Self heating, edge emitting laser, vertical cavity surface emitting laser
Self-heating leads to temperature rise of laser diode and limits the output power, efficiency and modulation bandwidth due to increased loss and decreased differential gain. The main heat sources in laser diode during continuous wave operation are Joule heating and free carrier absorption loss. To control device self-heating, the epi structure needs to be designed with low electrical resistance and low absorption loss, while the heat flux must spread out of the device efficiently. This dissertation presents the control of self-heating of both edge emitting laser diodes and vertical cavity surface emitting lasers (VCSELs). For the 980nm high power edge emitting laser, asymmetric waveguide is used for low free carrier absorption loss. The waveguide and cladding materials are optimized for high injection efficiency. BeO heatsink is applied to spread the heat efficiently. Injection efficiency of 71% and internal loss of 0.3 cm-1 have been achieved. A total output power of 9.3 W is measured from 0.5cm long device at 14.5A injection current. To further reduce the internal loss, the development of 980nm quantum dot active region is studied. Threshold current density as low as 59A/cm2 is reached. For the VCSELs, oxide-free structure is used to solve the self-heating problem of oxide VCSELs. Removing the oxide layer and using AlAs in the DBRs leads to record low thermal resistance. Optimization of the DBRs leads to low resistance and low free carrier absorption. Power conversion efficiency higher than 50% is achieved. To further reduce device voltage and heat generation, the development of intracavity contacts devices is introduced.
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Doctor of Philosophy (Ph.D.)
College of Optics and Photonics
Optics and Photonics
Optics and Photonics
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Zhang, Yu, "Self-heating control of edge emitting and vertical cavity surface emitting lasers" (2014). Electronic Theses and Dissertations. 1324.