Stacks

Scheme

Laser diode stacks consists of vertically arranged laser bars or single emitters. Thus the overall power scales with the number of emitters to power in the kW region.

Applications

  • Pumping of solid state, fiber and alkali-gas lasers (e.g. material processing and high-energy-class solid state systems)
  • Direct material processing (e.g. sources for spectral beam combined systems)
  • Free-space communications
  • Printing
  • 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 lenses on the stack
  • Coupling into fiber

Typical data

  • QCW operation tP = 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
    • 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