Półprzewodniki azotkowe jako podstawa dla zielonych laserów VECSEL – przełamywanie "zielonej bariery"

The primary objective of this project is to develop high-beam-quality and high-power green light-emitting lasers in the form of Vertical Extended Cavity Surface Emitting Lasers (VECSELs). Addressing the "green gap" problem, this project aims to create efficient semiconductor light emitters within the spectral region of 450-650 nm, a range traditionally challenging due to various factors such as direct-to-indirect bandgap transitions in Phosphide/Arsenide compounds and increased strain in InGaN quantum wells in nitride semiconductors. To mitigate these challenges, this project will utilize blue laser diodes, known for their excellent parameters, as primary light sources in an optical excitation scheme for VECSELs. This method avoids high-temperature overgrowth by p-type layers, thus preserving the initial quality of the quantum wells. VECSELs, unlike VCSELs (Vertical Cavity Surface Emitting Lasers), are optically pumped, providing significant advantages such as high-quality circular beams, scalable power, and the ability to integrate nonlinear crystals within the cavity for second harmonic generation. Key advantages of nitride-based VECSELs include: 1. Elimination of quantum well deterioration during p-type overgrowth. 2. Simplification of laser technology by removing thick, strained AlGaN cladding layers, resulting in flat epitaxial structures. 3. Efficient carrier injection through photogeneration in quantum barriers. 4. Utilization of ultra-efficient commercial nitride-based blue laser diodes as pumps. This project will be conducted in several work packages, each addressing different technical aspects: - WP1: Epitaxial growth of VECSEL structures using a Metal Organic Vapor Phase Epitaxy (MOVPE) system, followed by characterization via x-ray diffraction, Transmission Electron Microscopy, and Secondary Ion Mass Spectroscopy. - WP2: Development of methods for fabricating concave mirrors on the wafer backside and coating them with highly reflective dielectric coatings. - WP3: Technology development for heat dissipation by soldering chips onto diamond/SiC submounts to manage the significant heat generated by the VECSEL structures. - WP4: Construction of an optical pumping setup for device characterization, including a sample stage with a microchannel cooler, a stabilized temperature holder for the pumping laser, and various measurement systems to evaluate photoluminescence and lasing properties. The project team consists of experienced researchers from the Institute of High Pressure Physics, including Prof. Piotr Perlin, Dr. Łucja Marona, and several collaborators and a PhD student. The team members have extensive backgrounds in nitride semiconductors, optical properties, and laser technology, supported by numerous relevant publications. Despite being a high-risk venture, the project incorporates detailed risk mitigation strategies to address potential challenges. These include adjusting growth parameters, selecting appropriate pump lasers, and fabricating multiple mirror variations to optimize performance. This project promises to advance the development of efficient green light-emitting VECSELs, contributing to the broader goal of overcoming the green gap and enhancing the performance of semiconductor light emitters in this challenging spectral region.