Experimental speckle evaluation of broad-area edge-emitting lasers

The speckle characteristics of a broad-area edge-emitting semiconductor laser diode (BAEELD) in continuous wave emission regime are investigated experimentally. Performed measurements aim to assess the dependence of the speckle characteristics on spatial region of emitted light field, driving current and case temperature of BAEELD. When BAEELD operates at operating current of 550 mA and at 24 °C, the speckle in different regions from the broad-area field are measured by three different experimental configurations, including direct measurement, rotating the BAEELD, and gathering all emission by the collimating lens or two mirrors. The correlations between the speckle patterns of different regions of the broad-area field are analyzed. The results demonstrate that the speckle images measured are correlated although the BAEELD operates at different operating currents and case temperatures.