Lasing characteristics of pillar-type microcavity lasers

Recently, spontaneous emission enhancement in pillar-type microcavities was reported for the first time by the authors.1) This type of cavity structure is relatively easy to fabricate and is suited to large scale integration of surface emitting laser arrays.2) It has been predicted that microcavity lasers, whose cavity size is of the order of one or a few times of the emission wavelength, have the potential for realizing ultralow thresholds (<1μA) and ultrafast modulation (>20GHz).3,4) Ultimately, low threshold lasers imply, to some extent, smaller lasers. To realize such lasers, reduction of losses of carriers and photons due to surface recombination and scattering of light in the cavity structures are very important points. In this paper we show lasing characteristics of micron size cavities up to 2.5μm in diameter. We also show experimental studies of the cavity size dependence of lasing characteristics and microscopic reflection spectra of pillar-type microcavity lasers and discuss their relation to surface recombination and optical losses due to the scattering of light on the sidewalls.