In this research we have taken advantage of near-field scanning optical microscopy, a recently developed technique, to test the optical nature of GaAlAs semiconductor laser diodes working at 780 nm. With this method, both the images of the topographic and the near-field intensity of the laser diodes can be simultaneously obtained. With the obtained results, we can analyze the variety of the geometric structure, the local near-field optical intensity, the propagating modes, and the near-field mode-field diameter at different working states of the laser diodes. Hereby, we can find the factors that affected the radiation cavity of the laser diode and explore its alive state. © 1999 American Institute of Physics.
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