Size effects in small oxide confined vertical-cavity surface-emitting lasers

Abstract

Data are presented on small area vertical-cavity surface-emitting lasers with lateral sizes ranging from 5 to 1 μm that use both oxide confinement and a high-contrast distributed Bragg reflector as the upper mirror. Optical loss becomes appreciable for device sizes less than 3 μm in diameter, and is analyzed through measurements of threshold, differential output efficiency, and the far-field radiation patterns. The results suggest that loss of optical confinement occurs for thin apertures and small device sizes.

Low threshold vertical-cavity surface-emitting lasers based on high contrast distributed Bragg reflectors

“…3. The increase in threshold current for very small devices is considerably more gradual than what has been recently reported for AlAs/GaAs VCSELs with similar active regions, 16 and indicates that the Al x O y /GaAs DBRs have a decreased optical loss as compared to the AlAs/GaAs system for small optical modes. For example, in another study of VCSELs based on lower AlAs/GaAs DBRs, the threshold nearly doubles from ϳ60 A for a 2 m diameter to ϳ120 A for a 1 m diameter VCSEL.…”

Mesa-size dependence characteristics of vertical surface-emitting lasers

“…This discrepancy of higher power for smaller unoxidized devices may be due to the fact that larger mesa devices require a higher injection current, which, in turn, increases the device temperature. 17 As expected for devices with the same size mesas (23-µm mesa diameter), the oxide confinement device has a lower threshold current as well as a higher light-output power than the unoxidized sample. The slope efficiency is also higher for the oxidized sample.…”

Improved performance of oxide-confined vertical-cavity surface-emitting lasers using a tunnel injection active region

“…This shows that for threshold current densities greater than ϳ1 kA/cm 2 , both the threshold current density and slope efficiency are affected by carrier leakage, which greatly exaggerates the influence of lateral optical loss. 6 In fact, even if the optical loss rate of the confined eigenmode saturates for decreasing aperture sizes, 13 gain saturation and carrier leakage can continue to increase the threshold current and decrease the slope efficiency with decreasing aperture size.…”

“…For very small active volumes, carrier loss over heterobarriers both increases the threshold and reduces the efficiency. 6,7 Recently we suggested that tunnel injection might aid in increasing the electron confinement for small active areas, and demonstrated an oxide-confined VCSEL based on tunnel injection through a double AlAs barrier. 8 However, tuning between the cavity and QW gain region was not optimum, and the double resonant barrier still showed significant electron leakage at high current density.…”

“…To compare the amount of carrier leakage in the tunnel injection VCSEL with the prior /2 cavity VCSEL, 5,6,11 Fig. 6 shows the spontaneous light output versus current density for two devices without the upper MgF/ZnSe DBR.…”