Remarkable improvements in vertical-cavity surface-emitting lasers (VCSELs) have been made by the introduction of mode- and current-confining oxide optical aperture now used commercially. However, the oxide aperture blocks heat flow inside the device, causing a larger thermal resistance, and the internal strain caused by the oxide can degrade device reliability, also the diffusion process used for the oxide formation can limit device uniformity and scalability. Oxide-free lithographic VCSELs are introduced to overcome these device limitations, with both the mode and current confined within the lithographically defined intracavity mesa, scaling and mass production of small size device could be possible. The 3 μm diameter lithographic VCSEL shows a threshold current of 260 μA, differential quantum efficiency of 60% and maximum output power density of 65 kW/cm2 , and shows single-mode singlepolarization operation with side-mode-suppression-ratio over 25 dB at output power up to 1 mW. The device also shows reliable operation during 1000 hours stress test with high injection current density of 142 kA/cm2 . The lithographic VCSELs have much lower thermal resistance than oxide-confined VCSELs due to elimination of the oxide aperture. The improved thermal property allows the device to have wide operating temperature range of up to 190 °C heat sink temperature, high output power density especially in small device, high rollover current density and high rollover cavity temperature. Research is still underway to reduce the operating voltage of lithographic VCSELs for high wall plug efficiency, and the voltage of 6 µm device at injection current density of 10 kA/cm2 is reduces to 1.83 V with optimized mesa and DBR mirror iv structure. The lithographic VCSELS are promising to become the next generation VCSEL technology.
| Identifer | oai:union.ndltd.org:ucf.edu/oai:stars.library.ucf.edu:etd-3446 |
| Date | 01 January 2012 |
| Creators | Zhao, Guowei |
| Publisher | STARS |
| Source Sets | University of Central Florida |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Electronic Theses and Dissertations |
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