High-power diode laser bars and shear strain

The emitters at the edges of high-power laser bars tend to produce less power than emitters that are near the center of the bar. We suggest that shear strain, which owes to strain induced by bonding, creates through a photoelastic effect a weak birefringence that rotates the plane of polarization of the light. A rotation of the plane of polarization reduces the net gain for the lasing modes and hence leads to a lower output power for the emitters at the edges of the bars, where the shear strain is dominant.