Reliability Investigations for High-Power Laser Diodes and Bars

Qualification of laser diode design and technology

Reliability test laboratory
Reliability test laboratory
  • Determination of Degradation Rates  10-5/h in aging tests at 15°C  T ≤ 80°C and t > 1000 h
  • Test Equipment:
    • Current control for CW and QCW operation
    • 10 places - CW up to an optical power of 100 W (bars)
    • 130 places - CW up to an optical power of 40 W
    • 150 places - QCW – duty cycle smaller 10%, peak current 300 A
    • 10 places - dual contact for tapered lasers up to 40 W
    • 10 places - four contacts for hybrid laser systems
    • 45 places - BA and RW laser up to optical power of 4 W
    • 120 places - burn-in up to 10 A
  • Relative power measurement with 1% accuracy within 1000 h

Nondestructive failure analysis

  • Electroluminescence
  • Facet microscopy
  • Spectra analysis below threshold
Reliability tests - medical applications
Example 1 - reliability tests of lasers for medical applications
Reliability tests - hard-pulse conditions
Example 2 - reliability tests under hard-pulse conditions
Determination of acceleration parameters
Example 3 - determination of acceleration parameters

Example 1: Reliability tests of lasers for medical applications

  • Lifetimes larger than 1,000 h necessary
  • 630 nm - 760 nm requested for photodynamic therapy
  • Shown example: 650 nm devices with 100 μm x 1.5 mm
  • Test conditions: constant optical power 1.2 W at T = 15°C

Example 2: Lifetime test under hard pulse conditions

  • Reliability test of diode lasers and bars with full thermal cycling
    • Maximal current - 10 x 100 A, 130 x 45 A
    • Switching frequency below 1 Hz
  • Shown example: 980 nm broad area lasers 90 μm x 4 mm
  • Test conditions: 15 A current pulses, 0.5 Hz at T = 25°C

Example 3: Determination of acceleration parameters

  • Accelerated life test of laser diodes over 20,000 h
  • Three lots of different stress conditions (1 - 1.5 W, 45 - 60°C)
    • observed failures are plotted in log-normal scale
  • Model of accelerated ageing: life time P-β exp(EA/kT)
  • Evaluation of acceleration parameters by maximum likelihood method: E= 0.28 eV, β = 2.33