Low-spatial coherence electrically pumped red-emitting semiconductor laser

摘要

High spatial coherence can maintain the beam stability of the laser after a long distance. However, it limits the applications in laser display including projection and imaging system, because the high coherence of laser diodes cause the artifacts such as speckle. In this work, we design a novel 6xx nm chaotic cavity laser diode, which consists of a D-shaped section used to achieve a large number of independent spatial modes thus reduce coherence and a stripe area to improve power. The radius of the D-shaped cavity is 500 μm and the length of stripe is 1000 μm. The red laser based on GaAs substrate is fabricated by standard photolithography and reactive ion etching process. To obtain an enough optical confinement by effective refractive index step, the etching depth exceeds the active region. The high-power chaotic cavity low-spatial coherence electrically pumped semiconductor laser is first realized with the wavelength around 630 nm. The spectrum width of 15 nm at full width at half maximum (FWHM) and output power of 300 mW is obtained under pulse operation. The speckle contrast is measured to be 5%, showing great potential of reducing speckle from the source directly for laser display.