Small and large signal modulation of 850 nm oxide-confined verticai-cavity surface-emitting lasers - Lasers and Electro-Optics, 1997. CLEO '97., Summaries of Papers Presented at the Conference on

In just three years since its first introduction,',' the oxide-confined VCSEL has come to dominate much of the semiconductor laser research e f f ~ r t . ~ ~ Its prominence in studies of semiconductor microcavity physics is expected to increase as well, as it represents a promising means of minimizing an optical mode volume. The ease of processing allows novel forms of two-dimensional arrays, and submicron feature sizes. The oxide impact on low threshold VCSEL design can be two-fold. Its use as a dielectric aperture overcomes the lateral size Q limitation, and allows device scaling down to a few microns. Figure 1 shows a plot of threshold current versus aperture diameter for two different aperture designs differing in the oxide aperture thickness (labeled either x = 1.0 or x = 0.97) and placement within the cavity. The apertures are formed in VCSELs by use ofhalfwave cavity spacers and single InGaAs quantum well (QW) active regions, with a lower 26 pair AIAs/GaAs distributed Bragg reflectors (DBRs), and upper DBRs of six pairs of MgFIZnSe. For both types the threshold current continues to decrease with decreasing aperture size down to -2 pm diameter, with a minimum of threshold of -60 FA. For sizes smaller than 2 bm diameter various loss mechanisms lead to sharp increase in threshold. Although the two aperture designs show similar threshold characteristics, the optical modes are found to be quite different for the sub-2 pm device sizes.' 7871 21084