Development of electrically pumped vertical external cavity surface emitting lasers (EP-VECSELs).

In this thesis design, development and realisation of a substrate emission electrically pumped vertical external cavity surface emitting lasers (EP-VECSELs) emitting in the 980 nm wavelength range is discussed. Chapter 1 provides a literature review of the relevant VCSEL and (OP-VECSEL) technology required for the design of an EP-VECSEL. In chapter 2, different areas of the device design are highlighted, including electrical and optical performance of the distributed Bragg reflectors (DBRs), active region design, device detuning and antirefiective coating design. Chapter 3 provides a description of the method used to fabricate EP-VECSEL devices and focuses on optimisation of different process steps, namely the trench etch profile and depth, as well as the contact metalisation. A method for characterising the detuning of a wafer is also presented. In chapter 4 measurements of fabricated EP-VECSEL are presented, with a method for the characterisation of the EP-VECSEL material by modulating the output coupler mirror reflectivity demonstrated. This method is then used to examine the affect of different substrate dopings on device performance. Data is also presented on beam quality, power scaling and thermal properties. Chapter 5 investigates methods for improving electrical aspects of device operation, with improved nand p DBR designs proposed. In addition, analysis of SIMS data for an EP-VECSEL and n-DBR are presented, along with an investigation of the top contact geometry. In chapter 6 a discussion of the QW active region is provided, first by analysing the epitaxial material used in chapter 4 and then proposing improvements to the growth process. A comparison of a 3, 6 and 9 QW active region is then presented, where the trade offs in the optimum number of QWs are examined. Finally, this thesis is summarised and a new device design is proposed from the findings