Effect of high-frequency current modulation on speckle suppression in semiconductor lasers

This paper describes a novel solution for speckle suppression based on high-frequency current driving, wherein the current alternates between threshold and rated levels. The speckle suppression effect achieved through spectral broadening and current pulse modulation was analyzed. The experiment on high-frequency current- driven laser speckle suppression was subsequently conducted using two different types of projection screens. Theoretical and experimental data indicate that the weights of the independent speckle mode superposition and high-frequency spectrum broadening vary with the modulation frequency. As the frequency increases, spectral broadening assumes a more prominent role, while stronger reduction in speckle contrast. This new approach offers a promising solution for improved reduction of speckle in compact projection devices.