Packaging influence on laser bars of different dimensions

Abstract

The reliability of high-power diode laser bars is limited by the thermo-mechanical stress occurring during the packaging process and operation. The stress is caused by the mismatch of the thermal expansion coefficients between heat sink and laser bar. In general the stress influence grows with the bar size. The development of tapered laser bars leads to higher cavity lengths so the thermo-mechanical stress in the longitudinal direction becomes more important. In this work the packaging influences on different sized laser bars are compared. At first thermal and thermo-mechanical influences are evaluated in FEM-simulations. Afterwards laser bars of different lengths and widths are mounted and characterized. The occurring strain is analyzed by electroluminescence using the correlation between stress and polarization properties of the laser bar radiation. Because of the correlation between temperature and wavelength, a thermal analysis of the mounted laser bars can be done by emitter resolved spectra scanning. The influence on reliability is analyzed in an aging study with intermediate characterization steps.

Burn-In Aging Behavior and Analytical Modeling of Wavelength-Division Multiplexing Semiconductor Lasers: Is the Swift Burn-In Feasible for Long-Term Reliability Assurance?

“…The Ith change follows the linear regression line, suggesting the same degradation mechanism without inducing new failure modes. For a given burn-in current density, the Ith change is higher for the l000 micrometer long lasers, likely due to the long cavity and mechanical stress [12][13][14][15][16]. For the long cavity, the number of defects within the laser cavity is likely to be higher.…”

“…For the long cavity, the number of defects within the laser cavity is likely to be higher. In addition, the mechanical stress caused by the mismatch of the thermal expansion coefficients between the InP laser chip and AlN submount becomes more important as the laser cavity increases [13]. Hence, the degradation rate is expected to be higher.…”