch technology or two step-epitaxial techniques
  • Contact windows by
    • projection lithography
    • implantation and isolating layers
    • deposition of metalization
  • Thinning
  • Scribing, breaking and cleaving
  • Facet coating and passivation with extremely long lifetimes

Assembly

  • Soldering of bars and large-aperture single emitters on passive CuW heat sinks
  • Stacking of CuW heat sinks and fixing using AuSn solder suitable for extremely long lifetimes
  • Attaching of FAC (fast-axis collimator) lenses on the stack
  • Coupling into fiber

Typical data

  • QCW operation t= 1 ms f = 10...200 Hz
  • Tailored single emitters with 1.2 mm aperture
    • reliable output power > 120 W
    • power density ~ 1 kW/cm
    • lateral far field 12° (95% power)
    • efficiency > 60%
  • Stack of 28 bars and FACs
    • output power 3.5 kW with efficiency > 60%
    • simple and efficient coupling into fibers possible
      • vertical divergence (> 95% power level) < 2 mrad
      • vertical beam parameter product < 90 mm·mrad
      • lateral divergence (> 95% power level) < 210 mrad
      • lateral beam parameter product < 90 mm·mrad

High-power micromodules

In our compact high-power micromodules, we combine the emission of several semiconductor lasers by means of wavelength multiplexing and/or polarization coupling. This allows high optical output powers to be realized with excellent beam quality. These modules can be used as pump sources for solid-state lasers as well as for direct material processing.

In addition to the optical concept, the thermal design is decisive. The hybrid integration of active and passive elements is realized by means of precision assembly on individually adapted inlays. In addition, electronics for pulsed operation and fiber coupling (single-mode fibers, 20-µm low-mode-number fibers, or multi-mode fibers) can be integrated.

With a compact design, the micromodules deliver:

  • High optical output power of up to 35 W (free-space beam)
  • Excellent beam quality (M² < 3)

Our current projects

Our lasers are used in satellites for space-based sensor technology for climate research. In the MERLIN mission, which is led by the French and German Space Agencies, a light-radar system (LiDAR) will be used to map the concentration of methane gas, which is harmful to the climate, in the Earth's atmosphere.

Lasers for Space & Satellite Applications

BMBF joint project HECMIR under the KMU-NetC programme, coordinated by the Berlin-Brandenburg Competence Network for Optical Technologies (OpTecBB).

Together with small and medium-sized companies, research institutes from Berlin and Jena are developing the world's first pulsed Joule-class laser light source for the mid-infrared spectral range. In the joint project, a diode-pumped solid-state laser with 1.9 μm wavelength that provides high laser energy in the Joule range is to be developed and demonstrated for the first time. This laser source offers a high innovation potential for applications in the medical sector, in material processing and in basic research. Due to several fundamental challenges, such a powerful pulsed laser source is not yet commercially available in this wavelength range.