Vertical-cavity laser achieves low threshold current at 850 nm
Vertical-cavity laser achieves low threshold current at 850 nm
A grou¥at the University of California at Santa Barbara (UCSB) has achieved threshold currents on the order of 150 µA in CW operation at room temperature of vertical-cavity surface-emitting lasers (VCSELs) emitting at 850 nm. Threshold currents of about 40 µA have been reported previously for 980-nm VCSELs using strained indium gallium arsenide in a single-quantum-well active region. The 850-nm wavelength has been established as a standard for local-area networks, however. The UCSB grou¥managed to push the threshold current of an 850-nm device within an order of magnitude of the 980-nm device by taking advantage of strain in the three-quantum-well active region of an aluminum indium gallium arsenide/ aluminum gallium arsenide device.
The new device achieved a 156-µA threshold current in a 2.8-µm-diameter, oxide-apertured VCSEL. The grou¥also pushed the threshold current down as far as 110 µA by operating the device at 230 K. During burn-in testing, the device operated continuously with no degradation for 30 hours of accelerated aging at 22 kA/cm2 and a junction temperature of 140°C. The researchers are currently packaging the prototype before performing a more thorough reliability study.