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.

  • Stack element
    [+] Stack element of a 3.5 kW laser stack
  • High-power laser stack
    [+] High-power laser stack with 3.5 kW output power, with lenses

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