Electrically pumped, room-temperature microdisk semiconductor lasers with submilliampere threshold currents

Electrically pumped whispering-gallery mode microdisk lasers with single-mode operation and submilliampere threshold current at room temperature have been demonstrated. Semiconductor microdisks 10 mu m in diameter and 340-nm thick including four 100-AA InGaAs quantum well layers separated by 150-AA InGaAsP barriers are fabricated with InP support pedestals above (p-type) and below (n-type) the disk. A 4.5- mu m-diameter metal disk atop the p-type pedestal provides electrical contact to the laser structure. The semiconductor disks form high-Q optical resonators for the whispering-gallery mode around the edge of the disk. Electrical pulses 0.3 mu s in length at levels near 1 V and 1 mA result in lasing at room temperature for wavelengths near 1.58 mu m with emission from the edge of the disk. At 1-mA current levels the peak laser emission is 9 dB above the spontaneous emission background and at 8 mA it is 26 dB above the background.