Experimental research on the performance of a very‐small‐aperture laser

SummaryVery‐small‐aperture lasers (VSALs) with different aperture shapes are fabricated. Their far‐field and near‐field performance is analyzed experimentally. The far‐field performance, including the threshold current, the slope efficiency, the lasing ability and the linear frequency modulation property, is found to be influenced by the front facet reflectivity. A new factor is tentatively proposed to analyze the lasing abilities of VSALs with different aperture shapes. This factor can diminish the discrepancies among the same type laser diodes. The near‐field performance focusses on the confinement effect of the VSAL aperture. A near‐field scanning optical microscopy is used to measure the near‐field intensity distribution from a VSAL. The experimental results indicate that the near‐field performance is affected by the aperture shape. A 100‐nm C‐aperture is proved to be superior to a 100 × 300 nm2 rectangular aperture on both power throughput and peak intensity. These two apertures are fabricated on the same VSAL facet for the fairness of comparison. An optical spot beyond the diffraction limit is also obtained by fabricating a 70‐nm C‐aperture on a VSAL facet.