Vertical-cavity surface-emitting lasers'-4 show promise for a variety of applications. High power, low-cost laser sources might result from large coherently-coupled arrays. Small arrays could accomplish high-speed communication between electronic chips, overcoming a bottleneck which presently limits the speed of computers. In the longer term, arrays of laser- based logic gates may be used for photonic switching in communication networks, or for digital or neural computing. In these information processing applications, minimizing the threshold is essential. The lowest threshold edge-emitting lasers5-7 contain a single quantum well and require approximately 0.55 mA. Minimum thresholds will be attained by minimizing the volume of active material in the laser, which in turn requires high- reflectivity mirrors. GaAs-AlAs mirrors grown by molecular beam epitaxy (MBE) have achieved extremely high reflectivity (<99%), high enough to achieve optically-pumped lasing in a vertical cavity with a 80-A-thick single quantum well (SQW) active layer8. Chemically-assisted ion beam etching (CAIE3E) can form waveguiding pillars in such heterostructures with micron dimensions, and optically-pumped lasers with 1.5 pm diameters were demonstrated'. Use of these technologies is effective in fabricating' ultra- small micro-lasers (plasers). In this paper we discuss our initial experiments with plasers, which achieved 1.5 mA room-temperature CW thresholds and up to 8 GHz modulation speeds. We then present all-optical studies (performed earlier) of the characteristics of ultra-small microresonator structures.