Een Semi-Empirische Benadering van het Optische Ontwerp van een Dunnefilm Perovskiet Laserdiode

Solution-processed materials such as metal halide perovskites have gained relevance in recent years for use in optoelectronic devices. Unlike III-V semiconductors, they can be synthesized in a laboratory using low-cost reagents, and deposited over any surface. Metal halide perovskites possess remarkably good optoelectronic properties which makes them suitable for use in a laser, such as a high carrier mobility and high optical gain. Perovskite films have routinely demonstrated emission of laser light when they are excited using another laser (in a process called optical pumping). Subsequent research is focused on replacing the optical pump with an electrical injection of carriers in these films by contacting them to electrodes and applying a voltage. A key issue faced by lasers using solution-processed media is that the requisite carrier density to display lasing (denoted by a threshold) is very large. While large carrier densities can be excited easily using an optical pump, electrical currents inducing the same carrier density also heat these films strongly. Heating can degrade or even burn these films, creating significant challenges in achieving an electrically pumped laser. Strategies to mitigate this issue and to achieve electrically pumped lasing include engineering better materials to tolerate higher heat and to require a lower threshold carrier density, using fast pulses to prevent accumulation of heat, designing a device with better thermal management, and tuning the optical design of the laser diode to minimize the threshold. This thesis focuses on optical design of a laser diode stack based on metal halide perovskites, with an emphasis on minimization of the threshold in a laser LED. The optical design is enabled using a semi-empirical model, one which uses analytical equations combined with empirical fitting constants to describe the system. Optical properties of the films are characterized and laser designs are benchmarked using an optical pump. First, the characterization techniques are thoroughly discussed, including a detailed explanation of the threshold fluence estimation procedure and a new method for measuring the optical gain. The influence of different design parameters on the threshold fluence of a perovskite waveguide is studied experimentally, and the measurements are supplemented by the semi-empirical model. The study also highlights desirable properties in a perovskite film, and electrical stack design to minimize the threshold in a laser diode. To understand the design principles of a distributed feedback laser, a thorough and systematic experimental analysis of the lasing threshold based on four independent design parameters is performed. The semi-empirical model is also extended to predict the lasing threshold fluence of distributed feedback lasers, within the studied design space. Studies were also conducted over distributed feedback gratings placed above the perovskite film, or beneath the surface of a substrate, to maintain a flat perovskite layer. Finally, the optimized LED stack and distributed feedback gratings are combined to make a laser diode. The semi-empirical model is used to identify the correct laser design parameters, and the optimized laser diode is experimentally characterized. This design strategy, supported by a semi-empirical model, offers a more holistic approach that can be widely applied and easily adjusted for any laser system. It also creates a link between the theoretically calculated threshold gain of a structure, and the experimentally measured threshold fluence or current density of the device.